CB 360 Acceleration Trouble

My CB360 runs pretty good when cold. When it warms up, it idles ok and pulls good above 3k but the right cylinder has trouble off idle until above 3k. Also, when rolling at a constant speed/decelerating slightly ( both at low throttle) it sounds like the left cylinder is doing more work until I give it slightly more throttle and the right lights up and pulls. At higher RPMs and more throttle it pulls nice and hard. Any ideas?

Here is what I have done/checked:
Rebuilt Carbs (running 108 jets to help with pods, problem was there before and after)
Played with Sync (bench set with carbs out and then synced by ear…same issue)
Adjusted idle mix
Set points
Replaced points
Adjusted valves
Tensioned cam chain
Sprayed manifold boots with carb cleaner when running to check for vac leaks (no change in running speed)
Changed and gaped plugs

Bench syncing is only good for getting the bike running to do a proper sync. If you are keeping the bike, buy a carb sync tool from amazon, (Motion pro, they have it for about $16, look deeper, they list the $25 one first).....a pair of vacuum gauges and the adapter needed from CrazyPJ.

Not a pod hater, but if you have those cheapo Emgo pods, they are blocking air ports at the front of the inlet to the carb. There is no one I have heard of that can get the CV carbs tuned with those crappy little pods. The symptoms you are listing are often caused by those pods.

Is your exhaust normal length with mufflers? Exhaust that exits before the rear axle are too short, and also reduce "drivability".

You say you replaced points. Did you time it with a strobe type timing light? If the left and right timing are not at the same point, then drivability and vibration occur too.

Is your mechanical timing advance working smoothly? That is another area that can cause some of the issues.

mydlyfkryzis said:

Bench syncing is only good for getting the bike running to do a proper sync. If you are keeping the bike, buy a carb sync tool from amazon, (Motion pro, they have it for about $16, look deeper, they list the $25 one first).....a pair of vacuum gauges and the adapter needed from CrazyPJ.

Not a pod hater, but if you have those cheapo Emgo pods, they are blocking air ports at the front of the inlet to the carb. There is no one I have heard of that can get the CV carbs tuned with those crappy little pods. The symptoms you are listing are often caused by those pods.

Is your exhaust normal length with mufflers? Exhaust that exits before the rear axle are too short, and also reduce "drivability".

You say you replaced points. Did you time it with a strobe type timing light? If the left and right timing are not at the same point, then drivability and vibration occur too.

Is your mechanical timing advance working smoothly? That is another area that can cause some of the issues.

Click to expand...

I agree I need a vac gauge, but I have literally adjusted it in 1/2 turn increments from running only on the left to only on the right and it never goes away completely/becomes fully right biased. The right cylinder always has trouble in the 1/8-1/4 throttle range. The exhaust is some sort of BSA style mufflers but full length and I have run it in the shop with no headers and it still acts up. Timing is statically timed but I have timed it 3-4 times with the same result every time so I think it is ok. The advancer was taken apart and cleaned and working.

I checked the pods and they don't block the air ports on the front and just for kicks I tried it without any filter and it did the same thing. I would also think if it was the pods it would make both carbs act up and the left one runs strong the whole range.

I took some video looking down the venturis today and it almost looks like the right side is over fueling when revved. I noticed if I get it to a throttle position where the right starts sputtering and then lift the slide on that side a little it stops sputtering. The exhaust smells like gas on the right when it sputters and the plug is usually blacker than the left. The slide moves freely (even swapped them between carbs with no change) and the diaphragms are new.

This lead me to remember when I had the carb out the first time I noticed the needle jet holder from that carb was damaged. It looked like the end that goes towards the venturi was bottomed out and then overtightened causing it to be somewhat smushed and mushroomed out. I cleaned it up with a file as best I could and put it in the left carburetor and it still ran crappy on the right and good on the left. Is it possible the pressed in brass insert in the carb body is damaged and causing the needle to not seal that jet correctly? Does the needle seal against the pressed in piece or the needle jet holder? Are those pressed in seats replaceable/available?

Left:
http://youtu.be/SksiYPdQLWA

Right:
http://youtu.be/qsG8FqKg2kI
http://youtu.be/R-Z-Xwh3uiw

I think you are on the right track looking at the needle area of that right carb. Clearly something is amiss/damaged with that carb that adjustments to settings make no difference. I would chase up a different carb/carb body and replace.

Seems like the right side is coming up later than the left. Is the diaphragm in good shape? Are the left and right springs for the slide the same height? Is the needle "loose" in the slide? it should be wobbly...?
Finally, are the left and right float levels the same? A low float level means a high fuel level, messing up the mixture.

