Hole in 288 cylinder repair

[bnmc98]

So, I have discovered a bad thing. My 288 has a hole in the decompression valve chamber that is giving me woes. (see image)

Looking for some advice. I tried a high temp thread sealer and it just turned it to ash. Was thinking of J B welding the plug into it and sealing it that way. But, I don't know if that will burn up too and cause a larger problem. Says its rated to 500 degrees.

Background:
- it does leak through the hole.
- This is supposedly a newer rebuild, my guess is that it is an aftermarket jug because it looks like a casting flaw to me.
- its a work saw so I don't care how it looks, I just need it to seal.
- cheap is good, don't really want to put a jug on it.

I am concerned because it looks like there is not a factory replacement avail for this saw, and I don't know what piston is in it so I don't know if I want to put a new jug on it. ( don't know if that would cause compatibility problems)

any advice would be great
Brian

 

[Rockjock]

looking at the pic I am not sure I see it. So it is leading out the side?

 

[bnmc98]

yes it is the dark rectangle where the arrow is pointing, right where the threads turn to the dish.

 

[treesmith]

Does it affect it while running? Can you block the whole decomp with a bolt?

 

[cgraham1]

Did you try one of these?

 

[bnmc98]

There is a plug that seats in the dish and a nipple goes into the hole toward the chamber. once that is threaded in, and tight, it still leaks. I can spray stuff into the hole in the side and kill the saw.
when I put the tread sealant in it and it burned up the sealant, the nipple broke off in the hole and I had to pound it out into the chamber even and pick the piece out with tweezers. but I have the rest of the plug still. I don't think I can use a decomp the way it is.

 

[bnmc98]

This is whats left of what I have, basically same thing you showed me. its rounded on the end to fit in the dish. Just missing the nipple now.

 

[rmh3481]

Try a couple round cut outs of copper flashing under that bolt.

 

[bnmc98]

you mean something to just plug the hole to the cylinder? Where do you get copper flashing? And will that withstand the heat?

 

[rmh3481]

Copper flashing at the lumber yard. Yes, will withstand the heat. Seal the threads with loctite and it should hold.

 

[mdavlee]

JB weld may hold up. A welding shop could spot it with an aluminum spool gun in 30 seconds if it was cleaned up good with no oil or residue left.

 

[wcorey]

You could try something like a ball bearing or a bb held against the decomp hole with the plug.
Could likely get away with a wad of aluminum foil squeezed in to near solid instead though.

 

[Big_Wood]

what RMH3481 is saying is to cut a round disk of copper flashing the size of the threaded portion so the bolts squishes it creating a seal not stuffing the small hole with copper . would sure suck bad to get a chunk of copper bouncing around the combustion chamber. copper is an excellent gasket meterial and is used in head gaskets as well. i've experimented with JB weld in exhaust tracks of outboard motors. around here they corrode away to nothing in a few years if the cooling system zincs aren't replaced every so often. we've experimented rebuilding sections of a rotted section of a 4 stroke block where the exhaust valves release combustion gases (hottest spot on the engine). on the other side of that wall we repaired is where the cooling system picks up ice cold ocean water. i figured with the temp differences between sides of that wall the JB wouldn't last 10 min. 4 months later the JB finally took a dump. when i say it'll work in this application i would hope that you would believe me LOL. i now have a buddy who TIG welds rotten outboard blocks for me.

 

[2stroker]

You may try an auto parts store for copper washers that are used on banjo bolts for the brake line connections to the caliper.
You may get lucky and they'll have the correct size.
2stroker

 

[Rockjock]

Permatex, Dirko, Threebond, Yammabond all should work. on the threads and the mating surface .

 

[bnmc98]

Welp, I cold welded it with JB. I will see in 24hrs what she does.