330 jetting help

[pantera1975]

Last summer I ran a CEL needle on the center position and had some knocking from 1/8-a little past 1/2 throttle. It runs rough in them positions but has good top power. For needles I have on hand a DGH,cej,cckcel,ccl needles. Im in Wisconsin its fairly humid here in the summer 80 deg range and less than 1200 ft elevation. What should I try for a slow, needle and main. I have a ESR 330 trx 9 cylinder, ESR ATC 5 pipe, v-3 reeds 39 mm AS carb, stock ignition and a dome set up to run 50/50 mix VP110/91 fuel with Klotz 32-1 supertechniplate oil. I will get another needle if a different one works better. Running full air box with no lid

[rk88r]

The last letter affects 1/4-3/8 range. Try your cej. The J is a little richer than the L.

[fearlessfred]

Last summer I ran a CEL needle on the center position and had some knocking from 1/8-a little past 1/2 throttle. It runs rough in them positions but has good top power. For needles I have on hand a DGH,cej,cckcel,ccl needles. Im in Wisconsin its fairly humid here in the summer 80 deg range and less than 1200 ft elevation. What should I try for a slow, needle and main. I have a ESR 330 trx 9 cylinder, ESR ATC 5 pipe, v-3 reeds 39 mm AS carb, stock ignition and a dome set up to run 50/50 mix VP110/91 fuel with Klotz 32-1 supertechniplate oil. I will get another needle if a different one works better.

all that seems kind of odd to me, knocking would make you think that it was lean or not enough octane ,but a lean condition would cause a bog and not rough running

[rsss396]

I agree with Fred about the octane, I would go after cutting the dome for less compression. Fuel will only mask detonation so much.

[pantera1975]

the dome was made by my builder. I tried 100% race fuel last summer and didnt make much difference.

[Tbone07]

Got some plug chop pics?

[Jerry Hall]

all that seems kind of odd to me, knocking would make you think that it was lean or not enough octane ,but a lean condition would cause a bog and not rough running

Mixture than is lean enough to bog will not usually allow the engine to experience detonation because the engine is not experiencing a power stroke or a combustion event on the revolutions it bogs.

A mixture that is just rich enough to not bog may be lean enough to cause detonation.

[Jerry Hall]

The last letter affects 1/4-3/8 range. Try your cej. The J is a little richer than the L.

According to the theory presented in Keihin diagrams on fuel deliver vs throttle position. the the last letter controls fuel flow in the 1/4-3/8 range.  My experience has shown that the last letter will affect the fuel flow up to 1/2 throttle on some tapers especially on the C,D, E tapers.

The last letter will also control fuel flow all of the way to closed throttle anytime the RPM is over about 2500 RPM.

The last letter also has a larger influence on the mixture at closed throttle to about 1/4 throttle at high RPM deceleration than the pilot jet or air scrirew.

The airspeed at the needle is slow enough at an idle that the pilot jet transition holes feed the  motor the majority of its fuel at an idle.  The airspeed at the needle at high RPM and closed throttle is high enough to cause the last letter of the needle diameter to control most of the fuel flow.

[rk88r]

Good info Jerry.

[fearlessfred]

Mixture than is lean enough to bog will not usually allow the engine to experience detonation because the engine is not experiencing a power stroke or a combustion event on the revolutions it bogs.

A mixture that is just rich enough to not bog may be lean enough to cause detonation.

no argument from me ,but OP says it runs rough in these areas.knocking and running rough doesn't seem to go together unless its an electrical issue or I guess the loss in power from knocking could make it feel rough,I have never had anything that lean on the needle

[atvcrazy]

I would try the a richer all over needle and go to a "D" instead of a "c" I would try dej,dek. I know you have a little altitude and humidity during the summer but sounds like you are lean in the middle coming off the main jet and this should help.  CR 500 has the same problem with the stock cgj needle and the fix is going to a dgj,k,l needle to richer up all over the midrange

[fearlessfred]

the dome was made by my builder. I tried 100% race fuel last summer and didnt make much difference.

your builder could be of more help than us

[flynbyu]

I have the same 330 ESR top end and pipe as you, and I also run my quad at the same elevation as you. I agree with atvcrazy, try your DGH needle center clip position. That's the needle Eddie recommended to me. That's the needle I run along with a 50 pilot and a 180 main at 75 degrees.  Then do some plug chops. You can tweek it from there.