Idle jet rubber plugs removed ? ? ?

[donebysunday]

Hi XSIVES !

VERY SLOW TO WARM UP 81 XS1100LH, open the float bowls and no rubber plugs on the pilot jets ? ? ?
Only heard of this once before on the XS650 list were Blaine Hoops was experimenting with plugging the passage from the mains to the pilots with a drop of super glue and leaving the rubber plugs off the pilot jet tunnel.
He said it ran odd that way and dissolved the super glue with acetone and put the plugs back in.
I can't even tell you what I'm going through on my XS1100. Some one the P.O. had work on the bike really messed up the carbs. They blocked off the main to pilot passage, I think I'm going to have to drill through the carbs idle jet housing to open up the passage to the main as these 81 carbs are 34s just like the 650 and are supposed to feed from the main jets but are not doing this so they left the plugs on the idle jets out of the carbs trying to get the pilots to feed from the bowls by themselves by raising the fuel level in the float bowls.
Oh my Goodness what were they thinking ? ? ? ?
Don };~)

[mnxs11]

Should not have plugs

If there is no holes between it was made with no plugs from the factory.
They switched in 1980 sometime mid year if you do a search you will find more info.
I found this out with my 2 1980 h one has plugs one does not

[TopCatGr58]

Hey Done,

Just so you can see another confirmation, the 80-81 carbs were made different, there is NO sharing tunnel between the pilot and main jet towers. The Pilot jet feeds directly from the float bowl. The Main jets were resized much smaller since they didn't need to feed the pilots, that's why they are in the 110-120 range instead of the 135+ range. The float height is also set around 23mm instead of the 25.7 mm level.

These machines are cold natured, but if you haven't done a thorough cleaning of the carbs, especially the pilot circuit, then you may not be getting enough fuel thru it to help it fire and run. Also the float bowl has a JET pressed into it, for the choke/Enrichener circuit, and if it's clogged, it will make starting and running when cold very difficult as well! Have you seen and reviewed the Carbs 101 tech tip/thread?

T.C.

[natemoen]

As TC said, the '81 carbs DO NOT have the passage between the main jet and pilot jet tunnel. Since there is no passage you cannot use the plug and should not try to drill a passage.

If you need some help, let me know. I live just a few miles away in Pewaukee.

[DGXSER]

I was in New Berlin once, many years ago. Senior Engineering I think was the place, made heat exchangers. Nice small town. Flew in to OshKosh, one of my still most memmorable flights.

Anyway, As another confirmation, yes, early in the 1980 model year Yamaha was using carbs that Mikuni had updated to alot of the newer configuration, but still drilled the crossover from the main jet tunnel to the pilot jet tunnel. They also used rubber plugs instead of the srews of the earlier carbs to close off the pilot jet tunnel. These may be what your familiar with seeing on the XS650.

Somewhere into the model year, Mikuni made another update and the crossover and rubber plug were eliminated. So, your carbs are fine, and you would not want to drill that port into them.

[GLoweVA]

My G has plugs, while my SG does not.
So yes, the 80's were a mixed bag of carbs.

Strange enough though, my G which has the crossover port, still has the stock jets (110/115 I think) instead of the larger 135+ ones.
I suppose the idle circuit doesn't pull that much more fuel thru the main jet when at lower RPMs due to the main needle being down. (ie the diaphram hasn't pulled it up yet.) Once the mains open up, then the idle circuit doesn't really pull that much compared to what the mains are pulling.

Just my rambling thoughts.

[DGXSER]

George,

I have always wondered about the jetting of those "bastardized" carbs. The only set I have run into was on a fellow XSives bike that a few of us worked on over several sessions. Unfortunately, by the time we got down to the carbs (it needed engine replacement, then the replacement engine needed a valve replaced) the owner had a mishap with another bike he was working on and burned up both bikes and his house. So we never got the jetting sorted out.

It has been suggested that they jet the same as the other new styles with the same float bowl setting of 23 mm. However, it seems it would need a larger main jet to pull the fuel for both circuits the same as the older style carbs. Same thought on float settings. It would seem that they should mimic the earlier carbs. Alas, as the carbs were lost in the fire, I may never get to work on a set again.

