YZ 250 throttle problem

[Orangeman64]

I need a little help from the experts out there. I went riding at a local MX track yesterday and had some wierd happenings with my 2000 YZ 250. On 3 seperate occasions yesterday my bike just accelerated out of no where. It was like over revving. It happened 3 seperate times and always just before going up a jump. On the last one I guess I paniced and grabbed the clutch and front brake but was carrying so much speed still flew up the face of the jump and as you can imagine did a serious nose dove on the landing, well it didnt go all the way over but my lower half slammed the handle bars real hard and sprained my shoulder also. It felt like a heart attack my heart was beating so hard. Nothing as scary I guess as hitting a jump a lot faster than you can handle and with no control over it. Any ideas on what could be making my bike over rev like this would be greatly appreciated before I end up taking it to my local shop and spending all that money, especially if its an easy fix. I did take the throttle assembly apart and clean the upper cable but still had the problem. Thanks, I'm not riding it again until I can figure this problem out. Too dangerous.

 

[wornknobby]

take apart your throttle housong and check the condition of your cable. it may be frayed or even dry :ohmy:
if so just lift the cable high enough so you can spray lube into the cable sleeve and it will run down to the bottom where it meets that monster carb. :)

 

[spridget]

I had a thing like this wen i was 12 in 1983 with a 125 rm.

Reel scary , i was in control but when this happened i did not liked it anymore. So we took the bike to the dealer but they could not find anything. The mechanic drove it in al 6 gears on the street without helmet and me hoping it would get stuck.. nothing.
So me driving it on the mx track and yes the throttle would stick again.

Problem was some sand in the carb. Grrrr

 

[rickyd]

Check for an air leak of some sort.. Check the reed cage gaskets, make sure the carb is seated correctly in the boot..
Hope this helps you out,
Rick

 

[Solid State]

Couple of things. If it surges with no throttle then it is most likely an air leak. I have found the ignition side crank seal to cause this same problem in the past. If your seals are 5 years old, you should replace them.

If it revs like that when you apply throttle, but does not come back down, then be aware that there was a recall on the plastic wheel in the throttle assembly (at least for the '01 model). The cable gets caught between the plastic wheel and the throttle housing and results in a very dangerous stuck throttle condition. I got the recall notice, went to the dealer to get the replacement wheel and he told me that I had to bring the whole bike and have him replace it!! I wound up getting a Motion Pro unit instead.

Whatever the cause, DO NOT ride this bike without fixing this condition.

Hope this helps.

 

[Highflier]

YZ throttles were bad up to '04 if you ask me. Spend $30 and buy the Motion Pro unit.

 

[jmics19067]

the pulley recall started in 96 I think... the reason why the dealer wanted it back is to stamp the frame and to get the VIN back to yamaha to show & document the recall was done.