How to Clean a Motorcycle Carburetor, the RIGHT way.
Posted on | September 1, 2008 | 46 Comments
I get asked about Carburetor Cleaning regularly both from readers and from friends offline. So I’ve decided to write a definitive guide for cleaning carbs the RIGHT way. So put your tools down for a minute, grab a beer, and give this a read. You might just save yourself a lot of headache and sweat.
Carbs come in many shapes and sizes. Single carbs, dual carbs, racks of 3, 4 or 6, V racks, carbs with ticklers, carbs with accelerators, carbs with asynchronous designs, and carbs that operate vertically. While working on some carburetors is more difficult (due to design) than others, they all share the same basic components, and the process of cleaning those components is generally indentical.
BEFORE YOU START
Make sure that dirty carbs are actually your problem. Lots of things can make a bike run poorly or not start. Weak battery, corroded electrics, old spark plugs, bad timing, low compression, mis-adjusted valves, dirty air filter, and plugged exhausts can all cause poor running. I’ll write an article eventually on how to diagnose poor running conditions shortly, but for now – lets just deal with the carbs.
OK, SO YOUR CARBS ARE DIRTY
Once it has been determined that the carbs are the problem it’s time to get to it. Some racks of carbs are easier to remove than others. If you’re working on a newer model bike the rubber boots from the airbox to the carbs and the manifold boots from the carbs to the motor should be relatively soft and pliable. On older bikes however this is rarely the case.
First remove the fuel tank, seat, and side covers. Depending on your model of bike other parts may need to be removed too. Â For many single cylinder bikes the carb can often be removed without removing any body work at all.
The bike below is a 1983 Yamaha XJ750 Seca with 4 inline Hitachi carburetors
You’ll want to loosen the circle clamps on all of the rubber boots. Sometimes I’ll even take them all right off (carefully, without bending them too badly) so that they aren’t in the way.
Inspect the airbox. On many bikes it is bolted in place to tabs on the frame. Remove those bolts and try to create as much space as possible for the airbox to pull backwards.
Next, put the bike on it’s centerstand and straddle it facing forward. Put your right hand on the right-most carburetor and your left hand on the left-most carburetor and get ready to sweat. Sometimes you’ll be able to pull the carbs straight backwards nice and easy, but that is pretty rare. I usually end up rotating them up then rotating them down as best I can while pulling backwards furiously. This can really take some work and time, especially if you’ve never done it before. In real extreme cases where you simple can’t get the carbs to pull backwards out of the manifold boots I have a couple tips. These tips should only be used in extremely difficult cases when you have been struggling for an hour and simple can’t get the carbs to pull backwards out of the manifold boots.
Tip 1: Ratchet Straps – This is sort of a last resort, but it has worked without fail for me when I’m pooling sweat on the garage floor and the carbs aren’t budging. Wrap a ratchet strap around one of the outer carbs and put the hooks somewhere on the rear of the frame. Then slowly ratchet the carbs right out of the boots. Be careful not to pull them too cockeye’d or you could damage the boots. Attach a second ratchet strap to the other side if necessary. (Note: you can do this in the opposite direction to force carbs back into the boots once they are clean.)
Tip 2: Full Pull! – You should do this before you do the ratchet strap method above. Sit down on your butt along one side of the bike. Wedge one of your feet up between the forks and the front fender, then put both hands on the same outermost carb and PULL PULL PULL! This might not work so well if you’re short! Ha.
Ok, So The Carbs are pulled back
Chances are the airbox boots are all crammed up now. Do your best to rotate the carbs up and out from the boots and pull them out one side of the bike. Sometimes it’s easier to pull the carbs out one side than the other, so have a look to see if there are frame elements, motor elements, or hoses that may block the carbs from coming out on one side.
Also keep note of the throttle cable(s) and choke cable (if there is one). Now may be a good time to loosen the nuts that hold them in place and disconnect them.
Struggle just a couple more minutes wriggling the carbs out the side.
Ok, You have the carbs off the bike
Make sure you brush off any loose dirt or grime, then flip the carbs over and remove the screws from the corners of the carburetor. Some carbs won’t have bolts in the corner and instead have a wire latch over top which can just be forced over.
Remove the bowls.
If the carbs are real gummed up the insides might look like this:
It’s obvious that these carbs are all clogged up. Some carbs might not look so bad, some might be a lot worse. It’s always a mystery what will be inside the bowls.
