Worth fixing?

[u/justinltl]

Hi guys,

This is my first time working on an engine. It's a Kawasaki z800 and my piston had a meeting with a valve. Not sure if the valve clearance was wrong or if it jumped timing or something else. If it did jump timing is it possible only 1 piston hit 1 valve? My idea going forward was a new cylinder head + new piston and timing chain. The cylinder itself somehow is not that badly damaged, only some minimal scratches around the top, is it too bad? The engine ran for 15 minutes after it happened just getting home. Is it worth fixing this engine or just get a donor engine? There is not one available at the moment on the market so I would like to try fixing it. Any help/thoughts is much appreciated!

[u/strangerimor]

I have a feeling the valve failed resulting it dropping into the cylinder. I've seen some discussion about this exact thing happening on certain Kawasaki engines in the past. There was some specific years of engines which had this possibility.

As for saving the engine I think it is a lost cause. Cylinder head is not saveable by any means of reasonable money. The parts and work would quickly add up so if it were up to me I would definitely buy a good used one and keep the old one for the parts that didn't break.

[u/riley_3756 → u/strangerimor]

Had this happen in a piece of machinery too, timing and valve lash were fine but either the retainer or valve failed and just dropped into the cylinder. I had wayyy less cylinder damage and was able to bore .030 over, new head and cam etc. The only reason it was worth it is because I run a machine shop and was able to do the machine work myself. Otherwise a new motor would have been cheaper.

This kind of damage would be at least a head and sleeving the cylinders, plus cam, lifters, etc. They would probably be able to buy another engine for less.

[u/tater5761]

I'm not an expert but in pictures 2 and 3 there looks to be damage at the very top of the cylinder. I don't think you would ever get this right without a lot of money

[u/texan01]

Unless it’s super rare, I’d look for a donor.

[u/1crazypj]

Unless your a good welder and have a machine shop, not worth the cost of paying anyone to do it.

If it was something irreplaceable and worth a lot, yes, fix it.

repairs would cost more than complete used motor

[u/Kitchen-Difference79]

I would never just replace one piston. Have it bored, replace all pistons. Find a good used head. Have new valves, valve guides and seals installed. Seeing how the piston made contact with the valves I’d probably replace the rods as well. I’ve never tore apart this particular engine but I’m guessing the crank is pressed together. You’ll have to find someone that can disassemble it, put new rods on, press it back together and true it up. Don’t cut corners or you’ll be back on here asking for advice again in a short amount of time. Those bikes are out there for sale wrecked. I just sold a good running totaled one for $500.

[u/Ok_Maintenance_9100]

Completely toast. Nothing there can be saved without spending I’d say 5x what the cost of each part new or used would cost

[u/M_Rose728]

That cylinder wall looks like it has some deep scratches. Not good.

[u/Felix995]

Sucked valve. Looks pretty rough, I think that one could be a bit too far gone. A good used engine is more of a viable alternative, I think.

[u/justinltl]

Alright guess I'mma start searching for donor blocks, thanks for the opinions!

[u/AviatorDave172]

If the damage at the top is above the top ring land and the sealing surface is ok, the cylinder may be useable. The head is a goner.

[u/ApricotNervous5408]

Only if it’s super rare.

[u/Responsible-Shoe7258]

I would be looking for a wrecked bike engine donor.

[u/Confident-Benefit600]

Eeeuuuuuu, absolute junk