2003 Yamaha YZ 125 - Answered Questions & Fixed issues

you need to clean or replace the float valve in the carburator.

Hi,there is no adjustment from inside the clutch caseing,you can only replace the clutch plates and springs,all other adjustments are done by the cable.

Every motor is having fuel filters filtering in 3 steps an tankfilter, fuel tap filter and a filter inside the carburetor. but a separate fuel filter can be there reading this but its not neccesary by the 3 filter steps on every fuel engine a good airfilter is having more priority. inline fuel filter Yamaha 2 Stroke

excessive piston clearance.really needed bore job with oversized piston,not just honed and rings.measure piston to cylinder clearance,check spcifications and verify

Premixed fuel at a 30-1 ratio.

No oil goes into the crank case as it is a 2 stroke. The oil is premixed in the fuel at a 30-1 ratio. The gear box takes 10w-30 se oil.

look on the engine, there will be marking on it for the 'cc' if a yz80 it will prob be '79cc' and if yz85 it will prob be '84cc'

check utube for wiring diag.

If it does stay in gear when barely throttled but does not stay in while under load, the engagement dogs on the gears(inside the engine) are bad and the engine will need to come apart to repair it.

wear or play on the gear selector drum,could even be the gear selector plate on the end of the drum is loose its star shaped with a central bolt or screw,check the locator spring also.

Service manual says oil capacity is 19.4 oz. per leg which is 573.726 ml per leg. Be sure that you have drained all the old fork oil out first.

hi there it sounds like the return spring is broken inside the cases this useally a sidecover off to replace it hopes this helps

it should be just a bolt that goes through the base of kickstarter then wedge a screw driver into the slot to widen it and it should come off .but if you want to remove the shaft and all you will need to split the cases hope this helps

Smaller pilot jet