floats problem - help!

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naughtyG

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ok so today I checked that I had good spark on my #1 cylinder, and it's definitely a very bright one with the COPs!

I then went on to check out the wet floats level as I'd only ever set them dry on the bench when I rebuilt my carbs last year.

I took a piece of clear tubing that fitted perfectly over the drain hoses and marked a line exactly 16mm from its end:
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Made sure the carbs were level according to service manual, and then warmed up the motor and checked wet levels. This is what I found out:

#1 lean by about 1mm
#2 rich by over 3mm :ummm:
#3 bang on 16mm :eusa_dance:
#4 rich by 3mm :ummm::ummm:

So I took the carbs off to check it all out - I could not believe the front carbs fuel levels to be so high?

Upon opening the fuel bowls this is what I found - definitely getting a new fuel filter but it's looking like my tank may be a little rusty inside :bang head:
P1080549.jpg


looking at the float level of carb #2 on the bench, it looks pretty much right, so I really can't work out why it would show 3mm high (rich) when wet!?
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then checking #4 the same is true:
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So what now? Do I really want to bend the #2 & #4 tabs to make the floats a whole 3mm lower??:ummm: It doesn't seem to make any sense, and I'm 100% sure I held up the clear tubing's end to the middle piston mark on the carb bodies as per the service manual. How could #2 & #4 show up a whole 3mm high when they look like this on the bench? Could it be that the tiny spring in the needle valves has gone weak? On the bench those springs are uncompressed - the float is resting at the point where the needle valve closes, which is where the reading should be taken, right? Any advice will be greatly appreciated! :confused2:

Then looking a the fuel taken when draining the bowls, I also saw this:
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So I think my problem is mostly due to contaminated fuel. Does everyone agree? Still, I can't work out why I keep losing just one cylinder (apparently #1) when the bike gets really hot, and then only at idle to mid revs, then it comes back to life. Any suggestions? I really wanna get this sorted to go ride Deal's Gap next week!
 
G, I'm thinking it might be your float is binding or a leaky needle valve. How does the float move? Does it bind at all? Is the float post straight?

Yeah, fuel looks to be not the best. What I do is drain the bowls every once in awhile to check fuel condition. It might be that your filter above the needle valve are dirty or a fuel line after the fuel filter is degrading too. Try emptying a bit of fuel into a small container by removing hose from the carb rack and turning on the key. See how the fuel looks.
 
G, I'm thinking it might be your float is binding or a leaky needle valve. How does the float move? Does it bind at all? Is the float post straight?

Yeah, fuel looks to be not the best. What I do is drain the bowls every once in awhile to check fuel condition. It might be that your filter above the needle valve are dirty or a fuel line after the fuel filter is degrading too. Try emptying a bit of fuel into a small container by removing hose from the carb rack and turning on the key. See how the fuel looks.

Hey Mark,

I think the posts are all straight. I did notice a little binding, but only when the float is all the way to the bottom, which is normal, right? It wouldn't / couldn't stay there once fuel is pushing it up, could it?

I inspected the needle valves with a magnifying glass and am happy they are in good condition still. I also sprayed them with carb cleaner and blew them dry.

What do you mean by the 'filter above the needle valve'? The only filter is the one between the tank and the fuel pump, right? I'm thinking I'm going to replace the fuel hoses all the way from tank to carbs as it's inexpensive, and take the fuel pump apart to check it as well as drain and check my fuel tank. Wish I hadn't just filled it :bang head:

Anyone got any idea about my 3mm too high wet float levels readings on carbs #2 & 4?
 
isn't carb cleaner bad for the rubber boots on the needle valve?
 
I use brake and parts cleaner when working on the carbs here.

Sean
 
isn't carb cleaner bad for the rubber boots on the needle valve?

It's bad if you soak the rubber in it for a while as it will eat it, but I think it's ok for a quick spray and blow dry. I was more spraying at the yellow gunk on the metal parts than at the rubber tip.

Still wondering what to do about that 13mm wet level reading on the front carbs, anyone got any idea? Should I just get new needle valves and see if that helps? :ummm:
 
were your needle valves stock or new when u rebuilt last yr?
 
having only had the bike for one of its 23 years it's hard to tell, but I didn't renew them last year as they looked perfectly fine under a magnifying glass to me. I guess the wee springs inside their nipples could go weak over time, possibly explaining the much higher fuel levels in the front bowls. Then again, why only the fronts and not the back ones?
 
