20 Most Recent 2003 Yamaha YZ 125 - Page 7 Questions & Answers


Premixed fuel at a 30-1 ratio.

2003 Yamaha YZ... | Answered on May 25, 2015


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.

2003 Yamaha YZ... | Answered on May 25, 2015


The clutch and gearbox share the same oil. The oil for the motor is 10w40. Stick with the major brands; Pennzoil, Quaker State, Mobil, Yamalube or Shell.

2003 Yamaha YZ... | Answered on May 25, 2015


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'

2003 Yamaha YZ... | Answered on Mar 27, 2015


you should try cleaning your carb i dont know how often you clean your air filter but if you havn't done that you should do it also.after you do that turn the gas on lean it over till gas runs out the over flow and give it choke no gas and try kicking it over.you should be able to just loosen up the clamps on each side of the carb and twist it so you can get to the float bowl,unscrew the four screws and blow it out with a air nossle you can try that before you go through the troubles of taking it off to clean it.

2003 Yamaha YZ... | Answered on Jan 19, 2015


check utube for wiring diag.

2003 Yamaha YZ... | Answered on Nov 26, 2014


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.

2003 Yamaha YZ... | Answered on Nov 22, 2014


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.

2003 Yamaha YZ... | Answered on Nov 19, 2014


The only filter in the fuel system is a fine mesh screen in the gas tank - on the end of the pickup tube. Pull the petc0ck and you will see it.

Hope this helped.

2003 Yamaha YZ... | Answered on Aug 20, 2014


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.

2003 Yamaha YZ... | Answered on Jul 11, 2014


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

2003 Yamaha YZ... | Answered on Jun 16, 2014


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

2003 Yamaha YZ... | Answered on Jun 10, 2014


1). Confirm that the transmission is really in nuetral, or insure that the clutch is pulled in.

2). Have you tried removing the spark plug to insure that you do not have a hydraulic lock due to excess fuel in the cylinder? With spark plug removed, any excess fuel should be expelled out the open spark plug hole. CAUTION: INSURE THAT THE SPARK PLUG LEAD IS DISCONNECTED, AND HELD AWAY FROM THE OPEN CYLINDER TO PREVENT ACCIDENTAL IGNITION OF EXCESS FUEL.

2003 Yamaha YZ... | Answered on May 27, 2014


How does the compression feel now that you have it cranking over again. Without the decompression lever pulled in it should be next to impossible to kick it over. also, is there any noise coming from the engine (knocking, etc.) when you got it to start again.

2003 Yamaha YZ... | Answered on May 05, 2014


it will be the coil buddy what you can do is try the coil off the lawnmower on the bike but just to test it as you will lose performance if kept on there

2003 Yamaha YZ... | Answered on Apr 12, 2014


It would appear that the float is not shutting off fuel flow when the bowl is full--take off the bowl, remove the float and needle valve. Turn on the fuel for a moment to wash out the needle seat, clean the needle tip and reinstall the parts you took off. If the float is brass, shake it to listen for fuel inside the float. If there is, replace it. Plastic floats don't have this problem. Hope this helps!

2003 Yamaha YZ... | Answered on Mar 26, 2014


this happened with my sons pw50 where the piston ring had snapped and when it locked it was stuck bewteen the piston & bore

i would seek a shop or mechaninc to look at the top end and isnpect the piston & rings for wear or damage

dont keep kicking as this could result in further damage

2003 Yamaha YZ... | Answered on Mar 20, 2014


sounds to me as if your carb is all gunked up pull it off and clean it then see what happens

2003 Yamaha YZ... | Answered on Feb 02, 2014

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