Now it’s time to remove the floats. It’s generally a good idea to drench everything in carb cleaner (available at any autoparts store). Sometimes the pins will practically fall right out, sometimes they’ll be so stubborn you won’t think they’ll ever come free. But they will! Carefully push on the pin from either side. Sometimes a nail and a gentle tap from a hammer is helpful. **BE CAREFUL**, using force to remove a stuck float pin can break off the pin tower. If they are really stuck and you can’t seem to work them free here are a couple tips.
Tip 1: Heat – Adding a little flame to the float pin towers can help. **Don’t Burn Down Your Garage!!**
Tip 2: Pliers – Using pliers to gently clamp the end of the pin and push it through has worked well for me in the past. **Don’t break the towers!!**
Once the float pin is out you can remove the floats, the float needle, and unscrew the float jet screen.
Set everything aside. Next remove the main jet, pilot jet, and idle jet (if there is one). They should come out easily with a flathead screw driver.
Set them aside.
Next flip the carburetors back over and remove the caps. Underneath the caps is a rubber diaphram with a spring. Sometimes the caps have a tendency to shoot off the top, so be very methodical when removing the screws. Other times the cap tends to stick down until you start to pry at it, then it shoots off, again, just be cautious and don’t loose any parts.
Next you’ll want to gently pull the slides up out of the carburetor body. You can gently pull on the rubber diaphrams, but be very careful not to tear them. If they don’t come up easily stick your finger into the carb intake and push the slide up with your finger. You can also gently pry it with a screw driver (gently). If it doesn’t want to budge don’t force it. Instead finish reading this article and pay attention to the boiling tips further down.
Now your carbs should be pretty well emptied out. If the throttle on the bike moved fluidly and smooth there is little reason to do much to the carb bodies themselves. However, if the trottle was real sticky or frozen there are a few things you can do to free it up. Sometimes just drenching all the throttle components on the carbs and letting it soak is enough, other times it is not. I generally try to break racks of carbs apart. It isn’t often necessary and can be confusing to put everything back together in the right places. Also, the little rubber connector hoses and o-rings have a tendency to crack or leak if you mess with them. If you can’t work the throttle back and forth until its smooth have a look at the boiling tips further down.
Keep it Neat
Organization pays off.
Clean the Main, Idle and Pilot Jets
Hold each jet up to the light and see if you can look through it. The idle and/or pilot jets have extremely small holes so make sure you are looking through them straight. If you can see through the jet it isn’t clogged. There could be a little gunk built up around the edges so spray them down with carb cleaner and let them sit a bit.
If you can’t see through the jet it is clogged and needs to be cleaned. Always try the easiest things first. Here’s an ordered list of a few things you can do to clean the jet.
- Blow through it. – Rarely works, but hey, who knows.
- Compressed air. – Force 100 pounds into it. Works occassionally. Make sure to hold the jet tightly so it doesn’t go flying across the garage. You might put the jet back into the carb body to hold it in place for this.
- Soak it in cleaner. – When I first started cleaning carbs I thought carb cleaner would be the magic answer. It isn’t. In fact, I hardly ever use carb cleaner any more, because it simply doesn’t do a very good job of anything but removing varnish from the bowl and slide. But try this.
- Poking it through. – Collect a few different diameters of needle like objects. A wire from a steel bristle brush works well, a bristle from a broom works well, a baby pin, small sewing needle, etc. Very gently try to poke it through the jet. If you are using a metal needle use caution, brass jets can scratch and deform easily.
- Boiling! – This works better than anything. Toss the jets into a pot of boiling water and let them bounce around for a couple minutes. When you pull them out blow some compressed air through them and you’ll most likely be good to go.
Some idle jets can be real tricky and never seem like they’ll be cleaned out . . . Just keep working at it, I’ve never met a jet that couldn’t be cleaned.
Cleaning the Choke and Air Mixture Screw
Air mixture screws have a tendency to strip or break. If the carbs were real gummed up you might find that the air screws are stuck. Don’t force them, if they don’t want to come out, just leave them for now. It is fairly rare that these screws will need to be cleaned because they are above the float level. If you can get them out just wipe them down with carb cleaner and spray some through the jet.
Cleaning the Slide and Needle
These are easy to clean. Squirt them with a bit of carb cleaner, wd-40, or anything similar, then wipe them down with a rag. Once the varnish is gone they’re good to go. Sometimes they get heavy varnish on them which I will scratch off carefully with a piece of plastic. Scratching the slide and needle is a BAD thing, use caution.
