Float adjustment

[nashville_bill]

Can anyone tell me how critical the float adjustment is? My #4 carb is running rich and I thought it was probably the float adjustment, but I guess not. I made a jig to test the fuel level while off the bike and all of the carbs look close and #4 looks to be right on.

The Jig:


The Levels(#1 is on the left):


Why would one carb run richer than the rest? They all have the same jets and the diaphrams apear to be OK. They are also very clean, having at least tripple cleaned with the main, pilot and needle jets removed. It starts well and runs good at all rpms but has a little fuel in the stock air cleaner box.

[Mike Hart]

Nice jig, Bill.

Fuel in the airbox? Float valves. You don't mention having them out for the triple-clean...

Have you blown into the fuel inlets to see if the float valve is closing all the way in #4? If it isn't, the fuel will overflow in that carb, perhaps more in a dynamic and non-level situation than while on the jig, accounting for that carb running rich.

Is the #4 float valve 'spring' free? Is the shape of the tip good? Does the #4 float move freely on the pin when not level?

If you switch float valves with #4 and another carb, does the problem move?

But then, you've probably already thought of those things...

Looks like you could adjust #1 and #2 a bit, #3 looks awful close, #4 looks right on.

Good luck, let us know when you find the culprit

[Ken Talbot]

When I was working on Tsunami a while back, I adjusted the floats towards lean by only about 2mm each. That took me from perpetually black plugs all across to ideal tan/grey. It also brough my mileage up from a consistent 30 to 35 mpg to a much better 45 to 50 mpg (Imp gallons, BTW) Now, just why your #4 is running rich when it looks 'leaner' than the others has me baffled. Moral of the story is that just a mm or two can make a significant difference, and getting them all as close as possible is what you're after.

[skids]

Re: Float adjustment

If the synchronization of vacuums is not correct, it can have an affect. For example if No 4 is lower vacuum pressure when compared to the others, it could run richer up to, and including, midrange.

Originally posted by nashville_bill
Can anyone tell me how critical the float adjustment is? My #4 carb is running rich and I thought it was probably the float adjustment, but I guess not.

[fusionking]

But that won't put fuel in the airbox. I say float valves.

[newmaac]

Bill, nice jig. I would like to see a side view of the jig if possible, please.
Fuel in the airbox sure sounds like Needle and seat issues. I would go with one of the earlier reccomendations and put some air pressure,(not much) to the bowl and see if that needle is properly seating.
As far as the original "rich" question goes, Is it possible that your mixture is correct, but you have a slightly weaker spark in #4??
Weirder things have happened.

Good luck,

[nashville_bill]

I didn't really take a "side view" pic because it would only show a plywood rectangle, but these should be descriptive:

The big hole in the left end is for opening the screw, in the float bowl, to let the fluid into the tube:


From the other side:


I cut the angled blocks at 25 degrees but would suggest 22 degrees:


The float valves do shut all the way and will not let gas through under pressure. I will try swapping the spark plug wires for #1 and #4 to see if it has weak spark causing the dark plug. The first pic is with a flash and #4 is on the right:


This pic is without a flash and looks more like it does to my eye:


Maybe #4 isn't that rich, but the other three are lean?

[skids]

Good point!

Originally posted by fusionking
But that won't put fuel in the airbox. I say float valves.

[Mike Hart]

Bill, white insulators aren't necessarily meaning too lean - you have carbon on the ends of the threads and part of the electrodes, so I'd say not conclusive.

While the brown insulator on #4 looks okay, the carbon buildup on the electrode says rich...

But if you still get fuel in the airbox, seems that's where you need to focus - figure that out, and you likely will have solved the whole problem.

[nashville_bill]

Mike,

When I said I had a little gas in the air filter, I meant a little. It was less than a teaspoon and I had ridden on a 95 degree hot day and parked it using the side stand. Should there be NO gas even in that situation?

[Mike Hart]

Even so, I'd say no, there should be no gas getting to the airbox, but a teaspoon, and on the sidestand... not exactly pointing to carb #4, is it? if it isn't float valve or spark, I'm stumped...

[Ken Talbot]

Looking at your set-up again, Bill, a couple of more things come to mind.....

IIRC, The manual calls for getting the plastic tube in place, and letting the engine run for a few minutes so you get a reading of the fuel level under operating conditions i.e. with a certain amount of gas flowing and the floats doing their thing. You might think about installing a short section of hose onto the bowl nipple, a t-fitting, then two more sections of hose - one going up for checking the level, the other going down to a shut-off valve so you can flow some fuel through the system. Perhaps the seemingly contradictory fuel level/richness observation is a quirk of trying to check the level without flow. For instance, if you turned on the fuel supply, the bowl should fill and the gas should rise in the tube, and the float should shut off the flow. But, if the momentum of the flow in the hose allowed the hose level to rise even the slightest amount above the level inside the bowl, there's no way to get back up the supply line past the now shut-off float valve. Does this still make any sense or am I just babbling now?

The other thing, and I'm guessing it is just an illusion, is that the level in the hoses in the first photo looks to be just about up to the bottom of the slides. Tell me that's just because you took the picture with the camera above the plane of the fuel level.

[fusionking]

Ride the CRAP out of it

Hey Ken! I for one don't think yer babbling. I believe it has to be running because you must be constantly drawing fuel. Otherwise you would have to duplicate the "draw" plus it would need to have the actual tank and octopus to get the presure the same. I guess what you would ultimately end up with is a carb flow bench and they are quite costly. Let the bike be your test equipment. Even tho it is hard to get it all off and on at least when you get it right it is already installed!!! Hey Bill just maybe the thing got a little crud on 1 needle valve for a moment and then cleared up and then maybe #4 just might have been rich at that point(grasping here) Have you put many miles on it? You said it ran good so maybe you just need to ride the crap out of it!!(my favorite cure for everything) unless you've been doin' that! Also are the float valves new or did you do the backwards drill bit thing? Just wondering.

[nashville_bill]

Well, as far as I can tell, everything is level. I got the carb bank level, and then used a laser level with a dispersing lens to place the tubing marker even with the surface between the float bowls and the screws.

The float valves were new last year and I can't make them leak with pressure. At least the lung pressure I can make. I've not had any gas on the floor or in the oil.

I drained the gas from the float bowls before removing the carbs and #4 had a little bit more then the other three. The bike had sat on the side stand for almost a week at that time. Previous to that, I did a 200 mile morning ride.

I had noticed the darker #4 plug and switched plugs with #1. After riding 200 miles, the #1 plug cleaned up and #4 darkened.

I think I will try swapping everything from #4 to #1. Everything meaning the main jets(original 110s), floats, float valves and spark plug wires. If it changes cylinders, I will start moving things back. If it doesn't, I'll look into other carb areas.

[Duster]

Bill: My XS11SF 79 was doing the same thing after rebuiling the carbs. I found two problems. One was that I had a float with a hole just big enough to sink it when fuel was flowing through and the float level on all carbs. Must of removed them 10 times adjusting them only a little at a time and making sure that they wer'nt to low. Finally got it and runs great but one carb had to be a little lower (raised float) to come out right.

Duster