CB360 Running rough

Hey guys,

I just picked up a cb360 a few weeks ago. Bike would only run one one cylinder when I got it. I though it was timing so I checked the points and the timing was advanced a slight bit from where it was supposed to be. I set the timing back a little bit so that the timing light would come on when the stationary timing mark lined up with the fire ("F") mark on the alternator cover. Still would only run one one cylinder. Traced it back to that one cyclinder wasn't receiving any fuel. Took the carbs off, cleaned the gunked up float valve so that the bad carb could receive fuel again. Cleaned the fuel tank, derusted the tank, inline fuel filters. Bike fires right up now, but I went to take it for a little test ride yesterday and the bike is very surgy when accelerating. Accelerates fine up to about 3500-4000 rpm, then lags and wont accelerate further until I give it more throttle at which point it jumps and accelerates like a bat outta hell. My two thoughts at this point are:

1) I need to advance the timing back to where it was (which would be ahead of the fire mark)
2) Carbs are not mixed properly, synched properly, cleaned all the way, etc. ( I did do a bench synch and thought I cleaned them fairly well with the spray can carb cleaner, I have not touched the air screw or anything at this point, just adjusted the idle sped to about 1300.)

The one thing that makes me think its a carb problem is that it seems to run much better with the choke on and seems to accelerate like it should. Any thoughts or help would be appreciated.

Nick

Do you have pods fitted?
I make vacuum adapters for 360's, PM if you want a pair

^ what he said. Sounds like the typical cb360 with pods issue.

Stock airboxes and stock exhaust. When I got home today I decided to check the mixture screws. The right mixture screw was at 1.5 turns out, the left was .75 turns out, so i backed the left out to 1.5 turns out as well. It ran a little bit better today, it was less jerky and violent when accelerating but still very far from a smooth acceleration. It starts up and idles nicely at 1300 rpm, but when I make a pull to try to further diagnose, I come to a stop afterwards and it wants to idle around 3000 rpm with a slight pop and putter from the left exhaust (It will continue to idle that high and the idle won't drop unless i slightly turn the idle speed screw, and then it will drop back down.) When I pull the plugs the right is a gray color and the left side is more dark brown/black.

It has the correct compression in both cylinders, and I set the timing back to how I did it the first time (according to the manual where the timing light lights up on the F mark.) I'm not the most seasoned bike mechanic, so all help is appreciated.

nnichols211 said:

Stock airboxes and stock exhaust. When I got home today I decided to check the mixture screws. The right mixture screw was at 1.5 turns out, the left was .75 turns out, so i backed the left out to 1.5 turns out as well. It ran a little bit better today, it was less jerky and violent when accelerating but still very far from a smooth acceleration. It starts up and idles nicely at 1300 rpm, but when I make a pull to try to further diagnose, I come to a stop afterwards and it wants to idle around 3000 rpm with a slight pop and putter from the left exhaust (It will continue to idle that high and the idle won't drop unless i slightly turn the idle speed screw, and then it will drop back down.) When I pull the plugs the right is a gray color and the left side is more dark brown/black.

It has the correct compression in both cylinders, and I set the timing back to how I did it the first time (according to the manual where the timing light lights up on the F mark.) I'm not the most seasoned bike mechanic, so all help is appreciated.

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I would make sure that you have no tears in the diaphragms (even tiny ones), sounds like its a jerky from overly lean mixtures every so often when you open the throttle.. the needle is probably not lifting to let enough fuel in. Just fixed this on my friends bike, we put replacement JBM industries in $20 each, accelerated great after that. Also i would make sure you have enough slack on the throttle cable on the lock nut up top near the handlebar

Do this...

http://www.dotheton.com/forum/index.php?topic=63133.0

Awesome write up, I'm going to go through the carbs once again today. Is there any other mixture screws on these carbs or is it just the idle mixture screw?

I'll post my results afterwards. I have an emgo carb syncher that I just bought (the one with 4 vacuum gauges). Looks like I will need an adapter to use it with these carbs, does anyone know someone or a website that sells these?

nnichols211 said:

Awesome write up, I'm going to go through the carbs once again today. Is there any other mixture screws on these carbs or is it just the idle mixture screw?

I'll post my results afterwards. I have an emgo carb syncher that I just bought (the one with 4 vacuum gauges). Looks like I will need an adapter to use it with these carbs, does anyone know someone or a website that sells these?

Click to expand...

You have to buy them from CrazyPJ. He's the only person that makes them. PM him and he'll send you two.

nnichols211 said:

Awesome write up, I'm going to go through the carbs once again today. Is there any other mixture screws on these carbs or is it just the idle mixture screw?

Click to expand...

