1 & 3 Lean 2 & 4 rich?

Ben

Been Around the Block
need some help with tuning. I'm a newb with this bike. this is a cb500 four bone stock, hasnt run in many many years. Just rebuilt the carbs to original settings. Runs ok, a little sluggish on first 1/4 throttle maybe. Starts ok on starter with choke and once warm, fires up easily, first kick.

Have not adjusted tappets, points or condensors, or replaced plugs.

Observations:

PIPES:
1 & 3 pipes are skin burning hot to the touch (dont ask how I know)
2 & 4 are barely warm
(after warmed up and run for a short bit)

Exhuast 4 sputters moisture, I think its gas, through the drain hole.

Plugs:
1 & 3 look dark and lighten up at the tip, normal or lean?
2 & 4 look dark/black Rich?


If its a rich/leanhow do you adjust for this?
What else should I look for?

Any suggestions?
 
First of all, check your valve clearances and do a compression test to check all is OK in the combustion chamber. Then get a new set of plugs. If the problem is still there, then you can safely say the problem is carb related (seeing as the problem is relating to 1 & 3, and 2 & 4 you can rule out a bad coil or bad points as they would affect 2 & 3, and 1 & 4).

Now check for air leaks in the carb manifolds, check the float levels and do a carb sync (this thing is good: http://www.650ccnd.com/mano.htm ).

If the problem is still there after all this, your carb emulsion tubes might be worn out, or the slide needles worn out, or your idle mixture screws are way off.

Hope that helps ;)
 
hillsy is right on. Also check to make sure your points are functioning properly. They could be burnt or corroded.
 
check again this morning before work. 2&4 are dead cold. Are these 2 cylinders running off the same points/condensors?

When I get home will work through what hillsy outlined.


thanks for the help!
 
are you sure you have the firing order right? stupid q i know but...

sitting on bike, starting from your left 1-2-4-3.
 
not stupid question because i got it wrong
So to revise

Originally
1 - pipe hot
2 - barely warm
4 - pipe hot
3 - barley warm

After I checked Valves & changed plugs
1 - pipe hot
2 - barely warm
4 - pipe hot
3 - pipe hot

Change the plugs out and the right most cylinder (3) pipe now gets hot. So what I have is cylinder 2 (inner left) not hot, i doubt its even firing but I am not sure how to check.

domer said:
are you sure you have the firing order right? stupid q i know but...

sitting on bike, starting from your left 1-2-4-3.
 
Ben said:
not stupid question because i got it wrong
So to revise

Originally
1 - pipe hot
2 - barely warm
4 - pipe hot
3 - barley warm

After I checked Valves & changed plugs
1 - pipe hot
2 - barely warm
4 - pipe hot
3 - pipe hot

Change the plugs out and the right most cylinder (3) pipe now gets hot. So what I have is cylinder 2 (inner left) not hot, i doubt its even firing but I am not sure how to check.


do you have spark on all 4 plugs? check that. if you do, its a carb tuning issue and going through and resetting them all would be best. if a plug is not firing, change points and check again. if its still not firing, change condensors and check again.
 
Don't worry about the firing order - as you sit on the bike #1 cyl is far left, then 2, 3 and 4 (far right).

1 and 4 fire off the same coil / point, 2 and 3 off the other coil / point.

Now, which exhausts are hot and which are cold??
 
Take the time ;D to set the ignition timing.So #2 is cold,,no fuel?? not uncommon for a old bike to have bad ignition wires or plug caps....its only 38 yrs old,,,I've seen this before,, anyways good luck
 
ok, from left to right sitting on the bike

1. HOT
2. COLD
3. HOT
4. HOT was cold originally, replaced all plugs now hot.

Also took a look at the points, there is some sparking between the gap....is this a sign of bad condensors or bad points.

I do have an OEM Honda plate loaded with points and condensors , NOS. Are these factory set can I drop it in and see if makes a difference before working through checking timing, gap, condensors, coils, carbs, sanity. newb with electrics, if there is agood tutorial on the systematic approach to debuggin ignition I would appreciate a heads up. the shop manual is thin on this kinda thing.
 
