Ask Evan 240
First of all, let me say that you’re doing a great service to a lot of riders. It is much appreciated.
I bought a 1985 shadow vt500 last summer, and did not receive to much information on the history of the bike. I got it for a bargain, but it has some performance issues. The first issue it had was a seemingly spent battery(it was completely dead), which I promptly replaced, as well as new plugs. It was starting but just seemed to be running poorly overall. I would need to choke up to start even in perfect conditions, and the bike would hesitate often. A few weeks in I noticed a hesitation on the throttle, it would often seem to “skip” in the middle of acceleration. I didn’t do anything about it last summer as I didn’t have a space to work on it, so I just stored it.
I came back two weeks later to put some fuel stabilizer in for the winter, and the bike would not start. I played around with the electrical, the battery was on a trickle the entire time, but didn’t start with a jump either or a bypass of the solenoid. I pulled the wire leading to the plug on one cylinder and ground it to the frame to make sure I was getting spark, which I was, but with the first spark to the frame, the bike started!(hesitantly). I’m assuming I fouled my sparks again, but that seems very odd behavior.
I’m assuming I need a carb clean. And an additional thing, the specs on my tank say it should hold 3 gallons – I have run the bike until there is no more fuel, and topping off the tank would only fill it to 2 gallons. Is it possible that there is really that much gunk in my tank? Or am I missing something.
Besides a carb/fuel system issue, is there anything else that could be causing this behavior? And for normal maintenance, what else should I look at replacing on the bike?
Thanks, sorry for the lengthy post.
Hi Dave – Thanks for signing up, hopefully I can give you a hand.
The hesitation and poor throttle response you were noticing initially sounds like it is likely carb related. Dirty carbs can definitely cause this symptom. A partially blocked jet, or clogged up emulsion tube or needle can create all kinds of wacky running behavior.
You could also have an air leak around the intake – how do the rubber boots between the head and carbs look? On any older bike I usually start with the carbs because in almost every case of working on an older bike, they have always needed a cleaning. It’s very rare that I work on an older bike running poorly and the carbs aren’t at least partially to blame. Yank them out and give them a proper cleaning.
While you’re doing that carefully inspect the intake manifold boots (rubber boots between the carbs and head) for any cracks or other damage.
A proper valve adjustment certainly won’t hurt you at all either.
Start off by giving the carbs a proper internal inspection and go from there.
Also – make sure your air filter isn’t real dirty or full of mouse nests!
I have read on your post and you are welcome to post this question, although i am no english major..
I will start with, i have a 2001 dyna wide glide (FXDWG). it wouldnt run at idle. I cleaned the carb, when i did, i thought that i opened the pilot jet, and by opened, i mean made the hole bigger than it should be, but now i am not sure. I did some reading on it, with our mods on the bike (pipes, ignition mod, k&N filter, and the bike was jetted with a 195 main jet and new slide, i see where most people reccommend using a larger pilot jet, stock is 45, recommended is 46, i purchase a 46 from the HD dealer. here is my problem. the bike will start but runs like crap at idle, its getting way to much gas. If i hold the slide open a little, it idles fine. I have made sure that all openings, canals and everything is spotless. I have the needle out at 2 turns to start, than ended up putting it all the way in, and it does a little better but still way too much gas. back to the jet one second, the needle was set at about 3 1/4 turns, thats why we decided to put the 46 in. after thinking we messed up the 45. anyway. i have taken this thing apart 3 times to make sure everything is cleaned and I am 99.9% sure it is.
A couple of things that i have noticed are that when its stumbling with too much gas going in, and black smoke pouring out, it appears that, as the slide goes up and down its sucking a bit of gas in through the needle valve, or main jet as you may say. it appears that it shouldnt be.
its not overflowing as if the float was stuck, when i was in there it moves freely up and down. any suggestions would be great. and i really like your site, it has been very helpful.