Cleaning the Carb Bodies
Use the same squirt and wipe method noted above. Most of the time the other pressed jets and passages in the carburetors won’t be clogged. But if the bike has been sitting a real long time with squirrels in the airbox it is certainly possible. Us a compressor to blow some air into every passage you can see. Listen for the air coming out the other side. If no air compressor is available use a can of WD-40 with a straw attachment.
If some of the pressed jets are clogged it can be difficult to open them up. There are a few things you can do.
- Carb Dip – Most autoparts stores sell carb dip. It comes in a can similar to a paint can and is a VERY harsh cleaning agent. Soak the entire carbs in this dip. This dip can eat at rubber and plastics if they are submerged for too long, so try and remove everything you can from the carb bodies before soaking them. Once you pull them out swish the carbs around in a bucket of water to clean off the excess dip, then hose them down with WD-40 to get rid of the water.
- Boiling in Water – Not many people do this but it is by far the best way of cleaning carburetors. Dropping the carbs into a pot of boiling water will instantly free up stuck slides, throttle plates, and other frozen parts. It will also loosen the dirt and grime clogging up pressed jets and other passages. Just make sure to dry the carbs thoroughly with compressed air or the sun afterwards.
- Boiling in Lemon Juice – There is NOTHING BETTER at cleaning carbs than a giant pot of boiling lemon juice. The acidity from the lemons eats through everything; gas varnish, oil build up, dirt, grime, etc. Sometimes I won’t even bother doing anything but this – I’ll just remove the bowls, remove the caps, then drop everything into the pot and let it sit for 20 minutes (rotate them a few times). The one caveat to doing this is that you’ll want to wash the lemon juice off the carbs as soon as you pull them out. So have a bucket of water ready, or a can of WD-40 to hose them down. Also note that the acidity has a tendency to put a dull finish on the aluminum bodies of the carbs. This isn’t a problem in most cases, but if you must have everything shiny be prepared to do a little scrubbing and polishing afterwards. It may sound weird, but trust me, I just saved you LOTS of time. (Most dollar stores sell 1/2 gallon jugs of lemon juice, so buying a few gallons will only cost you $6. Plus you can put it back into the bottles afterwards and save it for next time.)
Cleaning the Bowls
This is pretty straight forward. Use any of the methods above to tranform your varnished bowls.
Most carb bowls are simple, just clean them up and they are good to go. But I picked this Hitachi’s for photos because they have a jet built into the bowl. You can see the ‘fifth’ hole along the edge of the bowl, that is actually a thin passage that extends to the bottom of the bowl. This is for the idle jet and is extremely important. If these passages are clogged, the bike won’t stay running, period. Use the same poke, soak, and boiling methods outlined elsewhere in this article. Not all bowls have these passages, only some, if your’s don’t – good for you!
Once Everything is Clean
Now that everything is clean it’s time to put it all back together. Take your time and make sure you put everything back where it came from. WD-40 is your friend. When screwing in the jets don’t over do it, they only need to be seated and snug, do NOT use any force putting the carbs back together.
If the bowl gaskets got goobered up you can put a little RVT on them. So long as the float needles are still in good condition leaky gaskets shouldn’t be an issue. However, prudent carb tinkerers may want to order replacements if necessary.
Once the carbs are back together stuff them back into the bike!
Extra Notes
- Rebuild Kits – This guide did not mention rebuild kits until now. Rebuild kits (consisting of new gaskets, jets, needles, etc) can be purchased for nearly any bike, both old and new. 95% of the time these are NOT needed. I have rebuilt enough carbs to block off main street, and only once have I used new parts. ONCE!
- Carburetor Adjustment – Carburetor adjustment, setup, jetting, and synchronizing is a whole encyclopedia waiting to happen. Those topics are not covered in this article, but I will address them in future articles.
- Carburetor Polishing – External carb asthetics will be important to some, and not to others. Cleaning is all I am covering here, this will be addressed in the future.
- Work Space – Make sure you have lots of space to keep organized. I also like to work on a wooden surface because it absorbs the spilled gas and cleaners rather than pooling.
That’s it! You’re Done!
I’ll continue to write a couple more related articles about diagnosing carburetion issues as well as the proper way to adjust, jet, and tune your carbs.
Comments
46 Responses to “How to Clean a Motorcycle Carburetor, the RIGHT way.”
Leave a Reply
Quick Intro
I have owned nearly every make and model of vintage Japanese motorcycle as well as a number of other Europeans and more modern bikes. I do everything from simple fixes to full restorations. I also travel and ride every chance I get.
