Anatomy of the Carbs

[motoman]

Gaskets may be interferring with those floats. Remove bowls leaving gasket in place, trim around inside edge of them with an x-acto knife or similar.

[XS1100 Newbie]

Ok, because you are talking float levels, and such, i have a question. I have been fighting with my carbs again for 3 weeks. I want this thing to run right before i put it up for sale. What is going on is this. I initially pulled the carbs to reset the float level, no big problem, set at 23mm. Blew through all passages again to make sure they were clean. Reassembled, and installed. 1 and 4 are flooding, so i pull them back off. Made sure that the needle moved freely, and nothing was in the seat, or on the needle. Made sure of my settings. Wet checked on the bench. Re-installed, and the same problem. Pulled them again. Weighed the floats, all even, put them in water, they all float. Sanded any burs i found on the float tangs, and used the magnifying glass to check all needles and seats. Again the same result. I ordered 4 new needle, and seats. Installed the new parts, checked float level again, wet checked on the bench, everything looks good. (yes, i did tap on the carb set to assure nothing was binding) Re-installed this morning, started, and ran fine for about three minutes, then started flooding. Have not pulled them again yet. Going to wet check on the bike running. Is there any way fuel can get into the bowl, other than through the needle and seat? I have never had this much trouble with any carbs, the cars, the xs650, the xj550, the cbr1000. What the hell is going on?

[3Phase]

8mm x 1.0mm brake bleeder screws fit the bowls and the barbs will hold the plastic tubes.

If you've already got the compression fittings or something else it's not a big deal. The brake bleeder screws are less expensive and you don't have to remove or 'waste' one end of a compression fitting.

.

[motoman]

Mack,
So as not to confuse, had no intention of ending up with those kinda' fuel level numbers. Knew I didnt have the time to pull them back off if levels were off. A short ride prior to leaving for rally, knew something was array, but THAT scoot was gonna do the 240mi. jog there and back, plus whatever come hell or high water.
Those were just the results of the errors of my ways .

BA80,
Dissapointed .......was expecting that in at least triplicate .

[mack]

So

Brant, not sure I got this straight. You set the floats at 23mm and this resulted in a static fuel level of 6mm down from the mixing chamber body, and under running idle the fuel levels dropped 1.5 mm from there?
I agree with both you and Scott that the spring tension could and probably does impact the actual fuel levels. Not an issue if all four needles were installed at the same time. Tension may degrade evenly accross all four resulting in common fuel heights.
I've never had the nerve to drop down near the 6mm mark even for a short ride. I think 3mm down at static, should be the target myself but really, it's up to each individual and how they like their plugs. I like the performance at 3mm but I prefer the look of my plugs at 4mm.Slightly rich is better than lean IMHO.
Glad you didn't hole piston, on your ride.Keep safe.

[BA80]

[motoman]

Hey Greg,

I think the term you're looking for is OXYMORON.

Brant, Gred, aside from a FLOW BENCH, Mack has been doing a lot of actual real world testing with various fuel levels....measured with the tubing while running, comparing both performance and plug appearance at the 2, 3, 4 mm marks from bowl surface. I'm sure "we" would convince him to perform the same test setting the carbs fuel levels much lower...ie. 6 or more mm's! How LOW would you say would be needed for this test Brant??? He's still collecting data from the various tests before publishing his results... so perhaps he can wait until he performs this extreme low fuel level = rich plugs test results!?

What say you Mack...are you up for it...once your hand heals and you can turn a wrench again??

T.C.

Hi T.C.
Finially got around to doing a running at idle fuel level test. As you may remember, I had done a static fuel level check just for curiosity, since bike was running EXTREMELY rich to, during, and back from the rally. Prior to, I had annaly set floats at .905(23mm). At that time, didn't bother to do a 'running' check since being pressed for time if a float change was needed.
Back from rally, just out of curiosity did a static fuel level check just before leaving for Columbus,GA. Bike was still loaded down with all the gear from rally, so had no intention at that time of removing everything for any carb removal.
That level check showed 6mm down from upper casting as I had previously stated.
I just now did a running at idle check(all gear still on bike, still haven't unloaded it). That fuel level across all four is 7.5mm.
With that, I still stand by my original posting of throttle plate positioning needed to draw the needed fuel for a given work load, and how a too low a fuel level affects EVERY funtion of the carb, etc.
The even lower running fuel level was of no surprise. The reason IS associated with the spring loaded needle.
For fuel to totally shut off, more upward pressure is need against float needle from a bit more rise in fuel level to create a bit more pressure on needle. That is the obvious reason for the levels to be checked while running to comply with the suggested 3mm down from upper casting.
As for what would be to low to create a lean cond.?
All I can attest to that is when I trailered the thing to Caly 4 summers back, I had gotten my millimeters and thirty-seconds confused using at that time a two piece slide float adjuster from an automotive re-build kit....my bad. The actual fuel levels, staticly checked(was before I used correct 'running' method) when I got back home were some 3/8" down from upper casting. Fortunately, the group riding was on a slow moving(15-20mph) mountainious road, and down PC-1 was noting over 55mph. IMO, that was the only saving grace to not having a lean cond. catostrofic failure(ventilated piston(s). The plugs were a bit grey though.......so no foul, fortunately.
That extreme low a level it still ran, even though very anemic on the upper end, and 'all over the board' at any normal running rpm.
So yes, I would say that was quite extreme to get a lean condition.
Generally speaking, IMO, a running fuel level that is a millimeter to high or too low is gonna give you either a rich or lean cond........WITHOUT changing venturi velocities enough to change slide/metering rod positioning for any real seat of the pants different feel. But I'll bet money, marbles and chalk it will affect fuel consumption and mileage. In other words, that running fuel level WILL affect that fuel idle mixture setting/ location(turns in or out).
All I know, after all the checking to verify those actual fuel levels, and the witnessing of a whole groug of XS'ers who would NEVER follow anywhere NEAR close behind, a 31.5mpg average overall over a 800mile run, that to low a feul level definitely caused it to raise slide/needle more from manifold vacuum drop....and that thing was gonna draw the fuel from where there was the least resistance........guarenteed. Proof was in the pudding.
Hoped that contributed to answereing some you and Mack's questions.

[jetmechmarty]

this is what I use. They thread right in to the bowls. I paid 69 cents for this at Canadian tire but you can get them at any hardware store. Tygon fits right on and you can push the hose right up to the base of the bowl. With these you can use your own bowls. When your done with the levels just screw in your own drain plugs.

That is exactly the data I am looking for! Thank you!

[mack]

fittings

this is what I use. They thread right in to the bowls. I paid 69 cents for this at Canadian tire but you can get them at any hardware store. Tygon fits right on and you can push the hose right up to the base of the bowl. With these you can use your own bowls. When your done with the levels just screw in your own drain plugs.

[XS1100 Newbie]

I threaded some copper tubing pcs., and just screw them in when i need them.

[jetmechmarty]

Hopefully, I'll find something simple and cheap at the hardware store. I don't know how much I'm going to mess with this bike before the XSSE. Probably not much.

[donebysunday]

What are y'all using for a bottom of the bowl fitting for the clear tubing? 1980 bowls.

I have a couple drain plugs drilled through and small hose barb soldered into to accept a clear hose.

[BA80]

Too small and the threads are wrong. I think that was for something else.

[jetmechmarty]

I think i remember someone mentioned using zerk fittings and drilling out the internals.

might be the ticket!

[GLoweVA]

I think i remember someone mentioned using zerk fittings and drilling out the internals.