[crazy steve]

...It has been suggested that they jet the same as the other new styles with the same float bowl setting of 23 mm. However, it seems it would need a larger main jet to pull the fuel for both circuits the same as the older style carbs. Same thought on float settings. It would seem that they should mimic the earlier carbs.

That's what I thought too, but several listers came on and said that jetting for these 'bastard' carbs is the same as all the other later types that don't have the passage/plugs. Of course, at this late date it's hard to tell if a given set of carbs is still original or has been messed with by a PO unless you're the original owner. And also leaves open the thought that the internal differences between the '78-79 and '80-81 carbs may be greater than we think or what other factors caused the change in jetting between the two types.

The manuals are silent on this which is no help, although I'll bet there was probably a service bulletin issued at the time....

[bikerphil]

All of the late type 80-81 carbs, with or without the plugs/crossover hole, use the smaller 110/120 range main jetting. Larger mains (137.5 and up) in the 79-79 carbs only. After working on countless sets of XS11 carbs, all 3 types, I am 100% sure of this.

[DGXSER]

Thanks Phil! I bet you told me that before to.

My skepticism persist only as that bike I mentioned never got running quite right, and so I never knew if the carbs were right. But I know your info comes from experience getting them running well.

[Bonz]

+1 on what GLoweVA said... My 80 SG has no passages or plugs, my 80G has passages and plugs.

80SG had 110's stock across the board, my 80G had 115/120/120/115, but the carbs had been gotten into by a p.o. along the way as evidenced by a pilot jet with a boogered screw slot, among other visible signs. However, the factory manual shows the 115/120 combo as stock.

What I have heard, and makes some sense, is the needle taper on the SG and G versions are different. Thus the 115/120 combo to help keep things running cooler/a tad richer at continuous higher speeds the Standard was predicted to see from a touring standpoint, where the needles would be lifted for extended periods of time.

[motoman]

+1 on what GLoweVA said... My 80 SG has no passages or plugs, my 80G has passages and plugs.

80SG had 110's stock across the board, my 80G had 115/120/120/115, but the carbs had been gotten into by a p.o. along the way as evidenced by a pilot jet with a boogered screw slot, among other visible signs. However, the factory manual shows the 115/120 combo as stock.

What I have heard, and makes some sense, is the needle taper on the SG and G versions are different. Thus the 115/120 combo to help keep things running cooler/a tad richer at continuous higher speeds the Standard was predicted to see from a touring standpoint, where the needles would be lifted for extended periods of time.

By golly................think you got it............BTW, elevation is all that's saving your butt runnin' 107.5's in that pretty red Special......elevation seems to save our 'oopppss's' in alot of cases...............DAHIK.......advantage, learn from it without catastropic failure.....disadvantage, seat of the pants power loss in the nose-bleed section.

[donebysunday]

81 LH Carbs without plugs in the pilot tunnels, 110 mains

THANK YOU EVERYONE !!!!!

You all helped me step back and re-think on these carbs.

Since Nathan is the closest and I think I can ride this bike maybe we could meet this weekend sometime, it's going to be in the 50s and I ride with the sun above 20s.

Nathan call me or email me, Ph.# 414 771 9534, email dsundby@wi.rr.com please.

Thank You ! Don };~)

[fredintoon]

Hi XSIVES !
VERY SLOW TO WARM UP 81 XS1100LH, open the float bowls and no rubber plugs on the pilot jets ? ? ? - - -

>
Hi Don and welcome,
whole bunch of responses before I noticed they'd let you in.
So now you know all about XS11 carbs.
Except for cleaning them. There's twice as many carbs as on an XS650 so you have to clean them four times as often, it's a square law thing.

[ExcessiveBiker]

Slow warmup

My 81SH came with no passages drilled and no plugs in the towers. This combo made a very cold blooded bike. My 81H Venturer, on the other hand, has drilled passages and plugs installed. Once the carbs were properly gone through, this bike starts and runs well when cold, using minimal starter jet. This bike ran like a Swiss watch for 60,000 miles, except for cracked coils and on TCI change.
I have the opinion the fuel going through the mains on plugged models, for the idle circuit is totally inconsequential to the overall operation of these carbs. Very shortly after the butterflies crack open, the idle ports are basically non-existant, as far as fuel flow is concerned.
Either variety can, with a little care, be tuned to run properly.

good luck and Merry Christmas to all,

ExcessiveBiker