A handful of Harley questions have been floating in lately. Cool! :devil:
Definitely sounds like you have a jetting issue to me. Normally when adjusting jetting you want to start with the main jet and work your way down. It is very unusual that you would up the pilot jet without first (or at least simultaneously) upping the main jet.
I would recommend starting by making sure you main jet is appropriately sized. You should do this by performing a ‘plug chop’. Get the bike going out on the road, find a long gentle upwards slope. Get the bike up to speed in 4th or 5th gear. Then peg the throttle wide open and hold it wide open for as long as you’re able to (8+ seconds). Then immediately pull in the clutch, kill the engine, and coast to a stop. Inspect your plugs and compare them to the plug diagrams found in this forum.
Once you get your main jet set, then move on to the pilot.
I recently bought a 2003 Honda Shadow VLX 600 for my wife as her first bike. It was a real find . . only 500 original miles on it and it looks like it just came out of the showroom. The problem is, as it’s been sitting unused for years, it was pretty messed up: Carb was all clogged and everything was generally gummed up!
I followed your carb-cleaning advice to the letter and boiled it in Lemon Juice, which seemed to work really well. I re-assembled everything and the bike ran great (kind-of) right off the bat. It starts really easy and idles perfectly. It revs-up just fine in the low-end, but as soon as I start to give it more throttle it starts to bog-down and stalls.
Any idea what might be going on here? It’s a California edition bike with the emission control system, and a vacuum carb, which I hate, but I’m stuck with it.
The jets appear to be completely clean, and the insides of the carb look like new, I just can’t figure it out.
Your symptoms are commonly caused by an air leak. Could be a vacuum diaphragm, a hose, or even just the intake manifolds. I would disassemble and inspect the integrity of all the rubber components.
Also – did you verify that all passages and jets in the carb are clear by spraying fluid or air through them?
I read your article about cleaning carbs with lemon juice. Do you drop all four carbs in there with the rubber o rings and all rubber parts or do these need to be removed. I have a 1986 yamaha yx600 radian and gas started coming out of the carburetor.
When boiling carbs it is safe to leave the rubber bits in. Normally I pull off the bowls, floats, and pull out the diaphragm/slide if it’s present. Pulling out those few parts makes sure you can adequately rinse the carbs out after pulling them from the juice. Then just drop the whole rack right in. Just make sure you really rinse them out and hose them down afterwards.
I bought a ’82 nighthawk about a month ago only 2000 miles, clean I was loving it. Till about a week ago when it left me stranded on the side of the road without warning. I was crusing at 70 when the bike just lost power, the bike didn’t actually die till I came to a stop. After checking some things and making some phone calls I tried to start it again, it started back up. About 100 yards down the highway it lost power again. That repeated one more time before I chalked one up to the bike for the day and waited for a friend with a truck. Since then I’ve checked spark plugs, fuel strainer, carbs (although not extensively) nothing seems to clear it up. Some days it won’t start at all some days it starts right up idles fine in the garage even revs at 4000 for 20-30 seconds fine, but ride it 100 yards or so and it looses power and dies. Please tell me you have the golden nugget of truth, this is my first bike and I am itching to get back out on the road. Thanks for your time!
Bikes only need 3 basic things to run – fuel, compression, spark. If I was you I would tear through the carbs thoroughly. Make sure every passage is clear. Make sure the floats operate smoothly and are set to factory spec. Also verify fuel flow from your petcock.
If you have a compressions gauge you should do a quick check. With only 2000 miles the bike should not have any sort of compression issue, but you never know. Rust could have built up in the cylinder. A compression gauge can be bought at Harbor Freight for around $15 or so.
If the carbs and the compression both check out then it’s on to spark.
BEFORE ANYTHING: Make sure your battery is in good condition!!!! I see so many strange problems with bikes due to a worn battery. If your battery is old, or isn’t holding voltage – REPLACE IT!
Let me know how it goes.
