I was taking my RB R3 engine apart to give it some maintenance and check internals after the last time I used on my 720 and There a pretty big scratch on the sleeve and the piston.

What could have caused this?

The engine has about 2 gals thru it, I can feel the piston still fits tight inside the sleeve but what will happen with performance now?

What should I do? piston and sleeve replacement it's expensive I rather just buy a new engine. should I just keep running it? I haven't started it since I put it back together.


Thanks!

ever blow a plug? clean/replace your air filter regularly?

just guessing a blown plug caused it if it is a fairly deep scratch.

fhotos..
maybe you can save it with a honing and resize.
maybe!

No blown plugs on this engine ever!

I clean the air filters after every race day... I think I forgot to add filter oil the last time!

I will take some pics tonight and post them! the scratch is fairly deep looks like it might have been made by a piece of metal perhaps a little bigger that glow plow element. After putting it together I turned it with the flywheel on and it is still feels a bid tight but seems like compression is no longer there!

Looks like there may been some debree on the button head when you re-inserted it into the sleeve. The top of the sleeve shows some nasty scaring.

I would lokk at a new piston and sleeve set.

Yeah that's some pretty nasty damage. I had a hard time finding P/S sets and they are quiet expensive! I think I rather buy another engine

So, what if I just keep running it like that??

I doubt it will run very well. I have seen motors with lightly scratched pistons continue to run well but that looks pretty bad. The only hope is to use a fuel that leaves a lot of carbon buildup behind to fill the scratches but I doubt even that will help with this one.

Also, if you do decide to rebuild it, check your rear bearing.

Looks like a damaged chrome layer and pieces of the chrome were wondering arround in the engine.

Looking into the damaging I think the buttonhead was not placed straight and then the head was with lot of force screwed on to it.

And it seems there is a tear in the piston so it will never run reliable

I would just run it the scratches at the top are the ones you need to worrying about !!! 800grit the piston just on the top just to smooth the big one . then see how she runs

+1 looks real bad good luck

I was also considering changing the piston only since I have a V12 standard plug that I don't even use. You think that might work better?

I've been looking for P/S sets on the net but no luck. I found some site from Europe but since its en Euros it comes to almost $240 with shipping... I don't think its worth it! maybe if it was the R3 RC version... What do you all think?

...maybe I should just use it as paper weight

I don't see why hot if your going to use the piston and sleeve

Try reaching out to Murnan he might be able to help you out since he does a lot of mods on RB's He might have a P/S set