Carb tweeks

[wraith]

Ok, had to move the Hellcat (house move) so took the opportunity to go for a test ride (on a private road of course). 

The bike seems to run fine apart from a slight burble/stutter when riding at a constant 3.5 to 4 rpm (not a flat spot) 

As all my books etc are in storage and the grey matter is not 100% sure, is this ritch or lean? And should I look at needles or pilot jets? 

For when I need a bit of down time for house 

B12 engine, with ported head, gsxr cams, open exhaust gsxr750 38mm carbs set at 150 main jets, needles in center grove, pilot jets at 3 turns out, k&n filters.

[Buzuki]

After constant ride at 3,5-4000 rpm remove and visually check the faces of the spark plugs , if the faces are black and greasy than your carbs runs rich , and opposite if the spark plugs faces are dry and almost grey to white than your carbs runs lean .

[wraith]

1 hour ago, Buzuki said:

After constant ride at 3,5-4000 rpm remove and visually check the faces of the spark plugs , if the faces are black and greasy than your carbs runs rich , and opposite if the spark plugs faces are dry and almost grey to white than your carbs runs lean .

So, which to adjust, the needles or pilots? 

As it's just on that part of the revs where they swap over. Or just try one then the other, which is my normal way 

I'm thinking the needles, as it runs great below 3000 rpm and over 5000 rpm runs great 

[clivegto]

It's a weird one I think, I've never been able to get rid of the slight miss on the Turbo Scratcher at around 3500 revs but it can be ridden round by dropping a gear or accelerating through it and it's been on 4 different dynos. I know @Allspeedshad the same problem on his gsxr Turbo and he's got his own Dyno. Yours isn't a Turbo I know but it's the same rev area that its doing it.

[Buzuki]

47 minutes ago, wraith said:

So, which to adjust, the needles or pilots? 

As it's just on that part of the revs where they swap over. Or just try one then the other, which is my normal way 

I'm thinking the needles, as it runs great below 3000 rpm and over 5000 rpm runs great 

First Pilots and not needles , leave needles in the central groove , check the spark plugs faces color than play with bigger or smaller size of the pilot jets ,

any way also check for those O-rings condition which are hidden behind any carbs intake rubber boots , if those O-rings are bad false vacuum leaking can occur  causing nonlinear gas (acceleration) response  and uneven operation on idle gas .

[wraith]

O rings are new and installed when I built the engine not long ago. 

Thanks for the info 

[wraith]

32 minutes ago, clivegto said:

It's a weird one I think, I've never been able to get rid of the slight miss on the Turbo Scratcher at around 3500 revs but it can be ridden round by dropping a gear or accelerating through it and it's been on 4 different dynos. I know @Allspeedshad the same problem on his gsxr Turbo and he's got his own Dyno. Yours isn't a Turbo I know but it's the same rev area that its doing it.

Yes can ride with it, revs all the way through with no problems and no stutters or flat spots  and when riding at 3.500 - 4000 rpm it just has this small burble. When you open the throttle it just revs straight through  all in all very happy with it.

Don't know how much time I will get to have a play with it as 1. Getting into the new place and 2. The nice weather is here and will want to just ride the other bikes as much as I can 

Thanks for the info 

[TonyGee]

my GSX11 was doing the same thing wraith, I weakened the mixture on the screws half a turn and its almost gone, doesn't effect the ride and rev's right through with no issues. I could mess with the jets or needles but it doesn't bother me.  just a tad rich.