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I bought a used 2001 Yamaha big bear 400 the bike had set up for a while with gas in the oil from a stuck float in the carb. I rebuilt the carb changed the oil and adjusted the valves. Checked the timing tensionier which is still along way from bottomed out. With that all said the bike runs like a top until it gets warm then gets a outlet clatter about mid throttle when in neutral or in gear goes away when you get higher rpms . Could it be a cam chain guide worn?

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  • Motorcycles Master
  • 767 Answers

It seems the float level is not correct in the carburator float chamber, recheck and reset and also recheck the valve clearance and check the spark pulg gaps and also reset the air fuel mixture ratio.
when all the engine to its normal temperature and than adjust the air fuel mixture screw...take it in slowly to the end taking care not to tight it toomuch to avoid damaging the tip of the screw and than go anti clock wise two and half turns to will feel the engine running smoothly plus it or minus the air fuel mixture screw at this point to suit it.
Hope this helps!

Posted on Oct 06, 2013


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Posted on Jan 02, 2017


Z Laws

  • 375 Answers

SOURCE: I need tuning specs for my 1982 suzuki gs 750.

You need to fix the fueling first - without fuel it won't run!
Your other problem sounds like an air leak - either the manifold or the carb. Check by spraying WD-40 or CRC at the manifold and carb join while the bike is running - if the revs change (either up or down) you have a leak.

Posted on Jun 29, 2009

SOURCE: I bought a 1985 GS 550 LF. It had been sitting

Gas pouring out of the carbs means the float pin are not sealing in thus the over flow.
Go a little down thn .77in , best would be to bench set them.
Take a pipe say from the tank to the feed pipe of the carbs (best would be to remove the tank and place it higher on your work bench to get the gravity flow to the feed pipe of the carbs)
Allow the flow to the carbs and monitor the over flow, see which carbs over flow, remove the float bowl and reset the float and let it go a little less thn .77in, refit the bowl and retry the feed in and will come to a point where gas wont over flow, open the bowl and see the level of the gas , it should be covering the jets, but remember that since you will have the float bowl out the gas will show low as when its submersed, the jet stem in the float bowl pushes the gas level up so dont get mixed up when you see the level low , i am sure you will be able to judge it for yourself.
I had the same problem in myYamaha(seca) XJ750R !981and finally managed to win over the problem going over it the way I explained.
Hope this helps! Good luck.

Posted on Jul 14, 2009


  • 2 Answers

SOURCE: Rpms speed up faster then bike does. Sounds like clutch slip.

You can adjust it by slackening the cable...unless it has hydraulic operation....Otherwise get it replaced before you do more clutch dust and debris in the oil, so dont forget the oil and filter change too.

Posted on Jul 22, 2009

cracklin joe

  • 105 Answers

SOURCE: 2002 Big Bear 400. Dies after a few seconds upon startup

sounds to me the valves are not properly adjusted, their to tight,...i had run into this in a japanese car once,...check it out and let me know,.....cracklin joe

Posted on Jan 10, 2010



  • 267 Answers

SOURCE: floats not set

Float tabs come set flat to surrounding plate, bend up to decrease level and down to raise level. Raised level too much and you risk fuel overflow on sustained inclines and too low a level and you will lean out at high revs and damage valves/piston real quick. There is no set level to speak of, but better to err on the side of losing a bit of overflow. The overflow drains from the carby via a plastic hose from just above float bowl flange.

Posted on May 08, 2010

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