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After putting on a set of rebuilt carbs, new ignition points, setting timing/syncing carbs, new air-cut valve. the bike runs great, lots of power. But mileage all of a sudden halved after one tank of 40mpg. Plug #1 is fouling. The rest are perfect. I suppose crud stuck up the float? I drained the float bowl and tons of fuel came out. The fuel filter is new and totally pristine.

My only thought is that a tiny piece of debris made it past the filter, or washed out of the fuel pump and stuck up the float? The tank was pretty rusty, and i cleaned it out. Otherwise, maybe the fuel line off the carbs, which is original, is eroding inside? I can't pull it off the carbs on the bike -- can't get to the clamp on the hose.
 

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mag wrote:
After putting on a set of rebuilt carbs, new ignition points, setting timing/syncing carbs, new air-cut valve. the bike runs great, lots of power. But mileage all of a sudden halved after one tank of 40mpg. Plug #1 is fouling. The rest are perfect. I suppose crud stuck up the float? I drained the float bowl and tons of fuel came out. The fuel filter is new and totally pristine.

My only thought is that a tiny piece of debris made it past the filter, or washed out of the fuel pump and stuck up the float? The tank was pretty rusty, and i cleaned it out. Otherwise, maybe the fuel line off the carbs, which is original, is eroding inside? I can't pull it off the carbs on the bike -- can't get to the clamp on the hose.
Mag, that is going to be a hard problem to find without doing some surgery.

If you suspect a single carb as being a flooder & you can get to the bowl drain you might try pulling the drain plug,, then installing a fitting (a plastic one works good as it can be screwed in & will form it's own threads),, then attach a 6" piece of clear tubing & wire the open end above the carb (leave the top open). Then allow fuel to flow to that carb & see what the level is in the plastic tube. The fuel level in that tube will be exactly the same as in the carb bowl.. You might do a known good carb as a test height to see what normal level is. That should tell the story is you have a flooding problem.

I'm not sure on the 1100 but if I recall the 1000 pilot jet air & fuel jet can be reversed & fit OK but will leave a carb problem. (not sure this applies to the 1100 though)..

Twisty
 

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If I read your post right, you are on the correct track.

If your first tank after the rebuild was a 40MPG tank and then the mileage dropped way off and you are fouling a plug (Can't post a picture of the plug can you) I'd suspect a float issue. Height isn't as suspect as stuck.
 

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Thanks guys. I managed to pull the old fuel line off the carb plenum. It was original, IE with cloth exterior. I had to mangle off the old-style clamp first, then had a really hard time just getting off the line from the brass spigot. I figure this was the culprit, being so stuck on. Anyway, i hope to dislodge the debris sticking the float valve. I may have to flush the float bowl a few times. I highly doubt the float is set wrong, otherwise i wouldn't have gotten any decent mileage.
 

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mag wrote:
Thanks guys. I managed to pull the old fuel line off the carb plenum. It was original, IE with cloth exterior. I had to mangle off the old-style clamp first, then had a really hard time just getting off the line from the brass spigot. I figure this was the culprit, being so stuck on. Anyway, i hope to dislodge the debris sticking the float valve. I may have to flush the float bowl a few times. I highly doubt the float is set wrong, otherwise i wouldn't have gotten any decent mileage.
Mag, I'm not too sure you would have a piece of junk wash into the float needle or seat & stick a float. There is a very fine mesh screen in the tops of the needleseats that is there to prevent that very thing.

There was some float disintegration problems in some of those early carbs though.

Another place to look is at the pilot jet air supply piping, if that is plugged going to that problem carb it will cause the pilot circuit to go super rich.

Twisty
 

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Seems a lot better today, though it starts like it's flooded -- takes a few seconds on the starter. The #1 plug is still black, grrr.



I put a fresh fuel line on from pump to carb plenum, put a little MMO in the gas, filled it up. Put a clean plug in #1. I also took the gas cap off, removed the rubber gasket and sprayed the cap out with brake cleaner. Just went for a ride and so far my mileage has doubled (i've used half the fuel per distance as last ride. I can tell after 20 miles what's going on by watching the gauge.


While riding, I also turn the fuel petcock off/on to drain/fill float bowls. I estimate I'm about 38-40mpg now vs. 25mpg yesterday. I can't see how it would be anything but a stuck float, especially with gas just pouring out the drain hole when opened.
 

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twisty wrote:


Another place to look is at the pilot jet air supply piping, if that is plugged going to that problem carb it will cause the pilot circuit to go super rich.

Twisty


Twisty, are you referring to the vacuum line to carb #1?
 

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Apart from pulling the carb, anyone else have any thoughts, especially with everything pointing to flooding condition?
 

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I rebuilt my carbs on my 1000 and the next season had the float stick. I didn't want to remove the carbs, so I drained the float bowl, removed the air screw and filled it with spray carb cleaner. After letting it set for an hour or so, I did it again, then ran it through and it fixed the problem. Mileage went back up. Bikers behind me quit bitching about their burning eyes:cool:.
 

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Dave, i've done that trick before, also spraying through the drain screw. I'll give it a shot, literally. Thanks!
 

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Just drained the other float bowls and checked plugs for comparison. ALL of the carbs had the same volume -- about 350cc of gas, including the suspect #1. Plug #2 & 4 were a little rich looking. But plug #3 was perfect, and had the same volume of gas when drained. There's also no sign of gas in the air box anymore.

I suspect the K&N reusable air filter may be clogged from the crankcase breather hose? I put a brand new stock air filter in for comparison. Also, i turned all the mixture screws out at least another full turn, except for #3. I'll check the plugs after a ride. Methings it's not flooding.
 
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