my 2000 yamaha yz125

[reeseyz125]

i have a 2000 yz 125 and im having problems with it. it will run good for like 45 mins. before it will shut down on me. i put a new air filter, jets, and spark plug. but basically i ended up rebuilding the carb. can someone please help me and let me know if im missing something here. im running my gas at 32:1 and checking my plug after each ride and nothing seems to be wrong but it shutting down on me.


thanks.

[MXtras]

When you say it shuts down - will it re-start right away or do you have to let it cool down first?

When it shuts down are you able to spin the motor over or does it sieze?

First guess (assuming all is well with piston/cylinder) would be that the coil or CDI is overheating - I seem to recall hearing about an issue with that but never personally experienced the problem on my YZs.

Scott

[reeseyz125]

im sorry i should have mention that. but yes it will start back up 5 minutes later and then shut back down in 2 minutes. i was thinking that something was over heating but didnt know what. so should i check the coil and cdi?. thanks...

[MXtras]

Hopefully someone else can help out here with exactly how to check these items, but yes - I think it could very well be electrical. i think it was the CDI that was a problem back then but again - I can't recall for sure and I never had the problem.

I would venture to guess you could pull the plug wire and check for spark ASAP after it shuts down - this should tell the tale. As far as whether it's the coil or the CDI - that would require either an electrical meter or simply swapping out for a known good unit. Diagnosing these heat related issues are tough because the problem might not be there when it's tested unless it's hot enough, and you don't know how hot is too hot. It does sound temp related, though.

Scott

[reeseyz125]

sweet! ok thanks....this helps out alot. ill check the spark the next time it shuts down.

thanks.

[reeseyz125]

ok....so i checked out the coil and everything seems fine but now it wont start. how can i tell if its a compression issue without a tester?. im kinda short on cash to get one so im finding other ways to figure things out. but when i try to start it, i get a short loud puff from the exhaust pipe. and when i try to bump start it the back wheel wont lock like it should. so im guessing a compression issue.

[reeseyz125]

ok i have a question about the gasket ring in the power valve or if it is a ring. can that ring cause an air leak when there is already a cover with a gasket sealing it? if everything is sealed already how would it cause an air leak?

[Ford]

reesey,

See if you can find someone with a compression tester, even one of the local bike shops can sell them for about $20/$30 and then check the specs for your bike it should read at the very lest (im going to guess) 170psi+ if it is ok for your bike?! Rememeber to when you do a compression test to open the throttle all the way open and hold it open, then have the kill switch on too and then kick it over about 5 to 8 times to get a full reading on the compression. If it is rediculously low like 130psi then you need to rebuild the top end of your bike. As for the CDI you need to check your manual it has the specs for checking the the electrical of the bike, it will have a range that the CDI should be running in. Also check to make sure your plug wire is good and not cracked or burned at all as ifit is heating up that could also be causing the problem and sometimes that happens, this is why they should be replaced about every 3 to 5 years, just like a car when you do a tune up, redo the plug wires as well, although most people dont but it is highly recommended.

Goodluck i hope it gets worked out!

Ford