MOPED ARMY

Honestly dude, I've been running JB weld on a puch polini for over 3 years and it's good. I know Chris Rice has had JB blocking off an entire port on his Vespa Sprint for at least 4 years...don't discount the JB man. Yes, many many people use it incorrectly, but if you use it properly you can have amazing results.

Don't tap it, if you do that you will probably do exactly what you are trying to avoid, fuck with the bore...tig it or jb that shit right up.

I tapped the deconpression hole on one of my puch 65 metras and it had been overbored twice. The hole actually looked closer to the bore. Make sure to get that tap strait and keep it lubed. I threaded in a set screw with high temp rtv in the threads, then I covered the top of the screw with a little more RTV sealant just to make sure it sealed off tight.

I havn't had any problems yet. Actually, I solved the air leak I had because the bore was so close to the hole.

good luck,

Eric

i know you said its for your custom head.

but what reason would any one have to do that . what does it do

I think tap and a set screw would work well, and use some red loctite on that thing. The only kind of torque problems warping the bore I could see happening are if you use a really long set screw and bottom it out against the back side of the cylinder. With a short screw I doubt it would have that problem.

I would just tap it.

The heat from the weld will be pretty intense too, but I've welded studs into my scooter's polini kit.

i had my motobecane cylinder tig'd up like crazy, and it was fine. Good point though, this is obviously too close to the bore so welding is out of the question.

There have been some good ideas on this thread thanks for all the suggestions. I will look into my tap collection to see if i have the perfect one.

Fair enough, I put locktite on the setscrew when I put them in, and I don't tap the hole all the way through so there is no way in hell the screw can drop down into the exhaust port. Seems like a good idea. The only thing I can think of being an issue is being that close to the bore is the rate of metal expansion due to heat will be different from the cylinder and the setscrew, and may cause the cylinder to be tight there. But we're talking super small amounts that'd I'd write off and not worry about.

Yeah it's such a small amount of metal it shouldn't expand that much. Good luck!

-naz

great idea chuck! i can always thread some alu rod through a die and make my own!

could you put a piece of metal round stock thats like half a millimeter to big or bigger then lathed down.

then freeze the plug and put the cylinder in the stove. and it should block it with no holes.