Hinson Clutch and backfiring

2 replies to this topic
  • onebadyz450

Posted December 26, 2004 - 04:51 PM


I just installed a hinson clutch basket and rebuilt my top end. After putting the basket in I notice a funny noise when the clutch lever is out. I pull the lever and it stops. Is this normal or do I have a bearing or something going out. Plus after I redid the top end the bike has started to backfire I adjusted the fuel screw and it is not as bad. Do I need to fine tune the fuel screw or is the timing off? I dont think it the timing because it still runs, but I am not 100% sure. Please help me if you can.

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  • RCannon

Posted December 26, 2004 - 05:12 PM


Mine did the same thing when it was brand new. The noise went away after a few rides and the engine returned to its normal sound.

I wondered if the tolerance on the clutch hub bearing was different. I changed the bearing but it made little to no difference.

  • grayracer513

Posted December 26, 2004 - 06:32 PM


Most 4-stroke singles will make a growling, rattling sort of noise with the engine idling in neutral. That's because the engine doesn't really spin at a steady speed, but accelerates on each power stroke, and then suddenly decelerates at the next compression stroke. This gets transmitted to the transmission via the clutch and the whole thing rattles and grumbles. Normal. If it will go away when you speed up the engine or pull in the clutch, there's no problem.

There are two common causes of exhaust decel backfire. One is lean idle mixture. If this is the culprit, you should be able to clear it up by backing out the fuel screw 1/4 turn. Don't adjust idle to the point where the engine runs wrong just to clear up a little popping noise.

For more info: http://www.thumperfa.../jetting.htm#PJ

Cause number two is an air leak at the mid-pipe joint or the header/head joint, or elsewhere in the exhaust. Tighten the clamp if there is one, and check the joint at the head. Don't worry too much about it, though. If there doesn't seem to be a fire hazard, and it isn't so bad that you think it will blow your muffler off, it won't hurt anything.

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