85 GSXR750 vm29 help

[arit]

setting my pilot screws and noted they were wound out quite a bit. Seems to be some discrepancy around what the right number of turns are?

1/2 or 1 1/2 turns? also the factory setting says 1/2 turn back? does this mean wind screws out fully then turn back 1/2 or wind in fully and 1/2 out?

 

 

I should note this bike is a Japanese domestic model so potentially different settings to UK/Euro etc?

[Jaydee]

Yeah, half a turn out. Turn the mixture screws in (clockwise) till they are LIGHTLY seated and turn back out half a turn. 

Edited April 5, 2020 by Jaydee

[Jaydee]

1 hour ago, arit said:

I should note this bike is a Japanese domestic model so potentially different settings to UK/Euro etc?

Doesn't make any difference as it's the slow circuit, not the mains. 

[arit]

they were wound out prob 4ish turns poss more. The reason I starting playing with the screws is it was stumbling/hesitating around 7-8000rpms and not revving cleanly to redline. With the screws at 1/2 turn it coughs and splutters down low. I'm now at 2 turns out and running better although idles high and slow to return to idle when revved

[arit]

worth noting the bike is totally stock airbox/exhaust etc...

[Jaydee]

15 minutes ago, arit said:

The reason I starting playing with the screws is it was stumbling/hesitating around 7-8000rpms

The mixture screws are for setting up the idle/slow circuit. At 7-8,000 revs the slow circuit should have well tapered off and be feed by the fuel in the main circuit. My money would be on fuel starvation from the floats set too low. Not feeding the engine enough fuel to get past 8 thou? Either that or dirty mains fuel or air jets?

Are the carbs clean and have you done the valve clearances for the best possible setting up?

[Jaydee]

Since your bike is stock, I'd try and go back to half a turn on the mixture screws. Go back to base and not have half a dozen changes to your carbs. One setting at a time, it's not a Rubics cube.  Use your choke, flatties like a warmed up engine and hate snatchy throttle action. 

[arit]

thx mate, yes I think I'll have to take the carbs off - clean/inspect

[Macduff]

my old VMs on my JDM750 had smaller idle jets than the new ones I purchased (UK Spec) though even with the larger jets it still ran crap at idle difficult to start etc. The carbs appeared clean but suspect the internal drillings were too cruddy as a swap over to another set (fitted with the new UK spec jets) worked great.  Order in a load of plasters for the skinned knuckles if your going to be regularly pulling these with a stock airbox , I ended up getting new airbox rubbers as I got sick of the hours spent cursing the old hardened ones refusing to fit in airbox and onto the carbs. 

PS it might have been the spare VMs that had smaller idle jets originally, swapped these for the new ones I had is uk size.

Edited April 6, 2020 by Macduff
faded memory