My Twitter
- Highway Dirt Bikes new Enduro blinker kits look AWESOME! http://bit.ly/b8YSdH
- The 950 twin used in the USA Highland bike - Swedish sourced I believe. http://bit.ly/ataZHd
- The Original Mondo Enduro Trailer - which I still have yet to see http://bit.ly/bZCDlq
- WOW this is some daring riding! I'd ride it, would you? YouTube - Big Balls Trail Ride http://bit.ly/dwgPgv
- I don't understand the front end on this bike. Is it just for rigidity? Taken in 1981 http://bit.ly/ce0aNL
Subscribe to my feed
Search
Archives
- March 2010
- January 2010
- September 2009
- February 2009
- November 2008
- October 2008
- September 2008
- August 2008
- June 2008
- May 2008
- April 2008
- March 2008
- February 2008
- January 2008
- December 2007
- October 2007
- August 2007
- July 2007
- April 2007
- March 2007
- December 2006
- November 2006
- July 2006
- June 2006
September 21st, 2008 @ 10:23 pm
husband read your carb cleaning article and was delighted. Keep up the sharing. we all benefit. Where is a good tool kit for a 1982 Yamaha xj 750 maxim for purchase to carry on the bike? birthday coming up.
September 21st, 2008 @ 10:24 pm
Excellent
September 25th, 2008 @ 10:44 pm
I’m glad I found this article after much searching on the web for topics on the 1983 XJ750 Seca (same one/color as author’s). This motorbike came into my possession only a week ago. Until I acquire the Haynes manual, I have no clue as to how to check/replace the air filter. Bike is running strong for now though, but I’d like to learn as much about it as I can.
September 26th, 2008 @ 2:09 pm
Thanks for the comments! It makes it worthwhile if a few people take away some good information.
p.napoli,
In my opinion there aren’t a whole lot of good tool kits available anywhere. You can find universal tool kits on nearly any motorcycle parts website, but they frankly aren’t all that great. The best kits will always be pieced together by the owner using the tools he/she likes using to complete any particular mechanical task.
Factory tool kits are often lacking in quality and usefulness. I like to pull my bikes apart piece by piece and set aside every tool I use for the entire process, then I find a way to minimize. The optimum tool kit for me is about the size of a 6 inch sub and will let me do everything from adjusting the valves to changing a tire. Many aren’t quite as confident when working on their machines, so unless there is a real simple fix most riders will just call a tow truck instead of attempting a repair on the roadside.
Anyway, I guess this doesn’t help you all that much, but I would recommend going to a site like rockymountainatv.com and searching around through their tool section. They carry “Tusk” brand products which manufacture a number of excellent combination/multi tools for tool kits. Most Japanese bikes will always need a 8, 10, 12, and 14mm wrench, tire irons, a small vice grip, needle nose pliers, zip ties, electrical tape, chain masterlink, phillips and flat head screw drivers, etc.
sgttom,
Congrats on the purchase. The XJ750 is an excellent motor and will last a long long time. I can’t recall off hand if the airbox opens on top underneath the seat, or on the left side of the bike behind the side cover and electrical components. Either way, replacing the air filter should be a no brainer. Lift up the seat and see if the top of the airbox comes off with a couple bolts, they usually do.
Let me know if you have any other questions.
Thanks guys and gals!
September 30th, 2008 @ 6:42 pm
You make it sound so easy, I truly hope it is. I have stayed far away from Carbs my whole life, about 30 yrs of riding. But now I need to do some 77 KZ650 carbs on a couple of bikes for me and my son. I am going to follow your article and see what happens, I will let you know. Question: one of the bikes is missing some carb parts, float, needle/seat, pin. My local shop says they only go back to 81, do you know where to get some affordable replacement parts ?
TGH
October 1st, 2008 @ 1:12 am
Taylor,
I don’t know if ‘easy’ is the right word to describe it for a first timer. As long as you take time, use caution, and take care to keep your parts organized you’ll be fine. The first couple carb racks I cleaned took me a full day or longer to work through. These days I can pull off a rack of carbs, clean them, and have them back on within a couple hours.
KZ650 carbs are made by Keihin and the tops of them are a little different than the Hitachi’s in my photos. The Keihins use a lever actuated slide and do not have the rubber diaphragm up top. Otherwise you’ll find my article pretty accurate.
