Question about 2003 Yamaha YZ 125

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Yamaha yz 125 1994 what are the carbs original jet sizes(pilot and main)on mikuni carb

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  • Jo Harvey
    Jo Harvey Aug 07, 2013

    most helpful answer i've been able to get



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Posted on Jul 06, 2009


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How are the basic setting in the carburator?

You have a mikuni carb. there are curcuits to the carb. the first that works from idle to 1/4 throttle is the pilot cicuit, from there you transition to the needle jet/and jet needle. That controls the 1/4 to 3/4 throttle and then the main' jet which controls WOT. you may have a air screw that would be before the throttle plate if it is after it is a fuel screw find the factory specs for the jet sizes and make sure all is correct. if not you isolate where the problem is and correct in a rich or lean adjustment' I race yamaha 2 stroke road racing bikes, it is not an easy task sorry to complicate you so much

Sep 28, 2010 | 2003 Yamaha YZ 125

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Site above has all the parts and specs for your bike. Jet ranges are large for a YZ as many mod's are available and riding conditions contribute largely to a peaky 2 banger. Start with #40 pilot, and #420 main. Trial and error from there. Cheers.

Apr 26, 2010 | 2003 Yamaha YZ 125

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What should the stock carb jets be for a 94 yz250 with the stock pipe and aftermarket silencer

Stock Jetting for a 1994YZ250 is:

350 main
45 pilot
J8-6EJ33-61 needle

Adjust your jetting down one size for each 1000' of elevation above sea level. Needle clip position on the needle fine tunes the pilot circuit.


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1986 yamaha tt225 I need carb specs please

Not sure exactly what you are needing? Carb size? Jet sizes?Float adj? Also ,is this an '86 TT225S? If so the carb is a 40mm Mikuni, the Pilot/Slow Jet is a #42, the Main jet is a #118 Can you be more specific on model and what you are looking for if this is not what you need?

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1 Answer

What is a good carb set up on a 2005 yz125 with new motor hot rod crank and wiesco piston all stock specs. I have a 45 pilot jet now with std main jet. Took out the 40 pilot jet because of breaking up at...

this will depend on what gas oil mixture you have

check this topic out.



Jul 08, 2009 | 2004 Yamaha YZ 125

2 Answers

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sounds like the main jets are partly pluged, you must remve all brass jets and seats including needle jet and its slide soak in carb cleaner and blow out with compressed air only.. hold up to bright light to verify if all are clean. jim

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