441cm piston stuck in cylinder

[imagineero]

OK,
So this one has me buggered. Stripped one of my 441's down a couple weeks back because it had a weird sound coming out of it. No big deal, turned out to be a bit of crud bouncing around the crankcase. So I cleaned the crankcase out and put it back together and that's where the fun begins. Piston is now unable to go fully up and down in the cylinder.

In all the excitement I may have put the piston in backwards, haven't checked. crank rotates freely, but only to a certain point, where the piston will go no lower. Unbolted cylinder, and can verify that it is indeed the piston being unable to move and not the crank. Piston will only move down so far as the bottom of the skirt almost covers the bottom if the intake port, and no further.

I guess it's possible that the cylinder/piston has a burr stopping it travelling further? Other than that, no idea.... any clues about how to proceed? access is a little awkward, can't easily see any way to get to the circlip on the conn rod. No hurry to deal with this, its been on my "to do" list for a couple weeks now.

 

[BuckthornBonnie]

Did you use a piston stop at all in the process? A piece of the rope stuck in a port?

 

[Ozhoo]

You can usually rotate them slightly to get em past whatever is binding it up. Any chance that you left out a circlip and now the wrist pin is stuck in a transfer port?

 

[s sidewall]

Can you turn the cylinder, exhaust port to the rear or left or right, line port with crankshaft?

Steve

 

[imagineero]

Did you use a piston stop at all in the process? A piece of the rope stuck in a port?

Nope, buzzed the clutch off with a rattle gun. Good thinking though!

 

[imagineero]

You can usually rotate them slightly to get em past whatever is binding it up. Any chance that you left out a circlip and now the wrist pin is stuck in a transfer port?

I’ll have a look at that this weekend, from memory I couldn’t get the cylinder up high enough to clear the crank case and be able to rotate it but I’ll look again. Anything’s possible, I guess the cue lip could have popped out. Doesn’t seem like the wrist pin stuck in a transfer, it has quite a bit of up/down movement. Just can’t get the skirt below the bottom of the intake port. Certainly worth a look at! Thanks for the ideas...

 

[HarleyT]

Did you try to remove the clutch with the cylinder not bolted to the crankcase?

 

[CR888]

I had this issue with a strato blower when I fittest the intake manifold without its gasket. That allowed a fastener to go further toward the cylinder than it should and pressesd into the bore liner. This stopped the piston going fully up & down but the crank moved freely until it would snag up. I know their two different animals but something I thought I'd share. I ended up fixing that cylinder and its lived a long life since.

 

[HarleyT]

I had this issue with a strato blower when I fittest the intake manifold without its gasket. That allowed a fastener to go further toward the cylinder than it should and pressesd into the bore liner. This stopped the piston going fully up & down but the crank moved freely until it would snag up. I know their two different animals but something I thought I'd share. I ended up fixing that cylinder and its lived a long life since.

Dang. Was it a real thick gasket?

 

[imagineero]

Did you try to remove the clutch with the cylinder not bolted to the crankcase?

Yeah,
I had it stripped down to just a bare case before reassembly, recoil, clutch, whole intake side, muffler all off. So when I got it back together that was the first thing I tried - strip it bare again. Will have a look at it over the weekend, you guys have already given me some pretty good ideas to start working with, plus I've gotten less in a hurry now a couple of weeks has gone past. Being less in a hurry always helps from my experience.

 

[CR888]

Dang. Was it a real thick gasket?

Not really but there was 3 fasteners in a triangular shape for a strato manifold on a BG86 and the top centre one pushed into the cylinder cracking open the nikasil. I pushed it back JB'd the base of fastener and fingered it with sandpaper until smooth.

 

[HarleyT]

fingered it with sandpaper until smooth.

Works on a lot of things....

 

[imagineero]

Been quite a while since I posted this so I started a new thread with new info and pics here;

https://www.arboristsite.com/commun...-in-cylinder-again-bearings-destroyed.322346/