XS11 Jetting

[maddog1]

I'm working on an 80 XS1100. It has pod filters and the rest
is stock.

I'm wondering if I should increase the pilot jet size to compensate
for the additional air flow (Less restriction/weaker signal).

It has stock jetting at the moment 110 main 42.5 pilots. Any
input would be appreciated.... Thx, Matt

[maddog1]

one more thing

This bike exhibits lean symptoms around 1/8 throttle.

[Winterhawk]

You might try putting a thin washer under your needle/clip.

[TopCatGr58]

Hey there Maddog,

Welcome!! Before you think about rejetting your pilots, have you tried just backing out the pilot screws on the front tops of the carbs. I think with the 80 and for sure with the 81's, Yamaha started putting brass caps over the "factory" set pilot screws, but you can drill them, screw a sheet metal screw into them, and then yank them out to gain access to your pilot/idle screws!!!!!

Also, with POD filters, it's recommended to go up on the MAINs, 1 or 2 sizes. How do your plugs look. If pristine bleach white, then you are probably too lean on your mains, and could try the 115's. You probably won't need to up your pilot jets, just adjust them to richer. I'm running both Pods, and 4-1 pipes, have 3 sizes larger Mains, still stock pilots, at about 2 turns out, runs great, was even a tad rich in the thinner mountain air last year when I had it set to 3 turns out, was bogging badly!!!
HTH?

[pgg]

Just to be confusing - another option - swap the 80' air pilots with 78' air pilots.

[skids]

I tried that once and the threads are different. You know, the holes in the side of the pilot jets have more of a metering affect than the size of the air pilot.

Originally posted by pgg
Just to be confusing - another option - swap the 80' air pilots with 78' air pilots.

[pgg]

Skids, I meant to say downsize only the air pilot jets.

[maddog1]

Originally posted by TopCatGr58
Hey there Maddog,

Welcome!! Before you think about rejetting your pilots, have you tried just backing out the pilot screws on the front tops of the carbs. I think with the 80 and for sure with the 81's, Yamaha started putting brass caps over the "factory" set pilot screws, but you can drill them, screw a sheet metal screw into them, and then yank them out to gain access to your pilot/idle screws!!!!!

Also, with POD filters, it's recommended to go up on the MAINs, 1 or 2 sizes. How do your plugs look. If pristine bleach white, then you are probably too lean on your mains, and could try the 115's. You probably won't need to up your pilot jets, just adjust them to richer. I'm running both Pods, and 4-1 pipes, have 3 sizes larger Mains, still stock pilots, at about 2 turns out, runs great, was even a tad rich in the thinner mountain air last year when I had it set to 3 turns out, was bogging badly!!!
HTH?

Yeah, I checked the airscrews. They were badly seized. I spent
3 hours getting them out. Three of them were mucked up pretty
bad as a result. (Nearest I can tell, they were about 2.5 turns out)

I ended up sanding the tops flat with a belt sander and cut new slots with a cutoff wheel in a dremel. Got them all back in where
they turn real nice and all. One of them was missing the little
rubber washer. Is that a big deal?

[pgg]

Confusion reigns. Skids and Maddog, I'm refering to pilot air jets, they're the ones facing the air filters. I assume you're refering to pilot mixture screws. Downsizing the pilot air jets gives a richer fuel mix in the pilot circuit. Skids, I'm curious - are the 80' model mixture screws non compatible with the 78' carbs? I've got 4 banks of carbs - but they're all 78' models. I assume the 80' mixture screws are different threads then?

[skids]

Yeah, I am pretty sure they are different threads, old model vs newer model carbs. Its like course vs medium threads, but same diam. I knew you were talking about the pilot air jets. I was just saying that the air to the pilot circuit is really metered twice: once at the pilot air jet (inlet of carb) and again through the six holes in the sides of the pilot jets. It seems overkill.

Originally posted by pgg
Confusion reigns. Skids and Maddog, I'm refering to pilot air jets, they're the ones facing the air filters. I assume you're refering to pilot mixture screws. Downsizing the pilot air jets gives a richer fuel mix in the pilot circuit. Skids, I'm curious - are the 80' model mixture screws non compatible with the 78' carbs? I've got 4 banks of carbs - but they're all 78' models. I assume the 80' mixture screws are different threads then?

[pgg]

Hey Skids lets get real confusing and do some real fine tuning - what about soldering up 1 or 2 of those pilot jet side holes.

[TopCatGr58]

Originally posted by maddog1


Yeah, I checked the airscrews(Pilot/idle circuit=actually metering fuel/air mixture...more turns out=richer!). They were badly seized. I spent
3 hours getting them out. Three of them were mucked up pretty
bad as a result. (Nearest I can tell, they were about 2.5 turns out)

I ended up sanding the tops flat with a belt sander and cut new slots with a cutoff wheel in a dremel. Got them all back in where
they turn real nice and all. One of them was missing the little
rubber washer. Is that a big deal?

That washer may still be in the hole, they can easily get stuck there when removing the screws. It's my understanding that the spring tension helps to keep the screws from turning/vibrating loose and loosing their setting, think the rubber washer may assist in this, or provide a better seal than just the threads of the screw to better control the flow thru the channel/circuit below!?

What's funny is that the early diagrams only show the screw, the spring, the screw cap, and that's it, these extra washers seem to have been added for the later models!?

Did you reset them to 2.5 turns out? If so, you can try 1/2 turn more increments and see how it behaves! Are your vacuum slides moving freely, not getting stuck, rubber tops in good shape, no pinholes?? Good luck. Skids is the carb guru, maybe he'll chime in again with info depending on what you try and your further symptoms!?
T.C.

[pgg]

I'm still confused. Skids, when you say you tried swapping 78' air pilots with 80' air pilots, down from 185 to 180, do you mean the air pilots were different threads also? That surprises me. I've got a tin full of mikuni air pilots, ranging from 180 to 210 and they're all the same thread.

[skids]

When I was trying to swap them out once I noticed that the turning got more resistance. I removed it to make sure and I compared the threads, touching sides, and they were different, although there isn't a lot of length to do the comparison. In fact, I think it was Blane that went ahead and screwed it in anyway (maybe it was Rick Jemison). BTW, I think my 78 carbs have 210's in them and the 81 has 180's.

Originally posted by pgg
I'm still confused. Skids, when you say you tried swapping 78' air pilots with 80' air pilots, down from 185 to 180, do you mean the air pilots were different threads also? That surprises me. I've got a tin full of mikuni air pilots, ranging from 180 to 210 and they're all the same thread.

[skids]

OK, go ahead, if you want it richer. I just buy new pilot jets if I want a change. I don't think I am skilled enough to do that, in fact, I am not very good at soldering wires together!

Originally posted by pgg
Hey Skids lets get real confusing and do some real fine tuning - what about soldering up 1 or 2 of those pilot jet side holes.