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Discussion Starter · #1 ·
Hello world,

Novice mechanic here.

I recently bought a '69 CB 350 used, beautiful bike (my first bike!). I am having trouble keeping it idle. On a fully charged battery, the electric start works completely fine and runs when I hold the throttle open. As soon as I let go of the throttle, it dies and does not idle.

I've adjusted the idle screws and air/fuel mixture screws a number of times and have currently set them to what I found to be factory. (Idle: 7/8th outward from fully screwed in, air/fuel mixture screw: 1.5 out from fully screwed in).

Some things about it:
-the more times I try to start the bike after it fails to idle, the harder it gets to start until it finally doesn't start.
-the right cylinder seems to be failing to fire. the right side exhaust doesn't get warm. A few days ago when I tried, it finally did get hot after multiple starts but today, after starting from cold it is not getting warm at all.
-I've cleaned the spark plugs with a sponge because they did feel a tad bit moist when I pulled them out and were a kinda black
-the previous owner did a thorough carb clean right before the bike was purchased and insists that's not an issue here.
-if I go for a quick spin, I can get into second but then when I shift down into first it dies.


Any advice would be much appreciated! Thank you
 

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If you have dark plugs, you are too rich. I think one of your float bowls is getting jammed which is why only one side is firing. I would replace plugs too. They are cheap and it that is a problem, then it is not a possibility. Also check the wires. I have had a burned up wire before.

Check this out

 

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The motor runs off the battery. all the stator does is charge the battery. The more you try to start it with the starter the less elec you have for the motor to run . IMHO the problem is in the carbs Wet and black plugs show a rich condition. Fully charged battery and good spark I would take the carbs back down and clean the idle circuits again.
Just my thoughts .

Bill H
 

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Discussion Starter · #4 ·
If you have dark plugs, you are too rich. I think one of your float bowls is getting jammed which is why only one side is firing. I would replace plugs too. They are cheap and it that is a problem, then it is not a possibility. Also check the wires. I have had a burned up wire before.

Check this out

Thank you for the link!
So I got new spark plugs today and replaced both and still no luck. The right cylinder does not seem to be firing and I can't get it to idle. Do you know what the best way to fix a sticking float bowl would be? I haven't seen any gas leaking out of the carb so I'm not sure if this is the issue
 

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Discussion Starter · #5 ·
The motor runs off the battery. all the stator does is charge the battery. The more you try to start it with the starter the less elec you have for the motor to run . IMHO the problem is in the carbs Wet and black plugs show a rich condition. Fully charged battery and good spark I would take the carbs back down and clean the idle circuits again.
Just my thoughts .

Bill H
So I replaced the spark plugs today and tried on a full battery again. No luck getting one of the cylinders to fire and then keeping the bike in idle. In a hypothetical scenario if the carbs are in tip-top shape, both cylinders are firing, and you start on a full battery cold would the bike need time to warm up before it would idle? Or it should be able to just turn on and then idle right away without the need to open the throttle?
 

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If I were you, i would pull off the top of the carbs if you can. You can then see what the float bowls are doing. I read in another thread though of a similar problem. His solution was replacing an engine coil.
 

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See if there is anything familiar

 

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Your bike has the duel points Some times this can cause problems. Do you have a FSM ? Go back thru and reset the points and timing. Compression check ? Go to the local auto store and buy a spark tester. About $15.00. It plugs in between the coil and plug and has a light that comes on when the spark fires .That way you can see if the plug is firing. I am still leaning towards the carb rebuild.
The bike should start up and idle hot or cold. On the choke plates there are ,for wont of a better word, little trap doors that have springs on them . When starting a cold motor ,choke on full the springs control the amount of air flow thru the closed choke for the correct mixture. Check the points and timing ,use the spark tester and also check compression. Still having problems ? tear the carbs back down. Just my 2 cents worth.

Bill H
 
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