Notes from a Reader:
TyoungYL: I have your golden ticket for this one! (But it’s a year late -_-)
EvanFell: you got it right on with your diagnosis – that’s what my mechanic buddy told me too.
Th OP has probably solved his problem by now but I thought I’d give away the answer anyway.
He blew an air cut-off valve diaphragm.
I experienced exactly the same problem last year on my ’84 Nighthawk 450 (32,000 km). My bike lost power in the above explained fashion as I downshifted to slow down for a minivan on the highway. When I tried to rev up nothing really happened.
It started twice more and then wouldn’t start the third time. I was lucky enough to only be about 8 blocks from home (and driving a light bike)
Regardless of the miles operated the ‘rubber’ (elastomer) components of a bike (or anything else for that matter) will degrade. After twenty years many seams, seals, and gaskets is will be weak and/or cracking.
You can get to one of your air-cut of diaphragms by taking the cover held down by two screws off of the side of your carb. You can’t really get at the other side so you might as well take the whole carb off, clean all the gunk out, lubricate it up and put in 2 new diaphragms (don’t just replace one because the other is liable to blow too). Be very careful not to strip any screws because replacements will be tough to get.
Go to Carb Kit Capital dot com to buy the parts you need for about $25 bucks each….. or get the Honda parts for about $95 each. The important, rubber part of the CarbKitCapital diaphragm fit, by the metal actuator did not so I had to file it down to the same size as the original, which was tricky business.
If I had to, I’d buy the cheep ones instead because they seem to be working fine.
Gents here is my crisis. My 76 Honda CB750A has some gremlins in the wiring. Specifically regarding the tail light /turn signals. I hit the signal and the tail light flashes and the signal barely has a glimmer to it. I’ve checked a number of leads but with no luck. Takers on this?
The old CB’s don’t particularly have an abundance of electrical power. If your battery is weak the lights will be dim. If you’re sitting at idle the lights will be dim.
Having a bad ground will of course cause similar symptoms, but so can having old corroded wires, rusted connections, and an old flasher relay and even bulbs.
If you hold the throttle around 2,000RPMs and see good voltage across the battery, and the blinkers are still really dull, then you’ll need to trace all the associated wires and connectors and just clean them up as best you can. Also inspect the bulbs themselves and consider replacing the flasher relay with a new one – they can be bought at Autozone/PepBoys/Napa for $3.
Hey Evan awesome blog n sites.
Question: I have a 1977 Kz650B bought “right”, $250, turning into cafe’. Tore into rebuild and found wire harness to be pretty much a mess. Bike ran okay, (as much as I could in the snow) but when I tore into the bike I ran into bunches of splices I have no idea what for etc. Plus rectifier looks pretty well worn. I found your other wiring diagrams online and had further questions. I would like to eliminate the battery since I have a kick starter and going for the clean/light cafe’ look too. Trying to keep it legal in Ohio so I’d need turn signals, high beam light etc. But other than the those “bare necessities” I’d like to not do more than required. I thought I read you mentioned the possible need for a capacitor if you eliminated the battery? If so where do you put it and what rating? Also do you have a recommendation for a regulator/recitfier to use? Need to put any diodes anywhere?
Your 1977 KZ650 has a 3-phase excited field alternator which will not allow you to run without a battery. You will need to swap it for a 1978+ KZ650 single phase permanent magnet alternator. If you do that you can then run a capacitor in place of a battery. You’ll want a capacitor somewhere in the 50,000ud 16v to 100,000ud 50v range, it won’t matter too much as long as it’s a well made unit.
You’ll also need to be replacing your regulator for one compatible with the permanent magnet unit, and in turn will need a different rectifier as well.
If you want to stay legal then the above isn’t for you anyway. You won’t have good reliable blinkers because flasher units work best with the ballast of a battery, and you won’t meet requirements for having headlights and taillights being able to remain on with the bike off. You’ll need to decide what’s more important to you.
