Topic: 1972 cb 350 four carb problems

[xbustion]

I just received a 350 four from my friend to give him a hand rebuilding the carbs. I have bought 4 rebuild kits for them cleaned out all the carb mainbodies with compressed air wire brush and carb cleaner. I have also put all new rebuild parts in it and have put the carbs back on the bike i got all the slides at the same height but the problem i have now is when it idles the carbs will caugh and it isnt 1 carb it usually alternates. I run it for a little while and it keeps caughing and finally it will caugh it self dead. I was thinking it might be my needles adjustments for the slides.Any sudgestions.

[eldar]

You need to look at the plugs and see how they look. We can then tell if they are sooty or too lean. Normally with the coughing, rich is the cause. How old are these plugs?
Have you adjusted the valves, set points and timed? How old are the points or is it electronic?

If you have covered all these areas, we can then work better to diagnose the carbs.

[xbustion]

I was trying to adjust the carbs for awhile so the plugs were sooty but i wire wheeled them off and checked for clearance and put them back in but the same problem has occured. Although i could definately check for valve clearance i dont know what spec is for this engine. Also i do believe the ingnition is electronic it has 2 coils branching to 4 spark plugs.

[eldar]

You will want to double check ignition to see if it electronic and for timing anyways, just to make sure.

The valve clearance should .05mm or .002in on both intake and exhaust.

Also you should check the cam chain if the bike has one. On this site is info about adjustments and maybe even a pdf format manual you can download.

Also your air screw, which should be on the air filter side of the carbs, should be .75 turns out according to specs on this site. I will see if I can find a link to the manual.

[xbustion]

Thanks alot i  have the day off so i might be posting quite a bit on here. I have been working on these carbs for 2 weeks now and i think i am very close to getting this problem buttoned up. I appreciate the help.

[eldar]

Here is the link that should get you to a bit more info.

sohc4.us/node/10   it does work. There is limited info and there has been a problem with the upload for the manuals. Someone else may have a manual. Do a separate post for one and see if anyone has one.

[Gordon]

Try this:

Clean out the stock slow and main jets and put them back in instead of the ones that came with the kits. 

[xbustion]

I just relashed the valves and now the 1 and 3rd cyclenders are doing it only. I dont know if i am on to somthing with the lashing.

[xbustion]

Does anyone know what level to set the needles in the slides in the carbs. I have mine set at the second from the bottom maybe thats why my spark plugs are so black.

[eldar]

There is not a whole lot on the 350/4 for settings right now. But this is how it works. Your needles have clip positions. The higher the clip, the lower the needle goes into the jet and the less fuel you get meaning you will run leaner. At least that is how the 750s work with clip positions. Yours should be similar though.

Also, Too Tired has ajet chart the shows whn certain jets get used.

BUT if you idle and your plugs foul up, then you are running TOO rich in the LOW speed jet area. Here is where the idle screw comes in.

Again your bike might be different BUT generally if the screw is on the AIR filter side, then turning it OUT will make the mix leaner and in makes it richer. SO you would want to go OUT.
Now if it is on the engine side of the carb, OUT makes is RICHER and vice versa.

So you need to clean the plugs good and idle for a while and then pull them and see what they look like.

This will let you know how your idle circuit is.

Clean them good again and try to run at a higher rpm, above 4000 rpm, and then kill the bike WITHOUT lertting it drop back to idle.
Pull them again and see what they look like. This will give you an indication of you main jet settings.

Again, you should set you floats to the proper height. I dont know what that might be but someone else whould. Start a post about the float height and you should get a bite.