1971 honda sl100 seized engine

[slag]

I bought this bike from my neighbor with the seized engine. Got it all broken down and yep, the piston is rusted to the cylinder. The bottom end is smooth and feels good, but man, that piston is stuck as hard as it can be. I've soaked it in pb blaster for a week and pounded on it with a sledge and block of wood and its not coming out.

I've read where you can put it all back together and force the piston out with a grease fitting in the spark plug hole, but my spark plug threads are also stripped out and I'm not going to just helicoil the opening.. I'm going to use a special zerk fitting the F150 guys use on their trucks, so for now, thats out of the question.

Any other ideas or tried and true procedures? I do have a propane torch but not sure that will get anything hot enough to matter. I might need to take this down to the machine shop.

 

[Vette73]

Yea I was going to say heat the block up and then hit it. The heat should also break some of the rust up. BUT it could also be badly rust welded. If thats the case you may break more then just the rust weld when it comes apart. So be careful.

 

[AMCRambler]

Besides the propane torch you can try a mapp and oxygen torch. Home Depot sells a Benzomatic brand kit that's got a mapp tank and a disposable oxygen cylinder with the hoses, tip and everything for like $60 bucks. That sucker gets pretty damn hot if you want to try heating the hell out of it. You only get about 25 minutes worth of oxygen with the tank but it burns hot. I picked on up to do some brazing on my car project.

 

[bruceb]

What you need is a chemical called: Methyl Ethyl Ketone
It is specifically intended to break up hard carbon deposits
in an engine. Use in a well ventilated area.

 

[ivan2]

is it possible to, hmm, get a sledgehammer and knock harder?

 

[compman25]

is it possible to, hmm, get a sledgehammer and knock harder?

The right tool is always the next size bigger hammer!

 

[cardiac]

Why not just pick up a new cylinder and piston? Here's a used cylinder for cheap: http://cgi.ebay.com/ebaymotors/71-H...rcycles_Parts_Accessories&hash=item5ad8b3af10

$22.50 buy it now. New Piston/ring sets are like $25

Bob

 

[slag]

Why not just pick up a new cylinder and piston? Here's a used cylinder for cheap: http://cgi.ebay.com/ebaymotors/71-H...rcycles_Parts_Accessories&hash=item5ad8b3af10

$22.50 buy it now. New Piston/ring sets are like $25

Bob

Thats what I'm going to do, however, I need to get the old one unseized first so I can remove the cylinder and then piston from the connecting rod. Gonna try for 2.0 tonight. I don't want to damage the crank bearings or connecting rod bearings though.