The simple solution is to just run the smallest battery you can find and leave it at that. A small sealed lead acid battery from an electronics supplier can be about the size of 2 decks of cards and will power everything normally (except the starter).
KZ650’s are great looking bikes in my opinion. I don’t think they need a whole lot of work to be cool. Here’s mine (it has the battery ):
Wow, thanks Evan for such a complete answer!
Yea, I think I’ll go with your recommendation and leave the battery in the loop then. You made my life much easier. Nitro may be in this bikes future and a battery would be necessary anyhow then. Found a great site from a guy named Burgerman .
He builds dynos in England really lays out how to build a system if you ever want to read about it. Don’t know but thought you might like this kind of stuff if you havn’t already found this guy. http://www.nitrous.info/motorcycle-nitr … system.htm
I actually had my local NAPA dealer (Still an “Old School” kinda parts store) locating a low profile battery that I think I can tuck under the rear plastic.
I found a Regulator/Rectifier at RegulatorRectifier.com
Would this work with this diagram from your post? I would like to combine the two if possible.
No problem, here to help!
The regulator/rectifier unit you linked too was actually the one for the KZ750. Probably just a simple mistake, the one you want is obviously the KZ650 version.http://www.regulatorrectifier.com/catal … -Rectifier
If you’re looking to save as much money as possible you can get a single regulator or rectifier for quite cheap. Moose sells generic ones as well as a few other manufacturers. But the unit you linked to looks pretty nice.
Yes, my simple wiring diagrams will work for your bike, and virtually any other bike as well. It’s just the basic electrical components needed for a bike to run and have simple lighting.
I haven’t been to Burgerman’s site before but will take a look, thanks for the link.
I’m going to move my photo hosting site to a new server in the next 24 hours, it’s having some memory issues preventing large resolution photos from being processed properly. Will be fixed ASAP!
Cool on the correct part 650 vs. 750. I can say that sites customer service is outstanding. The guy was really trying hard to find the right part for me so I’d like to reward that.
I try and find a balance between being “frugal” on projects and doing the “right thing”. Enhances the chances that next time a I need something they will be there for me.
Yea, I know some KZ pureist would probably like to hang me for cafe’ing this bike too. It’s in pretty good shape, as yours looked really nice for that era. I’ll post some pics once I can. But even primo restored they ain’t worth nothing! , my VStrom while powerful and torquey is a bit of a “pig” sometimes and I wanted to try this project. I live near a couple of tracks here in Ohio where they have classes etc. Thought I’d might try one someday.
If ya ever need some farming or wine info. let me know maybe I can help ya there!
Have fun in Mech-key-co! I once was in the back country at a farm village there on an agricultural leadership program, awesome “REAL” Mexican food and well when ya drink some local “Hooch”, WoW! But we HAD to, otherwise we would not have been being “polite” 2 R hosts!!
Hey Evan I’m Back w/nuther KZ650 wiring question
I got the 650 Reg/Rec but again my wiring skills are better suited to houses and such. I have your wiring diagram for custom motorcycles – chopper/cafe/rat w/Hans edited version and it’s getting me close but my reg/Rec has more wires?
I have the 3 yellow wires to the stator, 1 green to neg. , 1 red to pos., 1 blue to key/switch, but then I have a orange that it says is to go positive brush on rotor or field coil? That’s got me? Instructions go on to say “For motorcycles with brushes in the charging system: the orange wire goes to the (positive) brush (non-grounded). The (negative) brush must be grounded.
Project going well, I’d upload a pic but I’m not smart enough, I’m sending this from a new iPad I won and that is proving challenging enough learning apple-speak!
