the PA50 dies

too bad.. the PA50 ate a piston ring today .. (at least thats what I think happened .. haven't done surgery yet)

I pushed/coasted it home after it made a few loud mechanical sounding 'hiccups' at 40mph .. and I shut it down

I had kind of overlooked the fact that the top end on the PA had previously sustained a major seizure ... the top end came from the parts motor I bought that at first looked beeyootifull .. till I disassembled it... and found it had had a major seizure.

.. and I had to file the piston to get it to 'release' the rings from the aluminum that was smeared over them.

I re-used all those old parts after a careful 'clean-up'.

I had been treating the motor like it was all in tip-top shape.

I had changed the variator yesterday .. and it was revving a lot higher now at top speed.

Shouldn't really do that on parts that have been damaged before.

I bet the bottom ring broke right where I had to file it a bit.

Shouldn't be too bad to fix .. depends on how bad the bore got 'bit'.

The bright side ?... I've never had a moped motor that hadn't been seized a few times before I got it.

So this will be my first new piston and bore in a moped ever.

(actually .. I'll swap back to the 'old cyl/piston first.)

Maybe the 50mph PA will be a little faster with a new top end ?

Re: the PA50 dies

ItsLookingUp /

Too funny... You should be able to get those NEW (slightly used) parts doin 60 mph. That's right, if everything is tight you can do SIXTY! I'm glad to see you can look back, laugh and learn. Thank's for the lesson, I've got some old parts that are working so well together I push them further... I'll stop!

Re: the PA50 dies

The top ring was in pieces.

Bottom ring "OK"... but now jammed in its groove.

Small section of the piston ring land broke out.

One wrist pin circlip jammed into the spark plug .. (I don't think thats where its supposed to be!)

From the looks of it the top ring had busted before the circlip came loose.

Cylinder's not bad .. has two small grooves (made by the circlip I'm sure)

Both should clean up with a 2nd over piston and bore.

maybe a piece of the ring knocked the circlip loose .. or maybe the circlip helped break the top ring.

Re: the PA50 dies

david f martin /

The circlip got past the rings, to the top of the cylinder?

Weird...

You've definitely got the right attitude, though. I hate having to push the bike when it breaks, but I don't mind fixing it (and making it better).

david

Re: the PA50 dies

david f martin wrote:

> The circlip got past the rings, to the top of the cylinder?

> Weird...

Being a 2 stroke .. there are big holes in the cylinder walls that let all kinds off stuff be .. underneath the piston one minute .. above the piston (and out the exhaust port).. the next.

So the circlip popped out into a transfer.. then up into the combustion chamber .. and at sometime got jammed between the piston and bore.

That circlip was strected almost straight.. and stuck in the spark plug !

As much fiddling as I've done to this motor .. I can't be mad or surprised .. I also re-used the circlip the last time .. (not recommended)

Check this out >

I once found a penny in the combustion chamber of a 4 stroke 4 cylinder motorcycle I was riding.

(my fault by a measure of carelessness)

Re: the PA50 dies

david f martin /

I hadn't thought about the ports on a 2 stroke... Makes more sense to me now.

A Prelude belonging to one of our mechanics sucked up a metal part of the aftermarket K&N filter into the intake. Fortunately it was too big to make it to the intake valve, but it was blocking the flow to one of the cylinders...

Took him awhile to figure out what had happened.

Could the 2 small grooves in the cylinder have been caused by the wristpin getting out of place?

david

Re: the PA50 dies

david f martin wrote:

> Could the 2 small grooves in the cylinder have been caused by the wristpin getting out of place?

Nope .. they are far apart .. one is on the back of the piston .. on the center of the 'back transfer' .. wrist pin is no where near that.

Re: the PA50 dies

david f martin /

Right at the port. Yup, had to have been the circlip. The other groove was caused by the broken ring?

david

Re: the PA50 dies

david f martin wrote:

> Right at the port. Yup, had to have been the circlip. The

> other groove was caused by the broken ring?

Naw ... I'm positive they were both caused by the same circlip ... at 9000 rpm .. the piston would go up and down 750 times in the 5 seconds from the first 'noise' till the second when I shut it down .. plenty of chances for that circlip to pay a few visits to just about every location .. any parts of the ring would have done more damage than these small narrow grooves.

... and I heard 2 distinct noises .. theres my 2 grooves .. and I should have shut it down at the first noise.

Re: the PA50 dies

david f martin /

Wow, sounds like it could've caused a lot more damage than it did.

david

Re: the PA50 dies

david f martin /

Are you gonna be able to get a 2nd oversized piston and rings?

I know you've discussed this before, but I don't remember what you came up with... Or maybe it was about using a larger bore from another bike...

david

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