NG, any chance your floats are soaking up some gas and dropping into the bowl and needing more fuel in the bowl to lift them up? I've seen that happen with plastic floats and once with a brass float too. The brass one had a tiny hole in it. Plastic ones also had pinholes or where porous and old. Try swapping the #1 and #3 with 2 & 4 and see if the high wet level moves to the other two carbs, time consuming but cheap diagnostic otherwise.
Good luck,
Paul
 
I do have a couple of spare floats if needed. Good idea Firewrench.
 
This sounds like an idea! I'm gonna try dropping all 4 floats in gas tomorrow, if any start sinking I guess I'll have my answer..
In case I need one or more, lemme know what you want Mark and I'll pay for Express Mail - I so wanna do Deal's Gap with Robert!
 
This sounds like an idea! I'm gonna try dropping all 4 floats in gas tomorrow, if any start sinking I guess I'll have my answer..
In case I need one or more, lemme know what you want Mark and I'll pay for Express Mail - I so wanna do Deal's Gap with Robert!

They may not 'sink' G...force them below the surface and hold them there for awhile....an hour if you can rig something up...then pull them out, dry off and shake them...you'll hear any fuel inside.
 
OK. So today I went at it again.

- I soaked the #2 & 4 floats in gas for over an hour (holding them submersed with screw drivers), and when I took them out they were still floating normally, I could not hear anything inside shaking them, there were no bubbles coming up while in gas, and nothing coming out of them once out. So I have to assume they are ok - no pinholes or anything.

- I bent their tabs very slightly to make 'em a wee bit leaner, and re-assembled.

- I took the fuel pump apart, everything was fine in there, it was even clean, none of the rust particles there! :confused2:

- I took off all the fuel lines, checked them and blew them, they're all clean and in good condition.

- I drained my fuel tank, took a good look inside, and it does indeed look a little rusty in there, bugger..:bang head: Think I'm gonna swap it when I do the motor mounts with my spare one, which I believe is rust-free.

- got everything back together, but run out of time and had to go to work. On my way I picked up one of those clear glass fuel filters, will fit it tomorrow and see what happens.
I'll recheck the float levels wet and see what they show - on the bench they're all spot on.

Wish me luck...
 
so I fitted the new clear fuel filter today, fired her up, warmed up the motor, checked wet float levels (all within spec 16 +-1mm) and then sync'd the carbs.

Ran fine on idle, so I took her for a quick ride. While waiting at traffic lights, idle suddenly started to drop to 750rpm so I knew it was doing it again :bang head::bang head:

Also, I noticed that after running for a while, if I turn it off and let it sit for a couple of minutes, when I turn it on again the fuel pump clicks a lot - that means fuel has drained from one or more bowls, right? How does the pump know how to click or not? After riding it, it didn't do that anymore..

I guess it's gonna be intermittent until I replace or treat my tank :damn angry: It must be the fine rust dust that's obviously going right through the new clear fuel filter and stopping the needle valves from shutting properly - only explanation that makes sense to me, unless anyone has a better one :ummm:
 
G, have you tried putting stock coils back on to rule out ignition?
 
I haven't as I sold my originals. I may try the ones from the spare bike, but what a bitch sticking the front ones back on :bang head:

I do have two sets of COPs though, and I'm now running the second set, so that should rule those guys out, right? :confused2:

Only other thing is to try the TCI box from the spare bike - I need to remove it first..

It does make sense that if there's rust dust in the fuel, it would randomly stop the needle valves from sealing, then fuel goes into the cylinder and floods it, preventing spark, right?
 
rules out the COPs being defective, not that your vmax doesn't like them for some reason?
 
It's been running great with them on since I fitted them, which was in November last year.

This problem only started over this summer, and my bike sat a lot (mid may to early july) so I think it's the tank rust. When I did my carbs job last year there was no rust in the fuel.

Also the way it bogs down and loses at low revs then recovers at high revs is consistent with flooding, wouldn't you say? Of course it could be the TCI crapping out when hot, or a dodgy connection. I'm gonna unplug TBoost completely too to make sure it's not that.
 

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