Just won't start

[gonzo_303]

So I finally got the engine put back together on my XS400SG special 3F9 11/79 1980. Upon trying to get it to start, it would try with some starter fluid. As long as I was holding the starter it would try to fire and as soon as I let go, nothing. Has good spark on both sides, compression test gave me these results: Dry: 90 / 95 Wet: 180 / 180. This was after a full tear down, so I know the pistons aren't stuck. I assume I need a ring job (ha)? Would compression that low cause a no start? TCI looked like it was in good condition when I opened it up no loose connections or broken solder. I setup timing by following the steps in the manual to a T. I'm scratching my head here... almost ready to bang it against the wall.

 

[amc49]

Compression looks dead, the big difference in adding oil shows you likely added way too much of it, enough to lower volume in the chamber. getting close to blowing a head gasket doing that.

 

[gonzo_303]

It was about a tablespoon added through the spark plug hole.

 

[amc49]

Then you have a problem. I've run compression on hundreds of engines and the norm for wet compression coming up is maybe 20-30 psi. Certainly not that much, I've never seen that degree of difference unless too much oil went in. It lowers the small bike engine volume enough to push the number that high.

As well, if no fuel coming to back up the starter fluid well of course it won't light off.