1988 2pg engine mods

[TheGDFP]

Originally Posted by Morgan44

Honestly, I didn't think about "case volume". What effect do you think extra volume would have? It's almost exactly the height of the aftermarket reed cage.

Increased case volume is good for top end, if the transfers can move the extra mass of air.

But smaller volume maintains transfer velocity for good low speed running, throttle response.

I'm sure your stuffer-equipped cage (CR80?) and more direct manifold help with getting the case filled.

[Morgan44]

That's the major issue we tried to over come. I went through multiple carbs trying to find the sweet spot. I would lose the velocity needed for low to mid power. I settled on a 26 mm. Larger and I would lose velocity. I think the jug is the limiting factor after the reed cage doctoring.

[1989Marathon]

Originally Posted by TheGDFP

I'm sure your stuffer-equipped cage (CR80?) and more direct manifold help with getting the case filled.

Morgan, is that cage and stuffer off of a CR80?

[Morgan44]

It was from an 03' yamaha yz125

[1989Marathon]

What's the performance like now? What kind of motors have to left behind?

[TheGDFP]

Did you raise the exhaust and transfers? Widen exhaust? I'd agree, the jug isn't going to move enough air for a big carb, without rework. Timing was 155 ex

[Morgan44]

It's very responsive to the go pedal. It cranks faster than most. My cart is the one that doesn't get stuck in the mud holes, and can climb the tough hills. I think it's due to the quick wheel speed. It's no big block, but it hits harder than any modified stock powered cart I've ran with, old or new. Top speed is good but that wasn't what I was going for. I like the low speed snap and grunt.

[Morgan44]

all I did to the exhaust was clean up the header connection some. I then cut out the small 1/2 " outlet all the way up into the can and made it 1". I don't know if that makes sense without seeing how those cans are put together inside. I can't prove any differences made by that, but it made sense if you have seen the inside.

As goofy as it sounds, I ended up reducing the actual outlet back down to about 5/8. No science behind any of that, it just sounded and felt better.

[TheGDFP]

Originally Posted by Morgan44

all I did to the exhaust was clean up the header connection some. I then cut out the small 1/2 " outlet all the way up into the can and made it 1". I don't know if that makes sense without seeing how those cans are put together inside. I can't prove any differences made by that, but it made sense if you have seen the inside.

As goofy as it sounds, I ended up reducing the actual outlet back down to about 5/8. No science behind any of that, it just sounded and felt better.

Yep, a 1" stinger is pretty big for a mellow 244cc job, so I can see where the smaller would add snap.

[Tomwj]

Thanks for the replies everyone. I am goin to be doing the head work soon. I was also thinking about doing something with the reed and intake also and with you sharing the info I think I definitely will now. Isn't there also a bigger carb that will fit?