Hello and welcome. I won't claim expertise for mini motors, but I'm always suspicious of compression gauge error unless proven with a master gauge. Cylinder/piston clearances and ring gaps should also be suspect. I'm hoping our resident forum expert @Axzon has found your post and weighs in with some ideas for you

 

Hello and welcome. I won't claim expertise for mini motors, but I'm always suspicious of compression gauge error unless proven with a master gauge. Cylinder/piston clearances and ring gaps should also be suspect. I'm hoping our resident forum expert @Axzon has found your post and weighs in with some ideas for you

Hello all,

I have a 2004 Jr Adventure that I can't get started. Did a compression test and it come back low around 28-30psi. I replaced the piston and rings but still can't get the compression up. I'm not too familiar with two strokes so are there any other test I can do to see where I'm losing it?

Welcome to the forum.
Here a few things you can try:

• Check that the head gasket is in a good condition.
• Look for a crack in the cylinder head.
• Check that the muffler and/or exhaust pipe does not have something that is blocking the exhaust flow.
• Check that the reeds does not have any damage.
• Check that the two oil seals, one on each side of the crank, are not worn and compromises the compression.
• Inspect the cylinder bore for wear and grooves/damage.
• Check the exhaust pipe for damage and make sure the exhaust fumes can flow freely.
• Check that carbi is working well and the air filter is clean and oiled.

Low compression is normally a sign of wear on piston and piston rings. But can also be a worn bore.