You can find spare parts for the carbs (jets, floats, etc) at a variety of vendors that deal in Vintage bikes. Old Bike Barn, Parts n’ More, and several others should all have them. Take a look at the list of Parts Houses I Like on the right side of this page and you’ll find what you need.
Let me know how it goes or if you have any questions along the way.
Cheers,
-Evan
October 14th, 2008 @ 4:08 am
Hopefully all works out okay!the article sounds awsome was hard to find some thing like this on the net about motorbikes.. CHEERS!
October 22nd, 2008 @ 8:27 pm
Great article I read this having never worked on my bike before but money constraints say I had to and WoW this was easier than I thought it would be nice work I ride a suzuki rf900r and my carbs were not bad at all but boiling is the key!!!! the carbs look and run great thanks alot for your help.
Kevin
October 23rd, 2008 @ 1:51 pm
Smiley,
The boiling really does work well. It’s strange to me that it isn’t recommended more by other wrenchers. Just always make sure you get all the water out of every passage before reinstalling the jets and carbs. Water (or lemon juice) in the motor = AHHH!
-Evan
October 24th, 2008 @ 5:36 am
Thank you for your good artical as i had found it to late, but in saying this should be a must for motor cycle mechanics to even read to get them up to spec, I have one of these and had it parked for awhile then they changed from leaded fuel to unlead fuel and had the fuel sperate in the carbs etc. After taking it to a bike shop to get it sorted and tuned etc, had it running like a dog with the flue. Now after going to another bike shop and they allowing myself to carry out the work putting it on the shops dyno and doing the work myself with the time and resorces that I had at the time, the main jets were 105 and now 95s and running sweet on the mains on the dyno in New Zealand. As i said time and resources they didn’t have any primary jets in stock to set up primary’s, what I would like to no before I order primary jets. What would be the right jet to order for this as I have 43s in at the moment and is running to rich should I go to 42s or 40s for a start and work down, have you been here before. As I am not living where I had access to a dyno now and the shop that allowed me to carry out my tuning didnt have the primary jets. I would like to put this to bed for once and for all. I dont want to go to lean or in your advice should I look at a 41. Because what I would like to have is a bike that starts well and runns well at idle with good fuel econmany. Engine Tappet settings are correct and carbs are ballanced correctly, no air leaks etc. The worst thing is about the whole sarga is giving it to a bike shop at the start to get it sorted. Being a motor Mechanic my self entrusting them to now what they are doing in this sort field is a question in it self but that is in the past. What I no now and what I new then is the old learning things in life. Can you please advise if you have been here with tunning these carbs.
Thank you
Phil
November 16th, 2008 @ 12:59 am
OH MANNNNNNN this is a true God send. i have the manual but was a bit perplexed with the whole thing. i have never attempted a rebuild and was a bit reserved about it and even invested in an online carb purchase for a back up for the murphy law effect.(used condition not known yet). having read your guide i was literally informed with some good tricks and found a bit more confidence to proceed. i am starting my cleaning project this w/e and bought many cans of carb cleaner for the preparation. absolutely love the LEMON JUICE idea and the cost too!!!!!!! let you know how it goes for me soon,but wanted to pass along my much appreciated thanks a ton. the google search for the hitachi carb sent me your way and i am indebted to you for the info thanks
November 16th, 2008 @ 10:13 am
may i ask what is the benefit if any of a stage 1 or stage 3 jet kit? i want to redo my 4-2 to a 4-1 exhaust and is this a necessary move for horsepower improvement?
December 20th, 2008 @ 11:05 am
Evan,
Wonderful piece, wish more people out there gave realistic advice like yours. I have rebuilt many carbs, both automotive and motorcycle. I have boiled several carbs in the past, in shops and at home, using non phosphorous parts cleaners and water, but never lemon juice I am going to try that one soon though, thanks for the tip.
What brought me to your site was actually a google search for polishing carbs. I don’t normally worry about this with Keihin’s or Mikuni’s, but I am rebuilding an old BSA with an Amal, and I would like to put a bit of a shine on it as well as polish the slide and internals of the carb body. I read from an old timer that he used rock tumblers on his Amal’s, and now I am torn between the old fashioned way … by hand, and buying a tumbler or vibratory polisher. Any tips ?