Thanks, I know its long. But, probably worth reading if your new or unfamiliar w Keihins they used on 360s

The A/F mix needle ( screws ) are the only adjustment, unless some smart ass wants to pipe up that the sync is adjustable too.

Park bike level on center stand for a/f adj. and its important to have her fully warmed up to operating temp. Cold engine will cause the atomized fuel to re-condense to a liquid state. The hot engine helps to keep the atomized fuel...atomized. If you adj a/f mix cold it will change as the engine warms and need readjusting. Thats the reason they install a choke on it. The choke IS the adjustment for starting and running the engine when its cold and the atomized fuel is condensing.
So warm bike, adj idle speed to 1200, then adj a/f mix on left carb to fastest idle, re-adj idle speed back to 1200, then adj right carb a/f mix to fastest idle. then adj idle speed to 1200, repeat...go through them twice to to be sure you got it good as you can. Mine is happiest at 12.8 to 1 a/f ratio.

If you listen real close. you may notice the rpms vary slightly and rythmically during this process. That is actually caused by the fuel level in the bowls dropping and raising w the floats opening and closing feeding fuel. And they get a little lean and richen back up as they fill.

and remember it may just take a tweek on them the second round like 1/16th of a turn.
Also, the reason they made these easily adjustable to start with is, the mix will change w outside air temp. and altitude. So, if you set em up in the spring when its 50 degrees it will need re-adjusting when its 90 degrees.

I wanted to post a quick update so far. I took the carbs off and cleaned them again and noticed the primary jet on the left side was slightly clogged (the same side that wouldn't originally run due to a clogged float valve.) Put it a new jet and it ran so much smoother. No more jerky acceleration, and has good throttle response.

Sometimes when stopping the idle will tend to linger around 2000 rpm, but I will properly adjust the idle speed tonight with the engine warm and post results.

Thanks for all the help so far.

good ;D

It been running really well lately but still fighting that high idle. I will ride it for a bit, come to a stop and the idle will hang around 2000-2500 rpm and it will take almost a minute for it to go down to the 1200 that I have it set at. Or if its lingering around 2500 at idle, I will give it more throttle and sometimes it will come right now to 1200.

I left some play in the throttle cable so the throttle cable isn't causing the high idle. If i play with the idle mixture screw, I can't notice any increase or decrease in engine speed when I turn the screw in or out. Does turning the screw in make it richer and out make it leaner? Could this idle problem be caused by the carbs not synched?

More likely an air leak somewhere around your carb/intake boots

Okay I'll check that out now

If it is an air leak, it's probably slight. Try spraying WD40 or starter fluid around the boots. If revs increase, you found yer leak

nnichols211 said:

If i play with the idle mixture screw, I can't notice any increase or decrease in engine speed when I turn the screw in or out. Does turning the screw in make it richer and out make it leaner? Could this idle problem be caused by the carbs not synched?

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GRRRRRRR WTF !?!?!?

OK time for some tough love.
YOU seem to be confused w what you are doing! I will post a pic.

EACH CARB has it own a/f mix adjuster needle (screw) AND once you got them set for the fastest idle speed... DO NOT FUCK W THOSE AGAIN.

The IDLE SPEED ADJUSTMENT is a very large knob type screw ON THE LEFT CARB ONLY !!!

I AM GETTING THE FUCKING CAMERA...BRB!!!

If your throttle snaps back nice. AND you got a little play in the throttle (a little slack in the cable end that hooks to the carb linkage. AND the linkage is working smoothly and seating fully on its stop.

Then a hanging idle speed of 2k can only be 2 things. OR could also be a sticky advancer I suppose

Either you got an air leak (someplace) boots, carbs, whatever.
OR
The throttle plates (butterflies) inside the carbs are binding up and not getting fully closed when throttle is released. These need to be centered on the shafts. so they dont scrub the walls of the carbs and hang open. It dont take much.

But the engine IS getting air from someplace.

and yes,
if they are not synced. One carb will be feeding more air and fuel to its cylinder than the other. that cylinder will want to idle faster than the other.

at the slower 1200 rpm it will make it run weird. the one will be wanting to run stronger, pulling the weaker one, the weaker one will be trying to pull the stronger one back. so to speak sorta in a round-a-bout way.

Here is the pic. I hope this helps. sorry bout the whole tough love thing...sometimes it gets frustrating for me to try and help without the bike sitting here in front of me.

and sometimes you kids drive me insane! ;D

So, set idle rpm adj for 1200.

then start w a/f mix needles till it idles fastest.

then reset idle rpm adj back to 1200 if necessary.

Unless there is a big swing in outside air temps or you ride up a to the top of a mountain.
then dont fuck w the a/f mix again.

You can fuck w the idle rpm adjuster all you want, as long as you set it back to 1200 every time.