Also, are the valves adjusted well? The fuel spraying back is from the air reversing direction....

The other problem may be the emulsifier holes on the needle jet and possibly main jet....The small holes in the side of the tube are to aerate the fuel and make smaller drops. The drops look big, so I suspect the emulsifier holes are blocked. If you used other than stock brass, I noticed the holes are much smaller in the aftermarket stuff....Large drops of fuel do not combust well...You get less burnt fuel and the larger drops pass though the combustion chamber without burning...They can foul plugs....It creates the odd condition where there is too much fuel, yet you run like it is too lean.

That's about all I got...

Hell Im most impressed w the videos ! are you using an iphone for those?

everything mydlyf said is gospel.

Check diaphragms for pin holes and cracks. springs will measure 5.25 inches long.

Your bike will not run properly w pods of any style without crazyPJs modifications. And he will properly clean and sync them too.

If you insist on trying to make her run yourself... :

Remove ALL brass from the carbs and clean them properly. A round chopstick works great for pushing out the tube in the main primary circuit. And a wooden chopstick wont damage the pee hole.
Check idle and pilot circuits for proper function.
use a little oil to lube the o-rings, especially on the float seat, for easy installation.
stock float setting is 18.5, mine is 19.5mm, pj recommends 21mm. We both agree 18.5 is wrong.
Ensure slide vents are on filter side. see map below!

Unless you never plan to ride over 50 mph or rev over 5krpm the 108 secondaries will work out great!!!

108 main secondaries are too small for ANY application. They require atleast 110s, I currently have 112s w K&N pods on mine.

Use sync gauges.

1 adjust valves, COLD engine
2 adjust tensioner, HOT engine
3 after tensioner is adjusted you will check and adjust timing, using a strobe.
4 adjust air/fuel needles, HOT engine...not warm....HOT....the CHOKE is there for a reason, and that is for adjusting Air/fuel mix when engine is cold/warm.



I made this 745B map so you can ensure screw in air correctors are in the proper locations. If you have 754A then the air correctors are pressed in and cant be removed without damage...so dont try.

See the pic below...The part labeled "Bleed Holes" in the pic are where air is introduced into the fuel. The bleed holes allow metered air into the center column/tube where the fuel is. this aerates the fuel, like the one on your kitchen faucet aerates the water....

Aftermarket jets often have bleed holes that are too small, and both stock and aftermarket are prone to clogging, as the whole are pretty small.

When the entrance to atmosphere[heric air on the front of the carb get block, or if the pods mount changes the air flow (more or less), the amount of air changes, and the emulsifier does not aerate the fuel well or properly.


when fuel is entering the throat of the carb from the jet is droplets, rather than spray, it may be an indicator of too small bleed holes, or blocked/clogged holes, or some other issue with the emulsifier. This ca also be to high a fuel level in the bowl.

Carbs are rather simple items that do complicated things. The passages in them are sized for the expected flow of air and fuel. When any of the passages are blocked, or if something causes too much flow, their act is ruined and you get those weird effects.

PS TRek, your pics are very nice, I hope you don't mind, I stole them for future use...

I'm pretty sure the needle holders are factory and I ran wire though the emulsifier holes in them when I rebuilt the carbs so they are clear.

The needles are loose in the slides as they should be.

The diaphragms are less than 6 months old and in good condition.

I'm pretty sure my slide springs are more like 6-7" long (ill measure when they are out again). So I guess that means someone stretched them and there is more slide resistance. This would mean my slides and needles raise slower than they should. Would that cause it to run rich or lean down low? I know the needle will raise slower (fueling less) but will the slide block too much air and therefore cause it to run rich if it stays low longer?

I had the carbs out on friday and raised the float level from 18mm to 19.5mm which makes the right run a little better while letting the clutch out (used to sputter during this time) and then it sputters right after the clutch is all the way out and with a little more throttle it clears and runs good up to about 8k when it starts to lean sputter. Playing with it a little more I found it runs nice if you leave the fuel shut off for a little bit (lowering the bowl levels) but then suffers from lean sputtering above about 6k.

So from this I'm not sure weather it would be better to adjust the floats to maybe 21-22mm and up the jet size to 112ish or try finding a set of springs around 5.25

motormayhem said:

The diaphragms are less than 6 months old and in good condition.


I'm pretty sure my slide springs are more like 6-7" long (ill measure when they are out again). So I guess that means someone stretched them and there is more slide resistance. This would mean my slides and needles raise slower than they should. Would that cause it to run rich or lean down low? I know the needle will raise slower (fueling less) but will the slide block too much air and therefore cause it to run rich if it stays low longer?

