Jetting Question

[Stime187]

I just rejetted my '91 GS and here's the rundown of what we're dealing with... mods wise:

- Cobra F1R Slip-On
- K&N Pod Filter
- 150 Mains / 40 Pilots / 2 #4 Washers under each slide

So I fired it up, everything ran fine, cut it off, adjusted the air/fuel screw to what I THINK is 3 turns out on each (I'm not sure I was right, the bit kept slipping off and I was having a generally difficult time) and took the bike out for a ride.

Well, the bike sounds different which is good, but it has some NASTY hesitation (especially in 1st gear) and the powerband generally just isn't smooth. It's okay if I hit from about a 7k roll but starting off it just sucks pulling up through the band. Although, when it does pull, it pulls quite hard... so all you gifted people, any idea what my deal is? How much of a difference does air/fuel tuning matter? This is the first carburetor setup and first bike I've worked on... so I'm pretty new.

Thanks for the help...

Scott

[mjm]

I just rejetted my '91 GS and...... it has some NASTY hesitation (especially in 1st gear) and the powerband generally just isn't smooth....

Is it just when you grab a handfull of throttle from low RPM or does it happen with a slower roll on as well?  If its only with a quick opening of the throttle your slides may be opening too fast, or it may be that the mix goes too rich as the slide rises.   If its both ways then your mix is off.  I would try going back to one washer (you know that they come in different thicknesses depending on the material)

[Stime187]

I just got the air/fuel to where I think it's about right (3 turns'ish out, no hang up or lug free revving) so I'm gonna go ride it and see. I'll try takin a washer off the slide if this doesn't work... thanks for the suggestion. Anyone else?

[GRU]

don't guess...that's what i did and didn't work for me....

take off the carbs and then adjust the air mix screw

[V8Pinto]

I have similar mods and 150's were too large.  I actually slowed down in the quarter mile.  140's are a bit lean and 145's a bit rich for my bike ~.15 seconds ET loss going to 145's.  Other people's bikes seem to like 150's ...  "your mileage may vary"...

[Stime187]

Okay, I adjusted the air/fuel and it runs better, but it's still obviously troubled... so now I'm thinkin the jets are too large and V8's post just furthered that thought. So what should I try now 140's?

Thanks,
Scott

[jake42]

i have the V&H full system and the K&N pod with 2 #4's under each needle.  My bike starts pulling strong just under 4 grand and pulls all the way to redline no prboblem. My issue is that if i do a slow roll on it's really hesistant up till about three grand. My solution so far has been to just blip the throttle when i'm sitting at a traffic light or stop sign.  I haven't been able to figure out what the issue is either.  I'm gonna check float levels to see if maybe the bike is starving at idle.  It's just annoying.

jake

[The Buddha]

OK Jake42 - the under 3K issue is float level... its really very picky, set both the floats equal and as they aere right now, set the one that's higher to the level of the lower one... that's a good start. However if you dont spend much time under 3K... and who does... leave the damn thing alone. The higher speed roll on... for stime187... The slide comming up too fast. Open throttle slowly and see if it does the same gasping thing, if it doesn't and only does it when opening fast... its slide rising too fast.
Now of the power issue... I dont doubt that power is lost from going too rich... 150 is too rich for max power, 145 might make the best power really. But in the coldest of winter days, 150 will still let the bike run rich... and that's the whole idea behind the rejet... rich = cool = better running when cold and easier starts and longer engine life. Rejet fpr power and it will run hotter and will make more power but that will hurt its life. How much - no idea, how much more power - no idea... but in theory... 150 is the largest you can run. 152.5 will make it harder on hot summer days. BTW if 142.5 is perfect ... your floats might be too high... 1-2 mm high I think. Floats being 2mm high is 1 jet size up. So really doen't take much to change it up with float level.
Cool.
Srinath.

[aslam]

You should be able to find a different sized screwdriver if you can't tell when adjusting the idle air screw.  It's a little tricky but you'll get the hang of it and then you won't have to worry about taking the carbs off to adjust the screw = big pain.

It's not a problem for me unless the engine is very hot  

ASLAM.

[jake42]

not too hijack to much, but after reading this post i went out and checked the float lever using hte U tube method.  Both are the same height, but are both about 2mm (maybe a little more) above the gasket line on the carb.   Would this be causing my stumbles down low.  It's really annoying if i have to put along behind traffic at low rpm's.

jake

[The Buddha]

OK 2mm is like 42.5 pilots down below 1/8 throttle, easy fix. Set it down 2mm... and try it. Up high it wont make that much difference, cos the float level in a fst moving bike is obviously far from steady. While you have leaned it some... like I said 150 is a few sizes bigger than perfect. Wont even feel any diff.
Cool.
Srinath.

[jake42]

not too sound too dumb, but if i want to set it down do i need to bend the little tang that the float needle hangs on down or up?  Down meaning when the carbs are upside down and i'm looking at the underside of the floats.

jake