OK - so cold #2 could be a faulty plug (I've had brand new plugs fail on me before - don't rule it out), or a faulty plug cap / lead. Swap plug leads between 2 and 3 and see what happens. If the problem moves to #3, then it's the lead / cap. If it stays with #2, then it's the plug or a carb issue.

You should see sparking between the contact points when the bike is running - that is normal. And because you are getting good spark from at least 1 lead off each coil that means your points are OK.
 
thanks hillsy, i did the cap swap and same result. Then went through the Points as per the shop manual and that seems to be ok. The plug does spark, checked that.

So moved on to it being a carb. First thing was I loosened off the bowl on #2, dry, no gas. Checked the others and they spill gas when loosened. So the line that feeds 1&2 is delivering gas...

Anything I can do before/without taking the carbs off? And whats the systematic approach once I get them off.

Sorry for the newb questions, I do have a copy of the Shop Manual buts weak on theroy, weak in general.
 
your due for a carb rebuild. get a rebuild kit, pull the carbs, and have at it. Ultrasonic carb cleaning is the best, but carb cleaner and compressed air does a great job also.

you should notice a big difference.
 
Didn't you say you re-built the carbs??

Anyway, it's probably a blocked / sticking float valve. The floats can stick / get hung up on the bowl gaskets - that would be the first thing to check
 
yep, complete carb rebuild was first thing I did, ultrasonic cleaning, the works. Will check that first, and while I have them out will recheck the floats on all of them.

I was a bit confused on how tto measure float height, from where to where, when the floats are sitting up or on their side, any advice appreciated

thanks guys.
 
someone correct me if im wrong, but i measure the float height with them upside down float just resting on the needle, and measure from the bowl mating surface...
 
domer said:
someone correct me if im wrong, but i measure the float height with them upside down float just resting on the needle, and measure from the bowl mating surface...

Correct
 
thanks guys for the help.

I opened all the carbs. the one not running was dry. The rest were wet but whatever...

The one thing I did not do on the rebuild was check the float height properly. I just replaced them as they came out, as all were about the same so i checked the float heights on all of them.

Well they were way high, which I figure means the the bowls were starved for fuel. I lowered them all to 22mm from carb to float just off the spring.

Buttoned it all up, fuck with getting the carbs in, pain in the ass. Then noticed I routed the clutch cable the wrong way. COuld have left it but fuck, I am this far into it why shit out now....

Took it all off again. Buttoned it all up again.

Went for a ride and holy shit this bike is pretty fast. Gotta hold on now. When I first got the thing, I must have been running 3 cylinders only and even then on a lean fuel supply. I figured, ehn pretty pedestrian ride. Now the thing takes off....should be a load fun.

thanks for walking me through it!!!! ;D

on to the charging system
 
how would I go about diagnosing a rich problem and then correct it if it is?

#4 (right outer) is firing and plug is wet but no combustion. some backfiring through the carb I think. some sputtering through the exhaust (4-4) lots of moisture from exhaust drain hole, leaves a small puddle, both sides do this and i dont think its condensation..

Some background. Previous owner had the floats up really high, it must have been intentional as they were all set high. I brought them way back down to 22mm. This would mean more gas would sit in the carb yes?

I also rebuilt the carbs and set the needle to what it was when I took them out. So, if the PO had the bowls high(lean supply) and low needles to compensate, would it make sense that if I return the bowls to normal (more gas), I should have also lowered the needle (leaner mix)?

Not keen on taking apart the carbs but if thats the case, anyone know what baseline settings to set them at?
 
Do you have the manual for the bike? I dont know the baseline settings off the top of my head but it will be in the manual. That is what i would do if i were you, id set the carbs back to factory and then try to tune from there. Its so much harder to tune a carb that someone else has already fucked with, so much harder infact that its almost never worth the effort unless its just like very slightly rich or lean. Since youre are definately not working properly, tear them out and put everything back to factory, and go from there.
 
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