Modern Vespa

Hi, am trying to fix up an old et4 (pre-leader) i fitted the beedspeed cdi unit bypass kit. I have a good spark now and the starter turns over as does the fan, but, still not running. The compression seems low and I am hoping that it is just a stuck valve or something. But, knowing my luck, it'll be alot worse.

Here's the thing.....I can't find, what the compression reading should be. My nephue has a compression tester, but, we don't know what the reading should be.??

I have found the compression ratio? 10.1 to 11.1 : 1

but thats not the details he needs.

Anyone have any ideas? Regards Kevin

The simple answer is here:
http://www.dansmc.com/compression_test.htm

Wikipedia has formula to work it out, but the short answer is (for 10:1 compression):
"roughly estimated in pounds per square inch (psi) as between 15 and 20 times the compression ratio, or in this case between 150 psi and 200 psi, depending on cam timing."
Good luck with it!

Thanks Harvey, i hope to post a picture diary of it. When its up and running. Thanks for your advice, Kev