$25 jetting question

[David Wayne]

I recently changed the muffler on my street buggy from a baffled stinger to a 2 inch flow thru modified Hyabusa muffler. I came up with a lean condition on cruise, which I assume is still on the idle circuit. My current configuration is
2109, B pistons, 5.5 rods if that matters
40 x 35 heads fluffed and buffed
120 Engle
Dual HPMX Idles are 55, 140, 200 or 210 air
1 1/2 collected exhaust
10.0 CR

Am I correct in my assumptions that I need to go to a larger idle. It ran great before the exhaust change. Probably need a set of 57.5.... or 60's..... or for 25 bucks just get both. I get all my jets from Air Cooled, he contributes so much here.

[mark tucker]

I would go up to 145~ 150 on the mains., and that 1.5 exhaust is on the small side of things for that cc.

[David Wayne]

I had 150.s in the main, and it was very peppy, but was obviously too rich. The 140 mains were ok until I changed the muffler. I think I am still on the idle circuit on cruise. If I accelerate its fine, or if I gradually let the RPMs decline it ok, but it stumbles on cruise.

[modok]

info you left out
"HPMX's 40's with 32 vents, 55 idle, 135 or 145 main, 200 air
Floats at 10.5, Fuel PSI 3.5 electric pump"

2" ID muffler is too large. You want 1 3/4-1 7/8 ID, put a smaller core in it, or put a smaller tailpipe on there and see what that does.

Mark might be right, that if the header was bigger the muffler would be the right size......because...it's a ratio, but that will be for you to find out.

For jetting, 145 main 215 air? maybe.
55 idle certainly too big for webers, but perhaps empi has modified the circuits?

[David Wayne]

WOW, thanks Modok. When I changed out the stinger for a quieter muffler, I sure didn't expect it to cause such a cascade effect. As you mentioned, I guess it is for me to find out what will work.

[mark tucker]

I would leave it a little freeer flowing and add some jet.With a system that short after the collector it realy dosent have time to stagnate alot. but yes 2" a tad big for that.