October 2011 8

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

http://www.regulatorrectifier.com/catal … -Rectifier

Would this work with this diagram from your post? I would like to combine the two if possible.

http://cycles.evanfell.com/2010/03/simp … fe-racers/

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!!

Take care

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.

Hey Evan-

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 oil
change spark plugs
clean carbs
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

Cheers

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.

Good luck.

Hey Evan-

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

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?

I have an Suzuki RG125 1993 fully rebuilt and a great runner. BUT it will not start when cold without a hand over the airbox intake to ”choke the engine” then she fires perfectly and runs ok , choke on etc… I have stripped and cleaned the carb loads of times, this tends to fix the problem once then next day same problem. Could the choke tube be semi blocked?, the only bit I can’t take out and clean? Otherwwise the bike runs perfectly,

I have an 83 magna that I’ve cleaned the carbs, adjusted the valves,tested the fuel pump and relay.It will start and idle perfect,but when I ride it it will go a little ways and run out of fuel. I will let it sit for a few minutes and sometimes the fuel pump will prime right away,sometimes it wont.
once it primes, it will go until the bowls become empty again. I feel like I’m missing something,that the answer is right in front of me, but I cant seem to get it. Any ideas or suggestions would be appreciated

Honestly that sounds like a faulty fuel pump to me. Those symptoms are VERY common of a fuel pump that is on it’s way out. I would take a volt meter and put it on the fuel pump, turn on the ignition, watch the voltage, start the bike, watch the voltage, ride the bike, watch the voltage – as long as power is getting to the pump, then the pump is the problem.

However – one thought – if the fuel screens in the tank are clogged up it will limit fuel flow and can cause similar problems. Check fuel flow out of the tank and make sure it’s stable

fuel flow is pretty good out of the tank- sitting still.Do you think it may be possible that the fuel line is resticted or slightly clogged? The pump must have some kind of pressure switch or way of being able to tell when it needs to come on.The bike sat for a while before I got it.I had replaced the original pump with a used one. I am going to try the voltage tests also Thanks for the advice

.

Looks like the fuel pump is a self contained unit in the Honda VF bikes from the early eighties.

I think it’s unlikely that the fuel lines are clogged unless you have an inline fuel filter that is dirty. However, it’s real easy to check – just pop the lines off and blow through them.

My bet is still on a faulty fuel pump.  Why did you replace the original fuel pump? Was it exhibiting the same symptoms?

Another possibility is a clogged tank vent. Try riding with the tank cap open and see if it has any effect.

Evan,I replaced the fuel pump because it would “burp” fuel when idling,I have a glass filter right before the pump. I was told that it was supposed to do that. At that time,I hadnt adjusted the valves yet and the bike would cut off whenever I let go of the throttle. When I first opened the fuel filter the fuel coming out of it was very dirty(cloudy),but now it looks pretty clear.I am going to drain the tanks and try to clean them out. I thought of the tank vent and did ride it with the cap open, but it had no effect.I’m going toput the original back on to see if it has any effect. Thanks for all the advice, I’ll let you know how it turns out.

Hi Evan, I took off the pump and switched it back with the original, and left everything hanging and rode the bike with no problems. When I went to put the pump back in I saw that the fuel line was kinking. It had braided lines that had worn and was allowing it to bend. I replaced the lines and it runs great with no problems. Thanks for the advice. Dave

Glad you were able to solve the problem. I love when it turns out to be a simple solution.

On most of my bikes I replace the stock fuel lines with clear fuel. I usually keep a few feet handy, it’s only a couple bucks to have a length of hose around. Whenever I’m working on carbs I will ALWAYS replace the fuel lines with clear so I can monitor the fuel flow and make sure the fuel is clean.

I just bought 1977 XS 400 without carburator. Can someone please tell me other year of XS will fit or post pic.
Thank you

The 1977-1981 Yamaha XS400 Carbs are the same. They all look like this:

For the record – I think the 1977 XS400 is one of the best looking and most fun riding vintage bikes out there. The XS400 motor is wonderful. Do you have the drum brake version or the disc brake version of the bike?

I got one with disc brake version. I love  the look of this bike and from the picture of yours look about same condition.  And thank you for all information.

I had the dual disk version as well. Fantastic bike!

1 step closer now. I got carb put in my XS, But can’t get her start yet.  I find out there is no spark from both sides of spark wires. What do I have to do from here please help

Assuming your spark plugs are new – First thing to check are your points. Pull off the points cover (the cover above spark plug #1 held on by two phillips heads) and have a look. Are the faces pitted? Worn? Oxidized? Give them a quick look and report back.

I opened up points cover and everythings look very new and funtional. Then I do test spark plugs by pulled out spark plugs, plugged to the wire set close to motor case and try to crank it both plugs were sparked. And I found out 1 side of plug is wet and other side is dry. Please let me know if any idea what  to do

Could be a lot of things. Are you sure the carbs are clean? If one plug is dry it may mean the carb is gunked up.

Does the motor have good compression? Have a compression gauge? If not you can press your thumb down hard on the spark plug hole and kick the motor. If it blows your thumb off the compression is adequate.

How fresh is your gas?

Cleaned all the jets, Got 155 psi of compression after 13th kicks,  Sparked both sides of the plugs and I sprayed starting fluid inside spark holes and cranked up but not start. Is any relay switch such side stand or shut off switch on this bike? Will do more tomorrow.

Well if you are getting spark on both plugs then there aren’t any switches you need to worry about. If you’ve got spark, compression, and fuel it should fire up. Have you adjusted the valves? If the valves are out of whack the bike should still spit and sputter a bit – but maybe they are too far out.

Is your battery fresh? This bike will require a decent condition to run. Your spark will be weak without it.

Thank you Evan
I got it running now, after adjust  and resetting points. I’ll be riding soon

That’s great to hear!

I’ve always liked the process of setting and fine tuning the points. It’s a very enjoyable task for some reason. I like making minor adjustments then ripping down the street and immediately feeling the difference.

Let’s see a photo of your bike!

Notes from a Reader:

This threads pretty cool.  Good to see super helpful people.  Just joined because I fell into an ’81 XS400 Special II (drum brakes) the other day that should make a good project.  It’s got an oil leak I need to fix and probably needs to be recabled.  Anyone know where to get gasket sets for these things?

Are sets like this http://cgi.ebay.com/ebaymotors/Yamaha-X … 500wt_1135

or this
http://cgi.ebay.com/ebaymotors/Yamaha-X … 846wt_1120

Decent?

Congrats on the purchase.

Gasket sets like that are always available on eBay and often times don’t list a manufacturer. I’ve had good results with the generic sets like you mentioned. I’ll typical compare prices with sites like OldBikeBarn and PartsnMore. I don’t have any reservations about the sets you listed. I’ll often use a thin coat of RTV Silicone on many of the gaskets anyway.

If it’s just one gasket you need you might be able to just trace and cut it yourself using some gasket paper from the auto store.

Thanks Evan,
I was thinking of redoing all of them to be honest.  I haven’t ever rebuilt an engine and this seems like a fairly good place to start.  Also, it’s currently leaking oil like a sieve but that could be due to the use of synthetics instead of fossil oil (read your post yesterday.  I’m gonna swap the oil out sometime in the near future and test it.  I’ll probably save myself the trouble of tracing em all out and just score one of those sets.

Any recs for cheap flat track high pipes for one of these little guys?  Maybe a seat?

They are great bikes for sure. I love the XS400 motors – though I prefer the SOHC to the dual cam. They’re all nice though.