Acquired a PW80 of about mid 80s vintage , the previous owner ran the oil tank dry resulting in a siezed top end.

Pulled the jug to find a badly scored barrell and shot piston (not surprised).
So definately a rebore and new piston ,rings,etc but my question is will the bottom end have escaped the carnage by virtue of the top end seizing up?

Has any one got away with doing just the top end with this type of failure?

The rod has no play and i cant hear much as i cycle it.

I would love to bring this bike back to life as a spare bike for visitors or my sons mates to ride.

Pull the jug, remove the piston (<--important!) and stroke the engine repeatedly by hand. (I don't mean to insult, I'm forced to assume you've reassembled and are using the kick-starter)
If you feel any catching, sticking, popping or anything other than smooth operation, crank bearings are toast.
Order a new crank from PWOnly.com and have a machine shop measure the barrel for any ovalness and buy at least a 1 O/S piston kit (wiseco is good), but you may have more than just a 0.25mm overbore needed, that's why I'm saying have a machine shop check it. It won't cost much to check that.

The good news, is to buy the parts noted, less machine shop time, is around $220 or so for a new crank/piston
The bad news, if you need to replace the crank, you gotta split the cases. I would do that before ordering anything, you have no idea what else they neglected.

Sadly, it's hard to find a complete running engine for sale, these bikes generally just keep going, as long as you keep putting gas and oil in them.

PW 80's are tough.... I have never heard of one needing a crank before,,,if it rolls over smooth I would go buy a 40 dollar namura piston & ring kit, needle bearing and get it punched .40 and be done, to be honest I wouldn't even buy a gasket kit for the top-end, those bikes are tough, the cylinders are cast iron and seal great. 75 bucks and you should be good to go for another 10 years. That has to be the easiest engine ever designed for a rebuild, should take 10 minutes tops for re-assembly, 5 minutes of that will be setting the torque wrench.

I've got two dead ones.
Engine A was from a basket case, spark plug was removed and the whole machine was left out in the weather. If the PO hadn't completely disassembled the engine, I think it would run OK after a the crank and bearings were given a bath in motor oil. But it's disassembled, so I bought engine B from this jerkweed Dave's USA in Homassassa FL, who doesn't understand English. "Running and complete" does not mean missing a piston AND
the oil pump was bypassed and then run on straight gas. This one, at least one of the crank bearings is toast, it's notchy. I'm certain it was never running in Dave's presence, although I'm pretty sure it ran when it left the factory.

When the notches align, the engine won't kick over, the crank appears frozen. Given enough force, it will unfreeze. However, I don't think it would run without self destructing. So I guess he's not lying, his definition of "running and complete" meant sometime in it's life, just not necessarily now.

So that's the two dead PW80 motors I have. They are very hard to kill, but it is possible.

.

Quote

For MAIN bearings yes, big-ends, no.


(I have rebuilt and balanced countless TZ roadracer cranks over the years) .....

The right way to check the big-end of a crankshaft is this:

1. Remove head, barrel, piston.

2. Get the crank to BDC (bottom dead centre)

3. Rest your hands on either side of the crankcase and grip the conrod between your thumbs and two fingers.

4. Gently wriggle/twist the conrod until you feel it is perfectly centred on the crankpin.

5. Pull up and down gently on the conrod (perfectly vertically).

Now, there are two schools of thought on play here.....
a) Some say if there is any twisting possible at all then the bearing/conrod eye/crankpin are buggered.
b) Others say a little twist is ok, as long as there is no, I repeat NO, vertical movement in the assembly.

I usually go with the former for most bikes, especially the roadracers, but with these PW80s having such a thin contact area between conrod/bearing I lean towards the latter.

Greg

Thanks for the replies, i will probably take the plunge and chuck a top end in it and rebore and see what happens.

IMO top end would lock up before damage to bottom end in this case

Stickerking,

What was your end result? I have one 2 that sounds similiar that I bought.