porting stock garelli jug

Christopher Jones /

how many of you have done it and seen improvement, also I'm not sure where to start honestly. Ive ported sbc heads but those seem simple compared to a two stroke.

what would you suggest to do? how much to open up the ports.

Re: porting stock garelli jug

it's all a matter of timing. The port heights reflect the degree that they open/close and their duration. You can think of their heights as you would sbc cam duration. Cam overlap can't be applied, in fact less port overlap moves the hp up higher in the rpm range in a two stroke. Just like in a four stroke gas velocity has to be considered when dealing with duration. Port width can be thought of a lot like valve lift height and again this affects gas velocity. Then there's port flow direction that is how the cylinder is scavenged, which isn't really something that you can modify in a fourstroke.

There's the three two stroke bibles you need to read and then crazy wayne's posts as they apply specifically to very small two strokes.

Re: porting stock garelli jug

There's gains to be had. Garelli noi ports are already pretty gigantic to start with so what you can do without porting it into a boat anchor is somewhat limited. I've raised the exhaust by a mm and widened it by 2. I dropped the intake by .5-1mm and again widened it by 2.

I didn't really apply any science or calculations to that, I just kinda gutted it to see what would happen. it boosts top end, and with a decent pipe you don't lose much low end or pull. stock carb, decent pipe, ported, expect 35-ish with good pull.

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