XS1100 (BS34s) Guzzles Gas, Runs Rich

jetmechmarty

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XS1100 gets as good as 30 mpg. Plugs are black. Long history. Stock airbox. Jardine 4 into 1. Stock pilot jetting. Stock main jetting. Genuine Mikuni jets. Everything is stock and clean.

The bike starts right up. Idle is good. Acceleration from stop is good. Runs like butter all through the RPM range. It's fine riding slow or fast. I should get about 40 mpg and not be looking at black, sooty plugs.

I believe I need to tamper with fuel level. For better economy, do I need to decrease or increase the fuel level in the bowls? Whatever is wrong, is wrong across all four.

Thanks for reading this XS1100 motorcycle post.
 
If it IS the fuel level, it's high, need to raise the floats as you look at them with the carbs upside down on the bench.
Are those BS34's? check the o-rings on the float valves.
 
Lots of miles? The slide needles and their seat, also called needle jet, I think, DO wear and cause a rich condition right where you use the bike the most, right in the mid-to- lower range of RPM ................
 
pull a slide, lets see the assembly order on the jet needles,caps, springs etc..
 
Wow, that many miles it could very well be worn needle jets. We had to change them out on my buddy's R90S BMW at about 80K. Worn needle jets is a known issue on the Dellorto carbs that came on that bike. Although worn needle jets isn't a common problem or issue, it can and does happen on high mileage bikes.
 
pull a slide, lets see the assembly order on the jet needles,caps, springs etc..
Well I would want to check compression, recheck timing at idle and full advance.
bs34 needle assembly.jpg

Since it's so rich yet works OK at idle I'm with (5T) something is up with the needles (5T) wear is one possibility, check part #s, mis-assembly another. We did have a one guy had the order wrong. Things happen, confirm.
Is petcock vacuum fed from one intake?
Have you waded through this thread?
http://www.xs11.com/forum/archive/index.php?t-39799.html
Looks like some gotchas in the needle jet, main combos.
It also details the mikuni #s
 
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I'll pull a slide this evening. Yes, I'm familiar with that thread on XS11.com My jets are the stock 110 all across. I will double check the number on the needle. XJ4Ever.com has reproductions if I need them.
The vacuum shutoff is connected to the #2 intake. The vacuum advance is to a port on the #2 carburetor.

The carburetors are BS34-III 3J6-00 I need to verify needle 5GL16 is installed.

I thank you gentlemen for stepping in on this. XS11.com has mostly died off.
 
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