[podger076]

Just picked up a 1985 250sx. Starts and runs great, but if I ride it for a while when I shut it off something is still spinning. Starter Bendix maybe? Still spins for a couple of seconds when shut off.

 

[retro]

Does the starter work good? Does the engine braking work when you are decelerating or going down steep hills? Only thing I can think of at the moment is a one-way clutch might be bad. You might find a copy of the factory service manual HERE for that bike.

Welcome to the forums!

 

[SamUK]

Yep, one way bearing would be my diagnosis too. If you rely on engine braking or even expect it to slow you down some when you loose off the throttle and then, it doesn’t....! Gets a little ‘butt clenching’ I have to say!
I’ve never done one but I know it involves removing the sidecase and change clutch, if you have any doubts about the condition of your timing chain this is the perfect time to replace it.

 

[shadetree]

agreed ^^^..your one-way bearing is bad, could be either side ?, you would need to listen to which side is bad ( going out ) to see which one it is ?. welcome to the forums.

 

[podger076]

250sx

Thanks everyone, time to get dirty.

 

[rednyforeman500]

Hi and Welcome to the honda atv forums!!!

 

[podger076]

One Way Clutch Bearing

Is there one of these of these on each side? I only see one in total in the manual.

 

[retro]

There is a one-way bearing in the centrifugal clutch drum (behind the right-side cover) which provides engine braking while decelerating and going down hills. When replacing that bearing the drum and hub must be inspected for wear and scoring and both of those replaced if there is any damage, else the new one-way bearing will fail. Note that there is a mark on one side of the bearing... always install a new bearing with the mark facing out. Refer to the service manual... It is Number 25 on this parts fiche:

https://www.partzilla.com/catalog/honda/atv/1985/atc250sx-a/clutch

There is also a one-way bearing behind the flywheel on the left side of the motor for the electric starter. It is Number 2 on this parts fiche:

https://www.partzilla.com/catalog/honda/atv/1985/atc250sx-a/generator

If your starter seems to be "slipping" while cranking the motor over you might need a new one-way bearing on the left side. Ride the bike and see if it fails to slow the motor while going down a steep hill (you have good brakes I hope!) and listen for the spinning noise on shutdown to learn which (or if both?) bearing is bad before buying.

Keep us updated if possible...

 

[podger076]

One Way Clutch Bearing

Both electric and kick starter work fine. The spinning noise is definitely coming from the clutch side of the motor when you shut it off. I've ordered the one way clutch bearing, and will post when I receive it and get it installed. Thanks Retro and Shadetree, didn't realize there was a one way bearing on the starter side as well. Great forum with knowledgeable people.

 

[retro]

One more tip: Those one-way clutch bearings sometimes come apart (when they are shot) when you pull the centrifugal clutch apart. Prepare yourself for a gazillion pieces scattering just in case... plug the holes at the bottom of the crankcase with rags so small parts don't take a bad bounce and roll inside there while you are distracted by scattering pieces. While you are waiting for the new part and cover gasket is a good opportunity to read up on the job in the service manual. Have fun with it...

 

[podger076]

Thanks for the advice! The Starter one way bearing not available on Retro's post. Any ideas just in case?

 

[retro]

As far as I know NOS or used parts might be your only options in that case. If its any consolation, the starter side one-way rarely goes bad on a well maintained motor. Good used ones with the matched flywheel might run about $40-$50 or so...

 

[podger076]

Found an NOS on ebay for $190. Will start looking for used with a flywheel. Something I don't understand. Both Kick and Electric Starters work just fine. Should one of those not be an indication? I'm going to take it out tomorrow and see if the motor slows it down going downhill. Thanks for the advice, this isn't in the manual!

 

[retro]

Yep, if your electric starter works fine then there is nothing wrong with the one-way clutch on the left side. They rarely go bad unless the motor has been poorly maintained, so you'll probably never need to replace that one.

The right side engine braking one-way clutch failures are much more common. Thankfully you can still buy that one... even though it is priced quite high.

 

[podger076]

And the downhill test should prove it?

 

[podger076]

Sorry, just don't want to cause any damage, and I'm anal about everything working properly. I get out first thing, and try the downhill. Will post results.

 

[retro]

Yes, any downhill deceleration should pull the RPMs down. You can do the same test without a hill by letting off the throttle in any of the forward gears at speed with the motor revved a bit. In any of those tests if the motor immediately returns to idle without slowing the bike down (the bike continues to coast at high speed), the one-way in the centrifugal clutch is bad.

Incidentally... if you end up having to take the right side cover off to replace the one-way clutch bearing, you may as well check the condition of the cam chain before you begin that job... in case the cam chain needs replaced. The reason for that is you'd be taking the centrifugal clutch assembly off from the crankshaft.... the cam chain is right behind that clutch on the crank sprocket, so if that chain were worn out you'd save yourself the same right side teardown work in the future. Checking the cam chain condition is easy... we can help you do that once you learn whether you need to fix that one-way or not.

 

[podger076]

Have added a chain as well. Better on hand than to wait.

 

[podger076]

Think I'll stock up on common parts. I'm very happy with it, and will pick up another one for myself. The wife just claimed this one as hers.

 

[retro]

Were you able to find an OEM Honda cam chain? You can buy a D.I.D. chain for less than OEM price if you can't get OEM... they are very good chains. The cheap china stuff won't last long.