how to tell if the crank seal is bad????

[vez]

Can any one tell me how to check for a bad crank seal on a 2001 yz 125.

 

[muddy226]

If the crank seal is bad on the transmission side ( which I think is what you are asking ) transmission oil will be sucked into the crankcase and burned. This should be obvious as the bike will be producing loads of smoke even when properly warmed up, and the oil level in the transmission will noticably reduce.

 

[vez]

If the crank seal is bad on the transmission side ( which I think is what you are asking ) transmission oil will be sucked into the crankcase and burned. This should be obvious as the bike will be producing loads of smoke even when properly warmed up, and the oil level in the transmission will noticably reduce.

Thanks, but it really doesn’t smoke too badly when its warm. Should I just have a leak test done and forget about it or would you recommend rejetting it first?

 

[reelrazor]

What are the symptoms that make you suspect that the crank seal is bad?

 

[vez]

What are the symptoms that make you suspect that the crank seal is bad?

Fouled plugs everytime I ride. The plug is wet and black. If I let it lug down just a little or if I drop it and it stalls when I restart it it will run for about 20 seconds and bog to a stop and wont't start until I change the plug.

 

[reelrazor]

Has it always been like this? Did anything change and then this started? ??

 

[vez]

Has it always been like this? Did anything change and then this started? ??

I just bought the bike. It has done this since the first time I rode it.I've had it out about 5 times and I've went through 9 plugs.

 

[vez]

Has it always been like this? Did anything change and then this started? ??

If this is something that you can help me with I would really appreciate if you could e-mail me at vez@adelphia.net. Thanks, jim.

 

[reelrazor]

YOu need to start with the basics. Clean the carb, well. Air filter too. Eye the reed valves while you have the carb off. Pay special attention to the air bleed passages in the carb(opening/s at the carb throat that mix air with fuel in the pilot and main jet wells). Write the numbers of the main and pilot jet down while you have them out of the carb. Remove the needle jet to clean the carb(they aint clean clean unless you do). Check where the float level is before you remove the float/s. Note where the needle clip is placed and the setting of the fuel/air mixture screw.

Armed with this info and the knowledge that the carb is clean, the reeds are good, etc. you can run it and see if it is any better. If not, you can then make a decision on re-jetting it properly.

 

[MikeT]

reelrazor is on the right track. Air Filter first. Lightly oil it, then put in a new plug and you need to probably rejet it first. I think you have some jetting issues.

 

[billtx]

I had a bad crank seal on my YZ125. You may or may not have one. When you do all the other stuff mentioned above, change your tranny oil. Measure what you put in - should be 650CC. And then change it after you ride and measure what you take out. Mine would lose 200-300cc after about 20 minutes or so - way too much. It started running right when the oil level went down and it could not suck it into the crank.

Note that this can throw your jetting off also. Unless your bike is modified, verify that it has the stock jetting in it. This would be a good starting point.