Ricky … Stage 1, Stage 2, Stage 3 Jet Kits are marketing terms and used far too loosely towards naïve consumers. The retailer or product manufacturer is making an educated guess as to the best Jet Combination for your application, and in many cases this educated guess is not at all close. There is no substitute for properly jetting your carb to run best with your current modifications, and buying a predetermined Jet Kit is not the final answer. Changing the jet size, will also require re-adjusting the air fuel mixture on every carb, and the seller is assuming your carbs do not need to be flow checked or balanced. Rebuilding a carb and putting it back to factory specs is one thing, but modifications for performance is something altogether more complex. For a better basic understanding of this I highly recommend the Haynes Fuel Systrems Manual (labeled Tech Book) HM3514 ISBN-10: 1859605141 ISBN-13: 978-1859605141
December 24th, 2008 @ 12:53 am
Joseph,
Thank you for all your comments. I agree 100% about jet kits.
I have seen stone and sand tumblers used for cleaning all manner of motorcycle parts, and they do seem to work quite well. If you want a project you can build a nice sized one out of an old propane tank and a cheap electric motor from a scrap yard. – I haven’t the desire to build such a device so I polish my carbs with elbow grease. I find that a dremel tool with a wire wheel on it will greatly speed up the process. The wire wheel will polish it up quite nicely on its own but the finish will be uneven. After the dremel just move on to hand work with wet/dry or polishing compound.
-Evan
January 1st, 2009 @ 8:50 am
hYR37e Thanks for good post
January 15th, 2009 @ 4:42 pm
I loved your article, very informative, but can you tell me why does the gas blow back in to my carburator?
February 14th, 2009 @ 2:09 am
Read your article and purchased 3 sets of “used” Mikuni BS34’s. Using your specific methods, carbs came out as clean as the day they were made. Kept one set for my 83 KZ750 and sold the other two on ebay. Thanx for the valuable info.
~Tony
February 14th, 2009 @ 2:13 am
Oh, and http://www.cyclepartsnation.com has most every part for every bike. Check it out!
February 14th, 2009 @ 9:40 pm
Hello,
I enjoyed the article.I have an 81 Honda cb750 c and am getting ready to rebuild the carbs. Before I do this I am gonna do away with the stock airbox and install the k & n air filter pods and replace my rusted out stock exhaust with a 4 into 1 (originally 4 into 4). I have not been able to find much information about jet kits. Does anybody know what I should go with (brand, stage 1,2, or 3). any advice or input would be greatly appreciated.
February 16th, 2009 @ 9:23 am
Dwight, every bike is going to be a little different. I’m sure you can dig up jet kits for your CB without much trouble, but if it was me I would just check what size jets I had in the bike and go down to the local dealer and pick up a few sizes above what I had. Most dealers will have main jets in stock for $4-6 a piece. I wouldn’t pay any more than that locally. You can find them online for around $2.50 a pop. If you go with the kit you’ll probably want a Stage 2 setup.
-Evan
February 16th, 2009 @ 8:59 pm
Hi,
Read your artical, good reading for a novice like me.
I have a kawasaki gt550 and have been trying to find out why it is running poorly. I was figuring it might be the carbs, tried running some carb cleaner through and didn’t help much.
I took off caps of carbs and each diaphram has a tear in it! Would this be a problem? don’t realy know what they do.
cheers,
tim
February 17th, 2009 @ 7:34 pm
Tim,
YES! If the diaphragms are torn the slides will never operate properly and the vacuum leak will probably interfere with some of the jets as well. You should replace those diaphragms.
Also, as a good rule of thumb – If you don’t know for SURE that your carbs are clean, then they probably aren’t and should be pulled for a cleaning. Adjusting your valves won’t hurt anything either
!
Start by replacing the bad diaphragms.
Thanks
- Evan
February 18th, 2009 @ 8:32 am
All i can say is WOW! i have been using chemdip and carb spray for as long as i remember. i ran across this post in the middle of my carb re-build on my Maxim xj700. only one or two things i diddnt see you mention the hitachi carb setup you have is identical to mine. the rubber tips on he float needle’s and the filter screens behind them.
i am not sure if the boiling will re-vive my float needle’s but i will give it a shot and let you know. at any rate this is one of a few very well written and informational posts i have read in a long time. Thanks for spending the time doing this
February 18th, 2009 @ 8:34 pm
Evan,
Thanks for your response, thats pretty basic stuff I suppose. Will clean the carbs I think. Great site!
regs,
Tim
June 9th, 2009 @ 11:44 pm
A very big thank you for your excellent write up. My 82 Yahama JX750 Maxim had been parked for 3 years. I got it started but it wouldn’t idle or run with out choke. I followed your instructions step by step to clean the carbs (2 pilot jets were completely plugged) and now it runs like a champ. Wouldn’t have had the courage to rip out the carbs clean them and put it all back together with your easy to follow instructions.
