G1 engine is a J42

[mikeasis]

yes using all the parts he mentioned.

I would not have thought of the muffler being different, it makes sense though.

[mikeasis]

Originally Posted by smallblock450sl

1982, J17 engine. The bottom end is the same for all. The 82 had a differant cylinder/reed assy/carb and muffler.

Any idea what was done to change the compression on these engines? Was it all in the cylinder head or was the piston also different?

thanks
mike

[smallblock450sl]

Originally Posted by Spicyunicorn

90 shouldn't be to far off mine ran like a raped ape at 100 with the higher compression motor

Perfect numbers for a J17 engine

[smallblock450sl]

Originally Posted by mikeasis

Any idea what was done to change the compression on these engines? Was it all in the cylinder head or was the piston also different?

thanks
mike

The cylinder/can't remember if the head was differant/reed assy/manifold/carb/nut ring/ muffler and oil pump, piston was the same.

[mikeasis]

sorry not much real experience with 2 strokes but if the piston is the same wouldn't the chamber on the head would be different?? . Would the ports (port timing) change compression? the chamber on the head I think would be larger so milling it would raise the compression.

thanks for your help

mike

[sho305]

I think the porting was different. I know you can only cut that head .030 or something and you get into the chamber squish. To go more you have to cut the cylinder, especially if you want to raise the cylinder or raise ports....iirc. However I had one cut .030 and it helped. I raised the exhaust port just a tiny bit. It outran any stock cart easily. Advanced the timing also. Stock muffler not sure on airbox.