gsxr 750 carbs on gs 1100

[dave419]

need some jetting help ,ive put a set of gsxr 750 36mm miks on my stock top end dragbike they have 32.5 an 160 mains an its real lazy. alt around here is corr to 2500 to 3500 in summer i also plan on running pods.
bike is a car tire chasis 1,2 auto slider, dyna electrics 4000sp low auto shift falicon crank ,thanks dave

[Carter Turk]

I have some GSXR 36's on my 1150 (1229) with 32.5 142.5 mains and jet kit and pods. The head is stock as well. I think the needle is fourth down from the top and the floats had to be leaned out quite a bit. It hesitates around 3000 rpms, I think where the pilot circuit overlaps the needle and maybe the extra lean float setting might have something to do with it.

Before these changes the carbs had 160 mains and stock 30 pilots. Every plug fouled numerous times. Now it runs well aside from the 3k hesitation.

[tfb]

Carter Turk, the hesitation at around 3000rpm is something I've been through with my 1100... turned out to be one size too rich in the pilot jets, in my case. I offer the info. for what it might be worth as you sleuth through things.

Dave, your main jets sound waaaaay to large to me! Just my 2c's worth.

Keep working at it guys; the rewards of getting the jetting right are very satisfying. ;-)

Mike.

PS. Great site on the finer points of carb tuning is FactoryPro.

[Carter Turk]

Tfb,

Any ideas what your float height is? Mine is something like 17-18mm. I suppose I could try the stock pilot again and see what happens to the hesitation.

I actually tryed a Factory jet kit in these carbs, but the used carbs came with Dynojet. When I put the Factory kit in all the plugs fouled. I think the previous owner did something to them or the emulsion tubes are worn out.

The needles on both jet kits are totally different one blunt, the other tapered.

[tfb]

Sorry, I've got no idea what my float height is... which is a good prod for me, I should check the silly things.8-[ Ahem... never bothered checking them because I'm happy with the jetting, if it ain't broke don't bother fixing, etc. ...

Worn emulsion tubes are a common problem with time/use/age (mine are worn but I manage to live with it); and I might be wrong but for the life of me I can't see how them alone are going to richen the proceedings to the point that you foul plugs. It is more likely the Dynojet needles are a more suitable profile for your bike than the stock needles.

Yes, try popping in the original pilot jets. You may find that the hesitation disappears -- if so, bingo. (Question: does the hesitation get worse as the engine warms up? If so, definitely running rich at that point in the rev-range. But see the FactoryPro site, 'High RPM engines' section, for all the good tips in this department.)

[If carburettion is only a little bit out, figuring it out is relatively easy. But if confusion is setting in, go for an air-fuel ratio (AFR) on a dyno. It's not the final word on getting the jetting right (nothing like Real World conditions to get it spot-on!), but the graph tells you at a glance what to try next. And a good dyno operator will be able to give good pointers too.]

[Carter Turk]

We recently arrived in the new age with a dyno near here. I'm kinda of nervous to have it run on one. Find out my settings are way out in left field.

Regarding the needles, I was refering to the Dynojet vs. Factory needles.

The Dynojets look like a fat thumb where the Factory looks like a ladies index finger. Seems like the Factory would get better atomization where when the Dynas are raised there's no real taper to speak of.

It seems if the emulsion tubes were ovaled out from wear gas would be getting by. I read something about this being common of FZR 1000 carbs.

[tfb]

Yeah, I was nervous too about putting my bike on a dyno at first -- I mean, I didn't want to see the engine go 'POP' because the old girl couldn't hack the revs after 25 years of being caned (as is what happens to old Kat1100s...). I rarely take it past 6000rpm (no need with all that grunt) and I wondered what might happen. 8-[

But I needn't have worried. On a dyno the engine is under load at all times, and as the revs rose and that beserk howl broke loose it was awesome! :twisted:

The worst that will happen is that you get some bad news re. your jetting. But that will really be good news, because now you'll know what to work on.