Hey, all. I picked up that little Yamaha today. I've gone over the basics. Good oil, fuel, spark and basic compression. (haven't measured the compression yet) It has all the above, they just aren't all coming together.

Is there a brake safety switch or anything I should check? Anyway to override anything as a test?

Thanks in advance,
Geoff

 

Well, I got fire...just at the wrong end. I gave it a shot of ether and opened the throttle. It was a small fire and went out quickly...while I was talking to my brother-in-law phone...lol. (he got a good laugh)

How is the timing on these? Do they easily stretch their chains? Should I check the valves?

On a side note, all the research I did on these said they were 2-strokes. This is a 4-stroke... So much for research.

 

OK, correction on the facts above. There is no compression. Not enough to knock my finger off the plug hole anyway. That, combined with fire coming out of the intake, I'm guessing a stuck intake valve...? I'm hoping that's as bad as it is.

Any suggestions? Please?

 

Newest findings...

I took off the carb (on my way to the valve adjuster) and had to take the intake off with it. As I pull off the intake, the choke butterfly fell out...

Here's a theory...maybe...of what might be wrong. Correct me if I am wrong. Is it possible that the screw that formerly held the butterfly is trapped in the intake? I imagine that might stick a valve.

 

I found the screw. I thought it had jammed the intake open. Nope, it jammed both valves. They're trashed. They're so far off their valve seats that they're almost outside the head. The piston has a few marks on it but it seems fine.

 

That sucks.....but mystery solved.

 

Luckily the damage seems to be contained in the valves and dome. The screw appears to have missed the valve seats all together. I'll still clean up the head, replace the valves and parts and just keep working my way back.

Other than this, she's a cream puff...lol.

 

I've taken advantage of the machine being apart. The carb looks new, the head and cylinder are sparkling clean, thoroughly washed and lightly misted with oil. The rings on the piston are great and the piston fits up the cylinder like a bullet. I stripped the bike to the frame and wheels. Washed years of mud and grass from all the nooks and crannies, and cleaned [as well as possible] the fenders.



The new neighbor across the street is a mechanic. [I love the new neighbor] He has all the tools to re-seat the valves and is an expert at lapping them in. Hopefully I'll have the valves by the weekend and get this thing running. It took a few phone calls to find the valves in stock. I'll also have to replace the gasket for the cylinder and guess the head...since I'm throwing money at it.

Something I did not know about these is, they have no rear suspension. Anyone have any suggestions as to what tire pressure I should use in the rears to make it a softer ride? The max is 36psi.

Anyway, still moving ahead...sort of.