Motorcycle Repair: Questions about 1985 Honda Rebel 250, honda rebel 250, air filter element

Question
Mr. Silver,

I just bought a 1985 Honda Rebel 250 to fix up.  When I bought it it had been out in a field for at least a full year.  It wouldn't start and it looked awful.  After getting started I've run into two problems (they might be related) and I wondered if you could help.  

First problem:  It seems to not be getting enough gas.  Sometimes at start it doesn't act right and then at the top end of gears it will stop accelerating.   It will not accelerate over 35 mph.  

Second problem:  The bike makes a noise when it goes into third gear.  The noise continues through the gear.  Its like a low pitch scrape.  

If you have any ideas on these problems I would greatly appreciate it.  What's my next step?

David

Answer
David, you need to remove the carburetor and clean it thoroughly, change out whatever old fuel is in the tank and replace the fuel filter screen in the petcock/fuel tank connection. There is an accelerator pump diaphragm in the carb that needs checking, otherwise it won't take throttle very quickly.
http://www.bikebandit.com/houseofmotorcycles/honda-motorcycle-cmx250c-rebel-1985...
for references to the different systems and parts of the bike.

You didn't say how many miles are on the bike, but they usually go a good 50k miles without major failures, if the oil has been changed regularly and the bike has had maintenance. Check the air filter element, which may have fallen apart by now. Any changes to the intake or exhaust system will harm performance.

If your gear noise is only in 3rd gear, then there may be damage to that gearset. Get the back wheel up off the ground so you can check for tightness or excessive slack in the drivechain, which can create scraping noises under varying throttle conditions.

Drain the oil and look for signs of metal debris, which indicates serious engine/transmission damage inside.

Bill Silver