Aerophile Jetting Question

[Wheelman-111]

Greetings:

The engine is 1987 Aero AF05E. Polini 47 piston/cylinder kit. NO porting done anywhere in the engine/cases. Running a new K&N filter on the stock carb, cleaned-up intake manifold, 0.5mm carbon reeds. New Leo Vinci 4447 exhaust.

I'm still sorting out variator/contra/clutch springs following Malossi 16/32 gear installation. Final ratio 7.83~:1

The mysterious Polini kit jet appeared and measured just a hair bigger than the genuine Keihin 88 I just acquired. I installed an 90-ish (Home-drilled) main jet last night, thinking a size bigger would be a good starting point. Jet needle is in the middle groove (of 3). I'll check the plug tonight.

It's not surging, but there's a noticeable sag in the power at half-throttle going about 30 MPH. Hard to tell if that's a gearing issue with variator upshift or if the engine's just not making good power there. I checked for acceleration after partial release from full throttle - found none. This suggests it's not too lean, despite the open filter and freer-flowing pipe.

Q: What next? Jet a size up or a size down? I have a 94 and that K88 ready.

[noiseguy]

Check that. Main jet is WOT, the needle jet is more responsible for mid-throttle response. Try raising it up a notch.

[Wheelman-111]

Greetings:

Helpful NoiseGuy suggests:

Check that. Main jet is WOT, the needle jet is more responsible for mid-throttle response. Try raising it up a notch

I assume you mean to try installing the clip in the lowest position, thus raising the needle to richen the part-throttle mixture? That's easy too!

Or by "raising it up a notch" did you mean install a bigger main jet?

[scooterwerx]

any weirdness around 30 sounds like a variator tuning issue to me...i could be mistaken however.

[noiseguy]

Yep, I meant raising the needle a bit by moving the "clip" to the lowest position.

[Wheelman-111]

Greetings:

The plug read was rich with my 90-ish jet. I left it in, but LOWERED the needle to the lowest of 3 notches to help lean part-throttle mixture and it felt better.

I'm now convinced I just need higher RPM further up in the speed range. Still watching mailbox for Taiwanese 8 and 7g rollers paid for Jan. 22nd. Also a trio of +1000 clutch springs to help launch. Almost there...