no compression after 70cc kit

[Nick16]

I have a 2000 zuma 50 and installed an udgrade 70cc big bore kit. after installing it all and checking it over i have about 1/3 the compression im suppose to have. i have spark and fuel but no compression and i need some help.

[Blackbomber]

Two questions:
Which kit did you install?
What was your compression with the old top end, and your current (low) compression?

[Robertskappasig]

I experienced a similar problem with my 150cc kit installation. My camshaft sprocket's tab that is supposed to seat into the camshaft was damaged from the factory, but worked with their installation. When I took it all apart and tried to put it back together the damage worsened and made it so the timing couldn't be set properly. I had spark and fuel, but the thing was off by a cycle. No damage, thankfully, but had to have the shop pick it up cuz I was stuck. My compression also seemed off. I spent 120 bucks having the shop figure this out, and it's the best 120 I ever spent. On anything. I pride myself as someone becoming a good wrencher, but am glad I waived my white flag when I did, I never would have caught it.

[BWSman67]

Robert,

The 2000 Zuma 50cc scooters are two strokes. No camshafts or valves.

@Nick16; did you let the engine turn over for several cycles before looking at the reading? Checking the compression after only one cycle won't give an accurate reading.
Did you put all the head gaskets on? this will lower the compression readings as you are changing the ration between the non-compressed volume & compressed volume.
Double check the rings to make sure they were installed properly.

What were the numbers you got when checking the compression.

[Nick16]

my normal compression is suppose to be 90 but i was only getting about 30 or so after several turns. im going to try and check all the gaskets and rings to make sure they are right

[Microron]

I suffered very ragged performance after my 70cc upgrade... it was quite gnaarly to start... and ran poorly with little power... After removing the cooling shroud around the cylinder, I, BLUSH, discovered that I had placed a spacer/shim gasket ( part of the 'squish' adjustmnet) 90 degrees out of place... Low compression and performance were caused crankcase compression 'blowing' out of the improperly positionned shim gasket...

I considered myself a good shade tree mechanic, but missed a very obvious blunder... I guess that makes me a better wrencher now... or maybe it's time to set-up a lemonade stand....

You might need to crawl back under a shade tree for a moment or two, and then take a fresh look at all parts of your build.

Good luck. Please let us know what resolves your problem.