May hours of summer ridding ahead thanks to you!
-Rob
June 10th, 2009 @ 1:30 am
Evan: Terrific well written piece. I wish I had a bike to practice on instead of trying it on my own (85 FJ1100). My bike is at the mechanic’s shop (he’s working on the side). He’s going to work on the carbs after he replaces the leaky intake boots. I’m going to watch him and learn and suggest a good hot lemon water bath if the carbs turn out to be dirty.
Is a leaf blower on low speed too powerful for clearing passages?
Thanks again for sharing your knowledge.
July 27th, 2009 @ 11:43 am
Need some advice guys..
I’m rebuilding a Yamaha XJ650…
Just cleaned and reinstalled carb thanks to your expertise. You really went into detail with this. But soon after everything was put back, and connected…I started her up and it roared at full throttle? Wondering if its from too much fuel, stuck cable, or what?
July 27th, 2009 @ 7:09 pm
thank you.
July 31st, 2009 @ 10:35 am
Evan, thanks for your informative blog. I was going to buy a carb kit but your plan saved me the $$$. My Honda 350 CL wouldn’t fire on the left cylinder except just a little at full choke. I used the steel brush wire and spray carb cleaner on two clogged jets and the bike is now running like it should. Thanks again, Jim
July 31st, 2009 @ 1:33 pm
@RXJ650 – A motor racing to full throttle is very often caused by carburetors being far out of sync – this means that some carburetors are getting more air flow than others causing combustion to be uneven across all the cylinders. This is changed by adjusting the balancing screws in between each of your carbs. You’ll need a vacuum tool to do this properly. However, you can usually get somewhat close by pulling the carbs off and adjusting the throttle plates visually so they are all open an identical amount at idle.
Also, your idle could be just set REAL high – check this first.
October 18th, 2009 @ 12:48 am
Hey Evan,
I want to try boiling my carbs in the lemon juice but quick question. Boiling the carbs completely intact (except for bowls and caps), would the temp combined with acidity of the lemon juice effect rubber parts (o-rings, diaphragm)?
Thanks a ton for the article and possible answer,
Matt
October 31st, 2009 @ 4:43 pm
Thanks for a very informative article. I’m working on a trike project using a Honda CX500 i want to change the carbs so i have a sigle carb for a better engine balance and fuel economy. Can you advise me where i can buy a manifold and which carb to use. I was going to make a manifold and use any carb off a 500 or 650 cc. If i can buy this conversion it will save me a lot of time. Thanks for your time. BILL
November 17th, 2009 @ 6:13 pm
I want to thank you also just like everyone else. I whish I would had seen your post before. I just finished rebuilding the carbs on my ZRX1200 and I know I have to do it again after reading the way you do them. the good thing is that your info just gave me the boost to redo them. Excellent post, I can’t wait to see the next one. Keep it up.
November 19th, 2009 @ 6:36 am
I’m also trying to put a single carb onto my CX 500. Bill if you see this do you want to drop me an e mail about your approach to the project.
(pickteam@xnet.co.nz). There does’nt seem to be sufficient space on the standard frame due to the single large backbone frame. That may nit be a problem on a trike however.
December 28th, 2009 @ 6:23 pm
Great article. I bought my buddy’s old ‘84 Magna V45 back in July for a thousand bucks. I’ve been learning how to do all the maintenance and repairs through trial and error as a first time bike owner, usually doing more harm then good but that’s the best way to learn.
I’m planning on tackling the carbs with fresh rebuild kits in a few weeks, and your article is helping giving me a better idea of how to repair.
January 1st, 2010 @ 11:58 pm
Without a doubt the best info for motorcycle repair I have found on the web! Thanks for the great detail with pictures. I think I might be able to pull it off.
January 6th, 2010 @ 4:27 am
Hi i have a rf900 1994 just a question i was gonna clean my carbs as my bike runs ruff then i have 1 cylinder goes down every year – i clean the plugs and they are sooty especially one of them. after cleaning bike runs well for quite a while befoer i redo same process. oh running on hotter plugs too. would this be likey a carb issue?? also have you written your an article eventually on how to diagnose poor running conditions as yet. cheers
January 8th, 2010 @ 10:21 pm
Hi Craig,
This could be a carb issue, but it could also be a few other things.
