A forum for owners of Yamaha TTR250 trail and enduro bikes!

Lurkville · Member

Electric Starter screeching noise after top end service

TTRfan · Super Guru

Hi Dan and sorry to hear of the problem cry

Not sure what you mean by "turning the stator anticlockwise a couple of times" as the stator is fixed in the generator cover confuse

Could you confirm that you set the valve timing correctly at TDC with the cam lobes facing outwards as per the photos 2/3rds down this page http://www.ttr250.com/Removing_Cylinder_Head/TTR_head_removal.htm ?

Can't really think of anything else without listening to the video. Maybe upload it to YouTube if you can't get Tinypic to play ball?

Brian

Lurkville · Member

Hey Brian,

Sorry- from the crankcase, when turning the motor to TDC I turned the motor the opposite direction and I heard the electric start make a squeak. The motor was at TDc, lobes outward and dashes parallel with the head.

Lurkville · Member

Here is a YouTube link youtu.be/Yb0XFnt8dps

TTRfan · Super Guru

OK - that doesn't sound good!

If my logic is correct then the sprag clutch should have free wheeled when you turned the engine backwards rather than engaged the starter.

How old is your sprag clutch and are you aware of it getting noisier recently?

What I am thinking is that, as can happen with a worn sprag, it has jammed itself on the boss of starter gear 3 such that when you start the engine it isn't disengaging and the screech is the starter motor being turned at great speed!

I hope I am wrong but a simple way to check is to take the starter gear cover off (just the three bolts) and see if the sprag is working properly. Take out starter gear 1 and try turning the exposed teeth of starter gear 2. It should freewheel one way but not the other. If it won't turn either way then the sprag is goosed.

Brian

Lurkville · Member

In the event the sprag is no good, what am I looking at as far as a rebuild or parts?

TTRfan · Super Guru

You will need: Sprag clutch and possibly generator cover gasket

See http://www.ttr250.com/Sprag_replacement/TTR_sprag_replacement.htm which will show you what's involved. It's actually quite a quick job and well within the capabilities of a home mechanic wink

Lurkville · Member

Hey guys, sorry to repost on an old thread but here’s an update— I ended up taking the bike to a shop (I’ve never taken any of my bikes to a shop other than to change a tire) however out of desperation, and with mutual friends, I gave it up to a shop. They performed a Diag and came back to say that I bent a Valve and that my spark plug threads are stripped.

The shop recommended for me to find a used motor (what?) and that to perform the work on the motor could exceed the bikes worth (okay..). To me it sounds like the bike needs a head and a set of valves.

Picked up the bike, and the valves are back in the head. I don’t have a valve compressor tool to check the valves and make sure that is the case, but as far as the spark plug threads are concerned... it looks like just the first few threads are stripped but looks like it has plenty of threads to be able to screw the plug all the way in.

Thoughts?

Lurkville · Member

Pic for reference ibb.co/XDT7GTp

mossproof · Super Guru

Don't think the plug thread is too bad, but I'm sort of in agreement with the valve theory - if a valve is stuck open, spinning the engine over with no compression can make an unusual noise. A new valve and possibly valve guide fitted by a decent engineering shop (need to machine the valve seat for a new valve). They could fit a plug thread insert while they're at it. You don't need to replace all the valves, just the bent one.
DOES NOT NEED A NEW MOTOR!! Just find an engine builder/ machine shop to do the work, rather than a bike shop which will charge you for handling, then pass it to someone else to do the work.