Helppppp!! 1989 gsxr750 stock carbs wont work??

[Livharder]

89 mikuni bst36ss. Completely redone, emultion tubes done with oring under. 

Must of taken them off and on 30x times. 

Full hindle exhaust, kn pods, factory pro jet kit. Stock rebuilt top end engine(valves etc are fine) new plugs. Dynatek ecu, plug wires, igniruin pick up. Mainly stock advance.

Calibrated carbs.

Settings are: 122.5 mains, 14.5 floats, factory pro needle now last groove down, 32.5 pilots, air screw 2.5 turns out

Plugs look mainly on the lean side (why the last bottom groove on the needle)

Fu....in flat spot at 6000-7000 rpms with some hesitation and poping after it passes that seems to want to pull around 10000+ 

HELP!!!!

 

[Jaydee]

I'd guess having the e-clip on the last groove aint helping. Try putting the clip on 3rd from top and see what happens to your flat spot. It'll probably move your flat spot down the rev range where you can play around with your mixture settings  (slightly richen(?)) 

[TonyGee]

are you running with 4 separate pod filters ? some people say the 2 twin pod filters are better ????   just a thought.  

[Livharder]

47 minutes ago, Jaydee said:

I'd guess having the e-clip on the last groove aint helping. Try putting the clip on 3rd from top and see what happens to your flat spot. It'll probably move your flat spot down the rev range where you can play around with your mixture settings  (slightly richen(?)) 

Thanks but that was done originaly and it was worse. Plugs were white also

[Livharder]

1 minute ago, TonyGee said:

are you running with 4 separate pod filters ? some people say the 2 twin pod filters are better ????   just a thought.  

Yes, I Got the twin pods

[TonyGee]

maybe its time for a trip to a dyno 

[wraith]

If it flat spot is 6-7000 rpm it's the main jet you need to increase. Go up 2 sizes and see how it runs. 

Why the last groove, to lift the needles, you'd probably find that if you lowered the needles you will get it serging lower revs and when at a constant speed.

6-7000 rpm is where the main jet is taking control of the fuel from the needles.

And welcome to OSS

Edited May 22, 2022 by wraith
Add a bit

[Livharder]

1 hour ago, wraith said:

If it flat spot is 6-7000 rpm it's the main jet you need to increase. Go up 2 sizes and see how it runs. 

Why the last groove, to lift the needles, you'd probably find that if you lowered the needles you will get it serging lower revs and when at a constant speed.

6-7000 rpm is where the main jet is taking control of the fuel from the needles.

And welcome to OSS

Thanks!! Will try for sure

[Evilston3r]

I had something similar with my 1100 m , but that was 40mm carbs, I only got rid of the flat spot when I fitted an oem airbox , if I used pods or twin pods it had a really bad flat spot at 3k, and as I fucked about with jets needles ect, (carbs was completely rebuilt with oem parts, and sonic cleaned) it just moved up and down the range

[wraith]

24 minutes ago, Evilston3r said:

I had something similar with my 1100 m , but that was 40mm carbs, I only got rid of the flat spot when I fitted an oem airbox , if I used pods or twin pods it had a really bad flat spot at 3k, and as I fucked about with jets needles ect, (carbs was completely rebuilt with oem parts, and sonic cleaned) it just moved up and down the range

The 40mm carbs are renowned not to work right without the airbox.

[TonyGee]

I think most CV carbs are a P.I.T.A.  without their airbox   I remember pulling the snorkel of a B12 once and it ran like shit !!!!!  it went back on pretty sharpish.