Modern Vespa

Can anyone tell me what the compression reading should be on a stock VBA?

Soooooo... Same as any other? 100+?

I'm only getting 80.

Soooooo... Same rings & cylinder as rec'd, no?

Yeah, seems low. I had low compression on my Rally. $5 set of rings & $15 hone made a huge difference, not perfect but good at least until I can do a new top end.

Pull the studs, don't even drop the motor. Lap your head while you're at it if not already done. 2 or 3 hours + waiting on the hone job. $20 ghetto top end rebuild, highly recommend since I just tried it.

Is it taking a lot of kicks to get it started? My small frame started easily at first and read 120 PSI, then after a bit it would take 30 kicks to get started. After that I took another compression test and got 80. Hence the teardown and the patient waiting on the Sip cases to be available.They are robust engines and will run like that for awhile, so if it's running ok like that, just go with it for awhile. I wish I did with my 90, but my impatience has left the bike in pieces. BTW your bike rules! Don't let it go to pieces unless you are absolutely sure

Yeah I figured rings. I have a hone tool.

It is taking about 10 or more kicks to start when cold. I was thinking compression or points, but I haven't taken the flywheel off yet (see other thread)

Otherwise it seems to be running fairly well. Just not tip top.

I would think points and condenser if you had no spark, but since you can get it going, I would not worry too much. But! it would be good to get in there and file the points some.

I was lucky to get some from Scooters Originali a few years ago. I would think they are hardened, and they fill the groove completely.

to get your compression pressure find out your compression ratio and X by 14.5
eg 8:1 x 14.5 = 116 , 6.5:1 x 14.5 = 94.25
the 14.5 is psi and the air pressure at sea level
get it , hope it helps

I'm lost. Math was never my strong suit.

Vespa 150, VBA Year: 1959-62, 2 Port, compression ratio 6.5:1 (bore 57mm +.6mm

so, 6.5 X 14.5 = 94.25

Thanks JJ. Now I get it.