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Old 09-18-2011, 09:25 PM   #100
bmwhacker OP
Still on 3 wheels
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Originally Posted by tenderfoot View Post
I don't know if it's a better idea, maybe an alternative.

First off, I'm no engine rebuilder my experience is of the more brutal steelmill maintenance kind.

So, I would start considering jacking the bloody thing off using one of those small Enerpac type hydraulic jacks.

The pistons don't appear to be at TDC so if you loosen the cylinder bolts on both sides, the crank should rotate enough to establish a gap between the crank case and the bottom of the cylinder.

If the gap is large enough for two pieces of stout flatbar to be inserted one above the other below the conrod, I woul use these a bases to attach long enough pieces of threaded bar sticking out past the cylinder.
So now you have four long bolts (one on each end of the flatbars) sticking out past the cylinder. Fabricate some kind of base connecting the four studs and use this to anchor the jack.
Ideally you should use a pipe which just fits inside the cylinder to apply the force evenly on the circumference of the piston as a concentrated point loading may cause damage.
Don't be tempted to use the headbolts as it would be a catastrophe if you were to strip them.

Better advice may be to just take your problem to the Garage section, those guys know what they talk about.

Thanks for the input.
Today I did loosen the cylinder base nuts a half inch or so with the hope that the pistons were on an outward stroke, which would have moved the jugs outward. Unfortunately I didn't gain anything when I rocked the rear wheel (hoping to move something).
That is why I am afraid I might have a rod seized to the crankshaft, but.... The previous owner told me that the engine did turn when he acquired the bike. The bike then sat for 20 years in his garage. After sitting for 20 years I hope it doesn't take 20 years to "thaw" it out. The cylinders have soaked with Marvel oil on and off now for 5 months or so. The pistons each have 5 rings so it appears that they don't want to let go of the cylinder walls. More patience needed I guess.
I'm a little concerned about violently rocking the rear wheel back and forth as I don't want to damage anything in the transmission or final drive. I've used this technique before with success on a rusty conventional 3 ring pistoned BMW engine.
Maybe heating the cylinders might be another method?
If I could get the cylinder to expand without the piston expanding?
I wonder if a heat gun would be enough to expand things?
A torch might be too much?

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