2.5k rpm cough

[Griff1977]

Evening!

As a few of you know, I've really taken to my carb fettling.

After I met up in West Midlands on the Dyno day I hatched my next plan for the carbs.

It was rich low and lean high up in revs/throttle position judged by splutter at 1/8th throttle position (rich low) and a/f being lean at high revs. So I went for #48 (from #50s) pilots and 182fr/185rr (from 180/182) mains also gone to 2.5/2.75 on mixtures. Clip on needles still rich (not moved from 5th position from blunt end).

At same time I plugged one of the front carb slider's lift holes (seemed an interesting mod, reading it from some of Hawk's posts).

Results:
I've not dyno'd it but did sync carbs and needed relatively a lot of adjustment (can't remember which way).
Bike feels smoother throughout range. No more slight judder mid range (near 1/8 throttle) and so overall v pleased. The ONLY negative is that it has developed a momentary cough at 2.5k rpm which I don't normally notice when pulling away as I slip clutch a bit at this range and so by time clutch is fully out I'm above 2.5k. Or if I'm lazy, I might be low down in revs and pulling in say 3rd/4th and revs are at 2.5k. It's a small hesitation and cough and as soon as I'm at 2.8k it's fine.

Could a small adjustment up with mixture help? As in its a bit lean at mo?

Not sure. Any thoughts appreciated.

Ta. Griff.

[VTRDark]

Did you get around to drilling the main air jets out as well depending on whether you have or not things are sounding a bit rich all over to me. If you go any richer on the fuel mixtures then you will be looking at going up a size on the pilot jet. But forget about that for now.

Clip on needles still rich (not moved from 5th position from blunt end)

Your on the leanest setting on the needles here and if you are still rich then you need to go back to the mains. Your mains IMO are too rich.

Are you sure your not getting a bit mixed up with working out if the bike feels rich or lean throughout the circuits. Sometimes what feels lean can actually be too rich.

(:-})

[Griff1977]

Did you get around to drilling the main air jets out as well Yep I did, about 2 months agodepending on whether you have or not things are sounding a bit rich all over to me. If you go any richer on the fuel mixtures then you will be looking at going up a size on the pilot jet. Ive just come down a pilot jet as it was "farting" on Dyno day-when held at a small throttle position But forget about that for now.

Clip on needles still rich (not moved from 5th position from blunt end)

Your on the leanest setting on the needles here and if you are still rich then you need to go back to the mains. Your mains IMO are too rich. Just to be sure- the clip being closest to the pointy end so 5th from blunt end - doesn't this let more fuel in? If so it's rich isn't it?

Are you sure your not getting a bit mixed up with working out if the bike feels rich or lean throughout the circuits. Sometimes what feels lean can actually be too rich.

(:-})

Cheers for response Carl. The pilots going leaner seems to have helped the splutter/farting at small throttle positions/cruise(doesn't have as much overrun pops neither).

Mmmmm? Just the cough to sort!! I have changed quite a few things last time though didn't I!! Maybe one change at a time next!! Griff.

[VTRDark]

Just to be sure- the clip being closest to the pointy end so 5th from blunt end - doesn't this let more fuel in? If so it's rich isn't it?

Oops sorry mate, I misunderstood you there. OK so you 5 away from. And yes that would be rich.

So in which case

Clip on needles still rich

are you saying the needle is on the rich setting or is running rich.

The pilots going leaner seems to have helped the splutter/farting at small throttle positions/cruise(doesn't have as much overrun pops neither).

If too lean then this can cause a bit of carb farts. Your over run pops could be your exhaust if that has a leak.

OK let me get this straight:
Mains 182fr/185rr
Needles 5th richest setting
pilots 48
A/F 2.5/2.75

Mains are big but you have the air jets drilled so they may require such large mains. Not sure. Needles defo seem way to rich to me. I would move 1 or 2 clip position on the needles and see how that feel. Does it make it better or worse. You A/F seems a little too rich as well for 48's

(:-})

[Griff1977]

Didn't have much time at weekend but I replaced my W2 exhaust clamps at lower exhaust section for W4 (fully stainless) and attached with silicon so no leaks anymore. I also tweaked down mixture. Haven't ridden it but early signs are good - starts a bit crisper & revs better. Ill ride next weekend. Ill see how it goes and will consider dropping needles down a couple of heights. Ta Carl. Griff.