G1 engine performance issues

[Rosati]

I've been reading this forum for a few months and came to a realization
that I didn't know as much about 2 strokes as I thought I did.

I've been running my cart for a month or two now and have been real
happy with the performance. I have been experiancing a few moments
of lost power but it always returns after awhile.

Recently, I posted a question about my fuel tank getting pressurized by
a few psi and thought it was the pump diaphram leaking crankcase
pressure back into the fuel line. I only have one line attached to the tank
so the pump had to be the reason.
I tore the pump down to check it. Nothing wrong in the pump.
I was wrong!. Dead wrong. here's what I realized...

If the pump is good, but not supplying enough fuel, then the pressure must
be coming from somewhere.
I decided to do another compression test today. I got 95 psi (110 last check)
with the engine warm and throttle opened.
I have blowby. Where does this blowby go? INTO the cranckcase, DUH!
So when the piston travels to BDC, it pulses the pressure to pump,
when the piston travels to TDC, it is supposed to creat a vacuum on the
pump. BUT, if the rings are not sealing (blowby) the rapid expansion of the
combustion pushes into the crankcase, there by not allowing the pump to
operate normally!

I will be ordering a top end kit today!

[TheNewGuy]

Install new crank seals while your at it.

[sho305]

That is why worn cylinder hurts power in 2 strokes more, plus they wear faster as they don't have the oil bath a 4 stroke has, and its really important you don't let any dirt get into the intake to wear it faster. Do the seals, and get the head decked near any shop can do it cheap. They have like 6:1 compression it is very low you can still run regular gas. If compression went back into the gas tank, seems like it would not get fuel and not run hardly? Also make sure you don't have a vacuum in the tank because the vent is not working, keeping fuel from flowing to the engine. Otherwise it should only be typical fumes that vent from gas but it should not make much unless it is heated and or agitated. The easy way is just take the carb line off and run into a jar, on the starter it should pump squirts out no problem. I also sanded out the exhaust port so it was smooth, then sanded a lot on the top of it to raise it just a hair maybe 1/32. Make sure you have the proper chamfer for the rings on the edge of the hole. Or you can try to put double gaskets under the cylinder and deck the top of the cylinder to raise the ports a little. This will raise the powerband to a little higher rpm. A good shop that knows 2 strokes can tell you. Don't expect miracles, but I did all that and advanced timing plus clutching and it was way faster than stock G1. I didn't move the cylinder up just the port, but that is an old sled trick to accomplish the same thing. Then look for a little larger carb for it just be really careful jetting it. Note when you raise the port you lose compression, so you have to do both.