I had the carbs out on friday and raised the float level from 18mm to 19.5mm which makes the right run a little better while letting the clutch out (used to sputter during this time) and then it sputters right after the clutch is all the way out and with a little more throttle it clears and runs good up to about 8k when it starts to lean sputter. Playing with it a little more I found it runs nice if you leave the fuel shut off for a little bit (lowering the bowl levels) but then suffers from lean sputtering above about 6k.

So from this I'm not sure weather it would be better to adjust the floats to maybe 21-22mm and up the jet size to 112ish or try finding a set of springs around 5.25

Click to expand...

First off your gonna need proper springs, before moving forward. Stretching the springs may cause a myriad of weird issues & it will never be right, as long as they are employed.

If your new diaphragms came from JBM industries, in my experience I had nothing but issues w them. I have brand new Honda diaphragms installed in my machine now.

The hesitation on takeoff is caused by a lean condition. You need to check the idle and pilot circuits and make sure they are clear. Three tiny holes located under the closed butterflies. Is what feeds the fuel on takeoff. The single larger hole is the idle circuit. located between the butterfly and engine...

I will get pics of these circuits for you cause all newbies have trouble w these...and cant figure out what Im talking about. LOL And Im tired of explaining. ;D

DO NOT RUN THAT ENGINE LEAN.

trek97 said:

First off your gonna need proper springs, before moving forward. Stretching the springs may cause a myriad of weird issues & it will never be right, as long as they are employed.

If your new diaphragms came from JBM industries, in my experience I had nothing but issues w them. I have brand new Honda diaphragms installed in my machine now.

The hesitation on takeoff is caused by a lean condition. You need to check the idle and pilot circuits and make sure they are clear. Three tiny holes located under the closed butterflies. Is what feeds the fuel on takeoff. The single larger hole is the idle circuit. located between the butterfly and engine...

I will get pics of these circuits for you cause all newbies have trouble w these...and cant figure out what Im talking about. LOL And Im tired of explaining. ;D

DO NOT RUN THAT ENGINE LEAN.

Click to expand...

I did clean those before but I forgot about them this last round so I'll check them. They are te jbm diaphrams. I think it is something related to that right carb or cylinder though as I have swapped all the internals between left and rights carbs and the left always runs well and the rights always runs rich (will occasionally flood when float is set to 18mm and the right plug is usually twice as black as the left) compression on both cylinders is about 165ish. When it sat for ~15yrs the right cylinder exhaust valve was open so that cylinder was a little more gummed up than the left but they make similar compression so I would assume that means they are mechanically fine. It's really just 5%-20% throttle where it sputters. It will idle in gear smoothly on both cylinders and accelerate fine just slow starts from a stop while your letting the clutch out and cruising on flat ground are throttle positions that it has issue.

The three holes for the pilot circuit are so small its difficult to get them clean enough. And keep them clean from clogging.



She will stumble on takeoff if they are clogged. They feed fuel from around 1200 to 1800 rpm.

mydlyfkryzis said:

Seems like the right side is coming up later than the left. Is the diaphragm in good shape? Are the left and right springs for the slide the same height? Is the needle "loose" in the slide? it should be wobbly...?
Finally, are the left and right float levels the same? A low float level means a high fuel level, messing up the mixture.

Also, are the valves adjusted well? The fuel spraying back is from the air reversing direction....

The other problem may be the emulsifier holes on the needle jet and possibly main jet....The small holes in the side of the tube are to aerate the fuel and make smaller drops. The drops look big, so I suspect the emulsifier holes are blocked. If you used other than stock brass, I noticed the holes are much smaller in the aftermarket stuff....Large drops of fuel do not combust well...You get less burnt fuel and the larger drops pass though the combustion chamber without burning...They can foul plugs....It creates the odd condition where there is too much fuel, yet you run like it is too lean.

That's about all I got...

Click to expand...

Pressed all the brass out of the carburetor and finally found the problem! It was the emulsifier tube on the primary main. The right side was all gummed up. I didn't realize there were two emulsifier circuits. Still runs a little funky but I'm still working on jetting and understand it will never be perfect without Pj's mods. I also measured the springs and they are about 5.75in so that may not help much.

There should be 5 air holes to check in the primary main jet emulsion/discharge tubes.
Outlet is 1.20mm
The by-pass under throttle plate gradually uncovers more holes as it's opened, from the main pilot discharge to 1 bypass then 2 and 3 come up pretty quick
Most common problem is super rich running when cruising around 4,500 rpm, if all you do is accelerate and keep motor over 6~7K you'll be fine with it as is