Carb jetting

clinton · 2026-02-10T18:37:13-0700

I have a mk2a , plastic airbox and blackcaps .bike runs out of breath at 45000rpm .jet size is 22 . Should I go up or down ?

concours · 2026-02-10T19:26:43-0700

clinton said:
I have a mk2a , plastic airbox and blackcaps .bike runs out of breath at 45000rpm .jet size is 22 . Should I go up or down ?

Your problem is obvious.

Revving to 45000rpm is asking too much. Upshifting at 43000 is a better way to use the available tork.

marshg246 · 2026-02-10T20:12:39-0700

clinton said:
I have a mk2a , plastic airbox and blackcaps .bike runs out of breath at 45000rpm .jet size is 22 . Should I go up or down ?

What jet are you talking about - there is no 22. If you mean 220, then that is correct or 230 is listed some places. If you mean 4500 RPM, that has nothing to do with the main jet. How many RPMS at 1/2 throttle in 3rd gear?

L.A.B. · 2026-02-11T02:27:05-0700

clinton said:
plastic airbox and blackcaps

Does it still have the balance pipe exhaust as I've heard black caps need it to work properly although I'm not sure how accurate that is, that's if the black caps aren't breaking up internally. Probably better to fit a pair of peashooters and likely 260 main jets.
Those foam black airbox filters break up so is it reasonably new or still in good condition?

kommando · 2026-02-11T03:14:49-0700

If you have filled the oil tank to the top mark on the dipstick then excess oil will be breathed into the air filter and block the foam filter. Only ever fill to 1/2 way between the two marks on the dipstick. The foam filter breaks up over time and best to fit a new one.

clinton · 2026-02-11T07:31:08-0700

L.A.B. said:
Does it still have the balance pipe exhaust as I've heard black caps need it to work properly although I'm not sure how accurate that is, that's if the black caps aren't breaking up internally. Probably better to fit a pair of peashooters and likely 260 main jets.
Those foam black airbox filters break up so is it reasonably new or still in good condition?

Has balance tube on exhaust , everything is in good condition and it ran well with peashooters.i have just fitted black caps oem in good nick

kommando · 2026-02-11T07:48:42-0700

So do you have 220 main or 260 main jets fitted, with peashooters the best setup is 260 so if they are left in you will be too rich. Also did you change the needle jet position as I raised mine one notch when jetting for peashooters.

Fast Eddie · 2026-02-11T09:14:21-0700

kommando said:
So do you have 220 main or 260 main jets fitted, with peashooters the best setup is 260 so if they are left in you will be too rich. Also did you change the needle jet position as I raised mine one notch when jetting for peashooters.

What number slides do you use ?

kommando · 2026-02-11T09:17:05-0700

Fast Eddie said:
What number slides do you use ?

The ones in there, which have not seen the light of day for many years. If wrong that only affects the transition from pilot circuit to main circuit ie bottom 1/4 throttle opening.

ashman · 2026-02-11T15:05:57-0700

Seems like no maintenance has been done to your carbs, changing mufflers the carbs need to be tuned part of tuning is jets, needle positions, a good clean out as well, depends on the mileage jets do wear out from vibrations.
Open pipes bigger jets, restricted pipes smaller jets, but each bike is different, just got to tune till you find the sweet spot for your riding style.

Carb jetting

clinton

concours

marshg246

L.A.B.

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kommando

clinton

kommando

Fast Eddie

kommando

ashman

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