Vintage Dirt Bike Q & A

Please help....I picked this bike up for my son and after 1/2 day of riding the bike really lost power in 1st gear, it eventially got to were it wouldn't run at all. I bought new points and condensor (OEM parts) and had them installed and the bike runs really good for about 10 minutes (until warm) and then the bike really bogs down in first gear, once you get the rpm's up, it will go on, but it will barely pull itself from a stop. Can anyone tell me what to check next?

Thanks,
Brent

Could be a lot of things but the first I would check would be the jets. Just take the carb off, remove the 4 screws from the float bowl, and you should be able to unscrew/remove the brass jets. You don't even have to remove the throttle cable if you are careful.

If you find any crud in the bottom of he float bowl, that is or would have soon become the problem.

How many miles are on the bike? What kind of shape is the top end in and does it have good compression? The silencer and exhaust port may be carboned up. Did you check your point gap? If the carb is clean,fuel filter in the tank is clean, air filter is OK and exhaust system and port are clean, you could also have a condenser going bad, your coil may be breaking down, I've even had a source coil in the magneto get weak and do the same thing. You could even have something as simple as a bad ground between your coil and frame. These bikes are getting up in the years now and can throw some wierd tantrums, most of them are electrical. Just follow a good troubleshooting guide like you would find in a Clymer or Chilton manual, don't do anthing drastic or desperate and you'll find the problem.