Old Dirt bike
 

Wasn't sure which part of the forum to put this in (maybe OT?) so I'll just ask you guys. I have a 10 year old dirt bike, it's a little 125cc. I can't get it to stay running. If I spray the carb with b-12 cleaner the bike will start up after a few kicks. But no matter how much throttle I give it, it won't run for more than 5 seconds. Any suggestions?

What kind of bike? I raced motocross from when I was 12-19. Best sport in the world hands down. But thats all going to go down the drain with the new lead ban....

As for your problem make sure all the jets are cleaned out and give the whole carb a good cleaning. Make sure it has good gas. Old gas can clog a carb and make it hard to start. Check the plug it may be fouled as well.

It's a yamaha. The spark plug has really close spacing and the tip doesn't quite line up. So I should take off the carb and clean all the parts?

It can only help. 2 strokes are a piece of cake. Its either the carb or the head. If you have a bad head gasket and air is getting in it will also make it not run. But I would start with the cleaning the carb and the jets first and go from there.

I took apart the carb as much as I could and sprayed a lot of cleaner on it. The "bowl" on the bottom of it was filthy inside, and dry, don't know if it should be or not? Put it back on and it didn't seem to help.

Did you clean the jets? Try cleaning the jets, new gas, and a new plug. If she doesn't fire, it may be the head gasket. Which unlike in vehicles, is cake to change.

Also try pouring a little gas in where the spark plug goes. If it runs for a bit, basically until that runs out that can tell you its somewhere in the carb/gas.

If after all that fails, you will have to look at your rings and piston. The nice thing is this is all real easy and cheap on a 2 stroke. Once all motocross bikes changed over to 4 strokes the sport got too expensive between the fact that parts were 2x as much and 2x as much mateince is needed.

How do I clean the jets? Sorry, don't know much about carbs.

check the pitcock.....hum i sure hope i spelled that right....thing under the gas tank that turns fuel on and off and resever. and check fuel filter if the bike has one


o and if the bike satup for say over a year or 2 with gas n it. you have to replace all lines clean out pitcock vaule and clean out the carb. jets in all.

Well first look at the main jet, the one right in the bowl. Just losen it up and take it out and if you can't see through the hole its clogged. But blow it out and spray with carb cleaner.

And like jar said, obviously make sure the gas is turned on.

If the bowl is dry, you are not getting fuel to it, work upstream to find out why. pull the fuel line off the petcock and turn it on, do you have fuel? put it back on and pull the line off the carb, do you have fuel now? put it back on. remove the float bowl drain plug and turn on the petcock, Agian, FUel present? if not, the float pin is stuck. Most likely the float is stuck because it sat so long. Take the carb apart and remove the main jet and pilot jets and clean them out. If your bike is a YZ125, it probably has reed valve induction.
Go to the Yamaha website and get help there. You do not have an issue with head gasket or rings if it starts, they may very well need to be replaced, but if it starts on a spray, thats not your imediate problem.