110 Jets

[jiminos]

I just spent Saturday working on my carbs.... discovered (among) other things) that one of the PO's of my bike decided the air flow restriction was too much, so he punched seven holes in the bottom of the airbox bypassing the filter.... could be related to the bike running a little lean..... anyway, learning that it was a little lean and not having a stock airbox for a replacement, i thought "why not make the jump to k&n's and up the jets?"

ordered the K&N's (54mm oval), bought the jets, thinking my clymers might be right in stating that 1 and 4 were jetted with 115's and 2 & 3 were jetted with 120's, i picked up new 120's for 1 & 4 and 130's for 2 & 3.... tore the carbs down.....

guess what? 110's in all four carbs!... was there any year where that is how they came? i'm riding an SH with M34-11's. i thought they came 115/120/120/115 on the SH in 81.....

any insight? do i have carbs from a different year..... it is readily apparent they have been worked on before, but i can't tell if they are replacements or ......

[jkgrubbs]

I have an 81LH, and just got it back together. I fount that mine was, per Clymer's, to have 110-120-120-110 mains, with 42.5 pilots. I had 110 in all four carbs. I replaced with 120 across the bank, and left the 42.5's in. I am running a K&N in the stock box with a 4 into 1 Kerker. It seems to be jam up and jelly tight. I do not know if the PO monkeyed with it or not. Let us know what you do and how it turns out.

[TopCatGr58]

Hey there Jim,

I, too, had the 81SH, and found 110's across all four!!! I also have Indy Filters, and 4-1 Pipes, according to the jetting guide, this setup called for 3 sizes up, "Said 4 but to minus 1". I put 117.5's in with same 42.5 Pilots, and it has decent light color on the plugs, and full range of power to redline, no faltering or stuttering that I can notice!!

Good luck. T.C. XS81SH "Godzilla" 1179cc SuperRat

[schpiff]

Same here....110's on all..PO bought it new and swears that nothing was changed. 81 xs1100sh

[jiminos]

do i detect a pattern hewre?

hmmmmm...... interesting. seems i am not the only one to discover clymer's is just a tad off on their carb specs... or is it just our SH's?.... anyway, i am leaving the pilots as they are, going with indy's, 120-130-130-120, and as i can afford, Kerker 4-2's. I will keep you all posted with the progress through the steps....

in the interim, i have already changed the jets to 120-130-130-120. i have pulled the air box and filter, grabbed some hose clamps and some UNI filter foam, clamped the foam to the mani's and went for a ride.... i got more power than i can shake a stick at and (as bad as the set up is) it is running better than before i did the work.... anxious to pick up the indy's this week.

still lean but i think the indy's will go some toward correcting that.... vacuum guages? we don't need no stinkin' vacuum guages....

[nashville_bill]

My SH has the 110's also and came with 42.5 pilots. I have a K&N filter in the stock air box and changed the pilots to 45's. I tried 115 mains but put the 110's back in because it was to rich with dark plugs.

[jiminos]

well..... the idle mix screws were way off (thank you PO). But i got that adjusted. Bike idles great and i can blip it up to 3000 to 3500 and it returns to idle just like it is supposed to. But now... if i blip it to 4000 or above.... it hangs..... still too lean on the high end.... talked it over with some mechs in centralia (closest town with a cycle shop).... decided to get a stage three kit for the carbs..... (recommended when you got indies and stock or slightly modified exhaust) ... we shall see...

tha saga continues....

[TopCatGr58]

Hey there Jim,

The old format for 110-120-120-110 was to provide a slightly richer mix for the central carbs to reduce heat buildup since they don't get as much cooling effect as the outward cylinders. But from what we've seen here with many people reporting the same across all 4, that apparently Yamaha felt the temp differential wasn't critical!!! And with yours now unbalanced 120-130-130-120, that might contribute to the hang time above 4k. I've read that if the carbs aren't fairly closely synched, that it can cause them to hang.

I cleaned mine(81SH) 2 years ago, did the eyeball synch, set the floats with a guage, and put them on, NEVER did do a vacuum synch! With my 4-1 pipes and Indy filters, running only 117.5's mains across, it revs to 8k and back just fine, no hang whatsoever.

Are your vacuum slides sliding, did you check to see if any of them acted like they had any pinholes in them, by pushing them up to max travel, covering the curved slot at the top of the intake of the carb with your finger, and see if they stayed up, or at least very slowly dropped down. If they drop quickly, then you have holes in your diaphragms and you'll need to get them fixed before any other fancy rejetting and such. I wouldn't spend my $$ on a Stage III kit, IMHO!! Also, check to make sure you don't have any other possible vacuum leaks, the caps on the intake manifolds, the line to the Octy, the vacuum advance/retard!!
Good Luck. T.C.

[Ken Talbot]

I'd go with TC on this one - hold off on the Stage 3 kit until you find out why the carbs are hanging. Find that problem, get it fixed, then ride it for a while to see if you still think you need the kit.

[jkgrubbs]

I echo the feelings of Ken and TC. I spent the cash on the dynojet kit, put the jets in, but failed on the needles because the screws at the bottom of three of the sliders wallowed out. Because I did not want to break it worse that it was when I started, I held off on drilling the hole in the slider. I went ahead a tried the jetting, based on stage 1 indirections, and wound up spending $6 on the 120 jets, based on the jetting formulas, and one guy that is a local vintage UJM expert. I am happy with the results. I should have spent the $ on shocks/fork springs.

[jiminos]

thanks for all the responses, folks. By the time I read this, I'd aleady ordered the kit. It will be here tomorrow (7 May 03). But I will check the slides and diaphragms again. All seemed well before.

I also heard the 110-120-120-110 set up was to compensate for heat resolution issues. But it does appear that Yam felt it was not critical. I can't believe that many owners would have arbitrarily switched from that set up to 110's across the board. It had to have been a Yam decision.

Also... the needles in my carbs are of a one-position, non adjustable type. I see in clymers that an adjustment can be made by moving a snap-ring type clip up or down in the three grooves on the needle. I spent a little time looking for those grooves. They just aren't there. Obviously, there is more than one type of needle out there.

Anyway... I will keep you all posted on my progress here.

Thanx again for the input and the help.

[jiminos]

stage three kit came in.... installed it.
made all the difference in the world. # 3 carb is still lean at idle but other than that, it runs great .... so far.....
the installation replaced the needles with 5 position adjustable needles (originals single position non-adjustable), drilled out the slide vent holes, replaced main jets with 138's in all four (from 120-130-130-120), replaced primaries with 190 (up from 185's), and set idle mix screws at 4 turns out (factory setting 1 and 1/4 out).... I even called dynojet to confirm all this. they guy i talked to confirmed all the changes.... and the bike is running very well. gonna go for a 30 or 40 miler tonight to check it out...... but it looks good so far.

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