Motorcycle Repair: bike cutting out, diaphrams, plug cap

Question
QUESTION: I bought a 1980 cx500c only has 9800 miles on it. Had to put a tank on it from an 81 and used the coil mounts as well. Had the carbs cleaned and put new plugs in. have adjusted the carbs going down the road. New o rings put in going from the carbs to the jugs. The bike cuts out or skips from low to high. still gets 50 miles a gal. If you let off of it you will hear it pop or puff a few times out the pipes. I also put an inline fuel filter for a cycle on it. I take the fuel cap off and don't hear a vacume sound. If I can think of anthing else I'll let you know. Just trying to get the bugs out.

ANSWER: More than likely the air shutoff diaphragms have holes in them.  They shut off the fuel to the low speed circuit when you let up on the throttle so the exhaust doesn't load up with unburned fuel.  When they get holes in them, the bike will backfire and pop like crazy when you let up in the throttle.  

Regards,
Rich

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QUESTION: that would explain the popping. How about skip or not running smooth at any speed. It isn't real bad but I know or think it should be better. If you run any gear up close to shifting to the next and hold it there I feal the roughness. Today I left work and ran ten miles and came to a stop light and it just cut off. Started back up right away. Would all this be from the diaphrams? Oh, I pulled the plugs last night and they were looked great. Would the valves need adjusting?   thanks for your time.

ANSWER: No, the backfiring is the diaphragms.  When it runs rough, apply a little choke.  If it smoothes out, you still have a lean carburator and you may not have the carbs completely clean or the float level is not correct.  If it doesn't smooth out, it's probably an ignition problem with a bad coil, plug, plug cap or plug wire.

Good luck
Rich

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QUESTION: Hi Rich,
  I've been working on this bike when I have a lil time. ok   well I can pull the left plug wire off and the motor has no affect. I can turn the left jet all the way in and the motor doesn't change at all. I pull the right plug wire off and the motor will shut down. To keep running I have to give it some throttle to feed gas through the left carb. If I turn the right jet in the bike will shut down. I know the gas is getting to the left side but it will not cooperate. I took the carbs off again saturday and made sure that all passage ways were clean. Now. Both carbs have a air vacuumed diaphragm to keep it from popping but the left side is the only side that has a accelerator pump. would the diaphragm on the pump cause all this to happen if it were bad? I didn't see any holes but not saying one wasn't there. Pulling the choke out did help but I can't seem to pin point the problem.

Answer
Carl, it sounds like the left carb is still running lean.  Have you manually sync'ed the carbs?  I can't remember for sure any more but I think you have to adjust the carb cable lengths to make the throttles open at the same time.  If the right carb has more throttle at idle, the bike will act the same as you describe.  The fact that the bike runs better with choke indicates it's running lean. I'm guessing it's the float level that's not quite correct making the left carb lean out.  The missing you feel is probably a lean miss.

The accelerator pump only works on throttle tip in and if it's misadjusted or bad the bike will hesitate as you roll the throttle on.  I don't think that the problem you're describing.

Regards
Rich