Low end bog on my Ultra

I just recently installed 42 mm Keihins on my stock intake manifold with Moto reeds. I think I made a mistake on the manifold because I ported the intake to the same diameter as the Moto reeds.

It bogs off the hole and smokes terribly, seems to have little signal at lower rpms. Top end seems to be good even with out fine tuning the carbs yet. I peaked at 7240 rpm PET 2100 (spike I believe) 2 bars on gas, 80 deg. 16/20 solas, 160 psi., exh. and transfer porting, no advance.

Could the enlarged intake weaken the tract flow through the carburetor? Help....

Rich,

Did you install additional pulse lines or did you just 'T' them together? Also, opening up the intake to match the V-force reeds may cause what you described, but you should be able to tune much of that out. Did you match the manifolds to the carbs as well? Also, keep in mind that *every* boat is different, so you may need different jetting than the generic settings/jetting that Aquasports recommends.

James Crone Performance Engineering http://www.Performance-Eng.com

Yes James, I added an extra pulse line. I also matched the mating surfaces of the carb and manifold, 43mm I believe. Smoke also comes out of two of the carbs when I stop the motor. These are the first generation reeds, would I be better off replacing with the stock reeds.

You mentioned being able to tune this problem out. I was able to fully close the low speed screw and it still ran.

My experiences w/ those carbs is that the low speed jet is very cruicial. I would try a smaller low speed jet.

Don is correct. I would rejet the lows.

The first generation Delta V-Force cages/reeds are not going to last in your Ultra. I would *HIGHLY* recommend changing them to the 2's. They may already have lost their seating memory which can make tuning your carbs (especially the low speed jetting) a virtual nightmare.

I would check the jetting and drop me an e-mail with what you havea nd I can help you sort this out....

James Crone Performance Engineering http://www.Performance-Eng.com

Also, you need to forget about the top end until you get the bottom adjusted properly. If you dial your carbs for top end and then begin to dial in your bottom end, you chances for a seizure are quite high. You need to turn your highs out 3 turns and then begin the task of dialing in the bottom end. After the bottom end is clear, then you can proceed to the highs. The low speed circuitry always provides fuel. It is not an 'either or' circuitry...it is cumulative.

And what f/a setup are you using?

Well that tells me you need to put a smaller jet on the low side! What's the pop-off pressure? It may be lower then you need too.

Perry, I will not know the jetting nor the pop-off, ( to answer Laszlo's post) untill I break down the carbs, I will do this first thing tomorrow.

I broke down my carbs today, all three were the same, the highs are #115, and the lows are #110. The pop-off is 25 psi. Took it out today and no matter what I did I couldn't tune out low end bog. just smokes and loads up terribly. Although the mid is unreal, the pull is outstanding.

When I used those carbs on a sxi. My high speed jet was 128 and lows were 85. I think the low speed jet is way too big!! Those carbs do run a little bit better w/ about 20psi pop off, in my application anyway.