vespa decompression failure! uh

Ok so besides other shit that keeps going wrong at the moment...

I've got a decompression issue. I've got spark. If I take the plug out and run the bike I've got great spark, BUT when the plugs in and I pull the decomp, It's just not decompressing enough. Minimal spark...It's almost like it won't allow the flywheel to spin fast enough no matter how hard I run it. I'm running the 70cc olympia kit (with head).

I've removed, cleaned and reinstalled my decomp...any other suggestions? Can I drill out the decompression hole ever so slightly larger to get more decompression? Or will I fuck up the head?

any ideas or advice at this point will be greatly appreciated.

Re: vespa decompression failure! uh

Is the passage from the decomp to the exhaust port clear? as long as the decomp valve closes I don't see why you couldn't open up the passage. on a side note I use valve lapping compound to get a good seal.

Re: vespa decompression failure! uh

that's what I was thinking. Anyone had this problem/done this before?

Re: vespa decompression failure! uh

ᴛᴇʀʀʏ ᴅᴇᴀɴ /

i've never had this problem, but you should be able to make the hole going from the decomp valve to the exhaust port larger for more less-compression. haa.

i wouldn't mess with the hole the valve sits in, though.

Re: vespa decompression failure! uh

yeah so checked the head out today and you could see a brown spot on the head where the decomp wasn't lining up with the whole on the cylinder. So I matched them and that helped...but only a little. Then I just said fuck it and put on a 50cc head which worked fine. I think the olympia heads might just be bunk!

Re: vespa decompression failure! uh

jason is leading the field in vespa problem development. ..and solving.

Re: vespa decompression failure! uh

bet they didn't cut the channel well enough at the factory.

Re: vespa decompression failure! uh

yeah it was totally mis-aligned. Probably a 4th of it lined up.

Re: vespa decompression failure! uh

Dremel it out just enough to overlap? Or just always park at the top of a really long hill.

Re: vespa decompression failure! uh

Yeah I dremeled it to match the hole in the cylinder...still didn't do a whole lot though.

Re: vespa decompression failure! uh

jason, do you think you can put up a little "how to" for removing the decomp. i need to do that real sooon!

Re: vespa decompression failure! uh

put a counter sunk bolt in it.

vespa decompression failure! uh

kim jensen /

The problem you are describing sounds like you want more decompression so your engine will turn over, correct?

If your kit has high compression and you can't turn it over, it is because your belt is slipping! Loosen the motor mounting bolts and pull like hell, then tighten.

Try belt dressing spray on the belt to make it stickier or get a new belt!

I just as soon plug the leaky damn bastards up anyways!

kbj

Re: vespa decompression failure! uh

problem was solved with a different belt. I need to get the number off of it. it doesn't ride all the way out like the malossi does, but it's beefier and starts without slip. So for now It's a keeper.

Brad, all you need to do is take out that little cotter pin and the whole thing should be pretty self explanatory. There's a little pin that has ends that should be bent in two different directions. If you bend those back straight (which should be easy because its made from super bendy metal) you should be able to pull the cotter pin out with a pair of pliers. I recommend taking it to a local hardware store and buying a new cotter pin for 10 cents because the old ones seem like they could be hard to put back in.

Good luck.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account