Question about 1986 Yamaha FZ 750 FM (Japan)

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1983 FZ 750 high idle

I have a 1983 YZ 750 yamaha. When I start it, it races about 4000 rpms. If I screw the jets all the way in, it brings the revs down. I was told that I might have a vacuum leak. If so, where should I ;look?

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Hi, Stevemagney and the usual suspects are:
1. Throttle cables improperly adjusted, pinched or need lubrication.
2. Idle adjusting screw needs to be backed off.
4. Air fuel mixture adjusted too lean start with 2 full turns.
5. Intake system air leak.
6. Fast idle choke ramp is not releasing.
7. Broken throttle return spring.
8. Damaged diaphragm or slide.
9. Faulty MAP, TPS, ATS, O2, sensors or wiring/connector
10. Multi carburetors not in sync.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links blue below. Good luck and have a wonderful day.
FZ750 Super High Idle Problem
carb high idle problem
1985 1988 YAMAHA Genesis FZ750 Service Manual Repair Manuals AND Owners... $10 cheap
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-fz-owners-manuals

Posted on May 24, 2017

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SOURCE: I have a 95 yz 125 head and 98 yz 125 bottom end.

You have a 50/50 chance that they will work okay. All the mounting holes need to line up and the cooling holes as well. Get a head gasket for the '98 and see if all lines up. Will the exhaust pipe fit the '95?

Posted on Apr 30, 2009

  • 132 Answers

SOURCE: changing carb jets

the main jets just unscrew out use a socket if you can but dont over tighten when refitting.undo the 4 screws holding the carb bowl on and the jets are straight in view.

Posted on May 28, 2009

polarcycle
  • 1392 Answers

SOURCE: yzf 750 wont rev past 4000 rpm

Sounds like you need some plugs and the carbs cleaned and synchronized.

Posted on Jun 10, 2009

  • 3567 Answers

SOURCE: yamaha yz 125 1994

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Can I get a “very helpful” rating on this answer? Thanks!

Posted on Jul 06, 2009

  • 1 Answer

SOURCE: 1983 suzuki gs 750 New airpods and jets. Bike not running right

You are dealing with Suzuki vacuum carbs, you cannot just replace the air box and re-jet. What you are running into is there is no pressure to raise the diaphragm because there is no restriction to create such vacuum. Either put the stock box back on or go to the biggest main jets you can buy. Sometime even when you get stage 3 jets you still have issues. Vacuum carbs are not made to run with no restrictions.....putting aftermarket exhaust on it will make things much worse.

Posted on Sep 30, 2009

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5. Intake system air leak.
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1 Answer

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1 Answer

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It sounds like the idle screw is not set right., but if your going to clean the carbs anywyas. Clean them, sync them and see how she runs, if still doing the same thing the idle screw needs to be adjusted. The RPMs should be between 800 to 1200 while idling. If your bike is an older on it will most likely sit around the 1200 rpm at idle.

Nov 10, 2008 | 1986 Yamaha FZ 750 FM (Japan)

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