A sooty plug is generally the result of running too rich in the cylinder, or burning oil. Do you monitor your engine oil closely?
It would be odd if one carb is jetted richer than the others, but your air adjustment screw could certainly be way off on that one carb, or the choke could be damaged or stuck on. You could also have a dirty float needle which is overfilling the bowl and spilling excess fuel into the cylinder. All of these issues could create a rich situation.
It could also be worn rings, or worn valve seals, causing oil to be burned.
-Evan
January 8th, 2010 @ 10:23 pm
@Dave –
Glad to hear. The Magna carbs can be tricky to remove and work on because they are stuffed between the front and rear cylinders. But the general cleaning process is the same.
@Rich –
Thanks!
February 15th, 2010 @ 12:52 am
Even, I have an Yamaha xs850 (1980) that
also has Hitachi carbs. They look almost like
these on your Seca (the bowls are shaped differently). I’ve owned this bike since 1996,
bur it was sitting in garage for a few years.
Last season I put he bike back on the road -
among other things I cleaned/rebuilt the carbs,
pretty much along the lines of your article, except I put new parts into it: gaskets, float needle, jets/orings.
I had a lot of problems with this, for no apparent reason they were leaking gasoline.
After several weeks of playing with them, they stopped leaking (who knows why) and everything was ok.
Last week I restarted the bike after the winter, and of course middle carb is leaking again.
What are the most common reasons for carbs to leak?
I’m aware of these:
1) bowl gasket is crappy
2) float needle doesn’t seal
3) float height is wrong
4) float sinks instead of floating (hole)
Anything else?
Thanks,
DAniel
February 15th, 2010 @ 10:03 pm
@Daniel
When a carb is leaking it can really only be a few things, and you nailed them.
1 – Float is set too high
2 – Float needle is worn or not seating
The gasket doesn’t play a big role – with the bike on the center stand your carbs shouldn’t leak even if there was no gasket on the bowl. It’s up to the float and the needle to stop the flow of gas, the gasket just holds the gas in the bowl when splashing around while driving.
You’ll want to make sure your float pins (that go from tower to tower) don’t have corrosion and are otherwise smooth and clean. If there are any burrs on the pins, or if they are rusted or bent, it can prevent the float from moving smoothly and it will bind up.
Drop the float a bit and give it a try. Older floats sometimes will get ‘heavy’ and won’t float as well as they once did, but dropping them a little below factory specs can make all the difference.
Good luck! Carbs are always an adventure!
February 16th, 2010 @ 9:47 pm
Thanks Evan!
I disassembled the middle carb, and everything
looks nice and clean. the float feels ok, it
moves smoothly, the pin is clean, the height
is perfect (12.5mm), yet it still leaks -
just open the fuel taps, and after 15 seconds
it will leak, even without starting the engine.
I have a feeling that the float pin must be bad; it came from Ebay ‘carb repair kit’, supposedly from Japan, and as far as I can tell it looks good, but what the heck do I know…
I’m tired of these carbs, I just got
Mikuni BST36 from 1997 Triumph triple,
and they fit perfectly, just need cleaning.
It’s not new, but the original Hitachis
are 30 years old now.
I’ll give them a try later this week. The bad thing is I’ll have to scrap the original airbox and switch to pods.
Daniel
February 17th, 2010 @ 3:03 pm
Problem solved – it was an oring on one of the brass fuel lines Ts leaking. I need to replace the orings…
February 22nd, 2010 @ 1:54 pm
Evan, you are a born teacher. You have a fine work of art here. Thanks a million. Do you have a a favorite strategy for a rusty fuel tank? I’m working on two ‘75 Honda cb360’s, my first bikes, here at age 64. All the best!
February 24th, 2010 @ 3:04 pm
Thanks Michael – I’ve been trying to get some new how-to’s on here.
I DO have a method for rusty tank. Pour in a cup of nuts and washers and swish them around over all the surfaces – they’ll take all the significant rust right off. Then just flush out a couple times and you’re good to go. Make sure you take off the petcock first though so you don’t damage the plastic intakes.
Loose change would work fine too, or buckshot, etc.
March 2nd, 2010 @ 1:49 am
[...] got it working. After reading all weekend about cleaning carbs I decided to pull it apart again. How to Clean a Motorcycle Carburetor, the RIGHT way. Evan Fell Cycle Works Great article. I didn't believe that boiling a carb would actually work but sure enough it got my [...]