I have a 1986 Yamaha Virago 1100. It sat for awhile not sure how long though and it didn’t seem to have the power it was suppose to so I changed the plugs and oil and it ran great for a day and half then started acting up and backfiring then lost the power again. When it started I heard a clank inside the carbs I believe this to be the choke or enricher. One cylinder (the rear one) has a fouled out spark plug with black soot all over it. I pulled the carbs and found a vacuum plug broken so I replaced I pulled the bottoms of the carbs and cleaned it up down there then but it back together and put them back on the bike (I noticed that the enricher on the carb for the rear bank was sticking in the up and down postion), and it ran good for a couple of days and has started clanking in the carbs again and lost power as well as backfiring. There is one shop in town out here that works on Yamaha and they have never heard of this problem they said it may be a vacuum problem but they are not sure everything else is more than an few hours away. Is there a way to adjust, rebuild, or do I have to replace them? Is there a conversion kit to go to a manual choke and a single carb?
I think the shop gave some good advice. It sounds like you have an air leak somewhere.
KJS used to make a single carb conversion kit for the Virago 1100’s – not sure if they still do or not. Seems unlikely.
You can certainly rebuild your carbs. Pieces will still be available from your dealer.
I would look very astutely for air leaks. Inspect the intake rubbers, the vacuum hoses, and any internal diaphragms the carbs have. Spray WD-40 or other fluid on with the bike running and see if you can detect a change.
Also, you can download the Yamaha XV1100 Virago Factory Service Repair Manual from my site.
I recently found myself in possession of a pretty low mileage 2006 Suzuki Boulevard s50. I am excited about finally getting my hands on a motorcycle, but unfortunately this bike has been sitting dormant in a garage for over a year, and more unfortunately, I have no idea where to start with getting it running. I ordered the shop manual and should have most of the appropriate tools, but after doing some research on the internet, it sounds like I need some help from a guy like you. Basically, I found your carb cleaning article on your site and was wondering if you had any more articles like that.
My, admittedly inexperienced, intuition are telling me I need to:
Get new battery
change spark plugs
empty old gasoline?
Look at the pistons, cylinders, and rings? – if I have to do this, do I need to take the engine out of the bike? Is it possible to fix these if the bike has just been sitting?
I know time is money, but ANY help you can give me, or even a push in the right direction would be extremely helpful. This is my first bike and I am very excited about getting it up and running. I have some big sights for this bad boy: Step one get it running, Step two make it awesome (http://www.wrenchmonkees.com/bikes.html)
Thanks in advance for your help
That’s a pretty new bike, and it’s been indoors so it probably doesn’t need too much. First thing I would do is get a new battery for it and put it in. Check that there is oil in the engine, turn on the gas, and see if it’ll start. You’ll probably end up needing to clean the carbs and flush out the gas tank, but I usually at least attempt briefly to start the bike before going further. Otherwise your list looks fine. There is no reason to inspect the motor (pistons, cyl, etc) unless there are known problems with it. Just clean the carbs, change the oil, new battery and plugs, maybe a valve adjustment and you should be in business. If you get a repair manual it will be easy to take care of the basics.
Thanks for responding, that’s the best news I’ve heard all year. Any rocket science involved with flushing the gas tank, or just literally take the tank off the bike and flush it out? Carb wise, ill make sure to follow your guide.
Appreciate the help
For flushing the tank, you’ve got it. Just dump it out and fill it back up. You can put the old gas into your car (as long as it’s clean) and it’ll be diluted plenty that it’ll run just fine.
My only word of caution is do your best not to splash the paint too badly with gas. Prolonged gas exposure will eventually cause your clear coat to peel.
Hello, I have a 1982 450 nighthawk that i have owned for 2 years but it has always missfired around 5000 rpm.I have fitted new jets and needles,plugs,coils etc. Also had the generator rewound and pulse tested and still have the same problems. any ideas.?
It sounds immediately to me like a stator or coil issue. It sounds like you’ve looked at both of those – but have you tested the coil with a proper ohm test? And have you tested the stator output at both cold and hot temperatures? How do your pickups look?