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Discussion Starter · #1 ·
74 CB360. Left side pops back into carb, hard, often until it warms up. Choke position does not seem to make any difference. I did set the timing with a strobe, checked the valve adjustments, cleaned the carbs very thoroughly and set the pilot jet screws best I can. When it is warmed up it does not pop like this, but cold it would blow the carb right off the rubber manifold if it could. So, what am I missing?

Bob
 

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Usually this scenario is caused by retarded ignition, but you strobed the timing yes? Are the plug readings uniform?
 

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If it is backfiring through the intake it would be a timing issue. I have had a case where the timing was right on the carbs were good and still would pop the carb off. It ended up being a bad exhaust lobe on the cam shaft. It had worn down so for that it was not opening on the exhaust stroke. So as soon as the intake valve would open the exhaust would blow out the carb. A new cam shaft fixed it. I also had problems with my 360. When reinstalling the head on the engine I had the cam put in 180* wrong. I took off the cam sprocket and rotated the cam 180*. That fixed the problems too. This is just what I have found. Maybe just something to look at.
 

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Discussion Starter · #5 ·
Thanks for the clues. I'll try checking the valve clearances and the timing again. Do you think this would explain the popping when it is cold, but not when warm?

I thought about the cam being 180 off, but I don't understand how that could matter. The PO had replaced the advance mechanism and never got it to start (so he sold it to me), but I did by removing the timing cam and replacing it 180 degrees around on the advance.
 

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Were the springs good?
 

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Discussion Starter · #7 ·
I think so. The timing looked good with a strobe light, and advanced smoothly to the proper mark.

Since it only pops back into the left carb,, I would think the advance works, because if it was faulty wouldn't both sides be bad?
 

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For sure...I was just checkin :) My XS650 has trained me to be vigilant of a properly sorted advance unit... :roll:
 

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I could not get my 360 to run right. So I was checking everything. The only thing that I could find was a bad regulator. I pulled the spark plugs to make it a little easier to check the timing for the 10th time. That is when I noticed the intake valve was opening as the piston was coming up. And the exhaust valve would open as the piston was going down. The right had cylinder was right though. To make a long story short, that is why I rotated my cam 180*. I do not know why the right side did not change to, but both sides are working the way they should. I don't know how I did that to begin with but I did. Good luck.
 

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Discussion Starter · #10 ·
Just to put an end to this thread, the popping stopped. You never know what the magic was, but a combination of premium gas and leaving the choke on far longer than I thought I should seems to do the trick. After it is warmed up I can open the choke completely, no problem.

Thanks for your ideas.

Now I'm trying to figure out why the starter clutch works at all. I cleaned it all up, and it does work, but I just can not understand the physics of it.
 

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The rollers wedge in the oval slots in one direction, roll to the large side where they can spin free in the other direction.....
 
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