Carb Help

[Aches n Pains]

Tearing my hair out (and there's not much there) - just can't seem to get my carbs to quit leaking. The bike runs great but leaks from number 1 and number 3 as soon as I stop. I can manage it by turning off the petcocks but I hate it when things aren't quite right.

I have a 1979 XS11 Special with Mikuni carbs. You can see it run at:
http://www.youtube.com/dougextra#p/u/38/_SDtJfTxt0Q

I've been through all the great postings on the site and tried most of the suggestions. Cleaned the carbs several times, set the float levels carefully (see questions below), used Scotch Brite to clean the seats for the float needles, tapped the carbs to free up the floats, etc., etc. I'm getting real good at pulling and disassembling carbs.

It's starting to feel like I need to replace the seats and float needles but at $45 each carb I am reluctant to do that without asking you guys for help one more time.

First, per the Clymer's manual and several postings on the site I am setting the floats at 25.7mm. Is that correct?

Second, if I set the float a mm high (26.7) that will shut off gas flow earlier - is that correct or have I got it backwards? I understand that would create other issues but I just want to check my logic.

Third, any other suggestions would be greatly appreciated.

Thanks so much for any thoughts,

Aches n Pains (Doug)

[natemoen]

I am guessing the you scratched or did something to the float needles or seats and they need to be replaced. I know you can get them cheaper than 45 a pop. Someone else I am sure will have a link to a site. Or you can check out Georgefix on ebay. He is usually pretty cheap. You could also change out to the later year viton float needles, they seal better I guess.

Yes stock needle setting is 25.7 +/- 1mm. If you raise it to 26.7 it will close the fuel off the fuel supply sooner but usually will then cause you to run leaner.

I say change out the needles amd seats.

[yamtom]

georgefix yes but check floats n gaskets too

Hi,

As to your last Q, if youre setting the floats with the carbs turned upside down, as usual, a higher float height will shut off the fuel sooner.

Georgefix should have needles and seats cheaper than what you quoted. I have personally used his stuff twice with very good results. I think that you can get the most basic kits which would include orings , needles n seats , and bowl gaskets from him for under 45 for all four.

There is another possibility, although its a long shot. Some have reported that plastic floats can have casting flash on them, that may hang them up on the bowl gaskets. Another reported that the bowl gasket itself may be a skosh too big, and interfere with the float motion. I have personally trimmed my plastic floats with a file and gaskets with a small scissors when working on them, but I didnt start out with the problem that you have, so who really knows for sure.

Another potential problem is that the floats may have a hole in them, allowing fluid into the float making it too heavy to work right. I hope this helps.

[natemoen]

I have to change the way I stated something in my previous post.

Its not the needles and seats from the newer model carbs that you can put in the older model carbs, its needles and seats for a different carb altogether. So let me correct my statement:

You could change over to the XV920 carb float needles and seats. They have a viton needle tip that seals better than the metal on metal of the 78-79 XS float seal.

georgefix sells both types and I am sure if you contacted home he could set you up with the right ones.

[SFerinTEXAS]

I'd zoom in on the floats sinking. Way back I submerged 8 floats for a couple of days and found 4 of the 8 good. The rest are fixable in my opinion for those that fix things .

Assuming you did the upside down blip burp flow test to test the seats.

[natemoen]

A fast and easy way to check for leaking floats is to boil some water then pour it on a clear container and then dunk the whole float under the water. If there is a hole you will see a steam of bubbles coming out of the hole.

[petejw]

the only way for fuel to leak at the back of the carbs
is if the needle isnt closing fully on the seat,
as nate stated, check floats for pin holes.
keep the float levels at stock,if you run them to lean
you'll create more problems.

even tho u can stop the leak by shutting the fuel off, the bike wont run properly because it will be running rich and youve always got the risk of fuel flowing into the engine.

take the carbs of the bike, drain the fuel and remove the fuel bowls,
turn the carbs upside down, now blow into one of the fuel inlet hoses,
with the floats closed u shouldnt be able to blow any air thru, if its leaking
youll be able to hear and see where its coming from, do this for the other 2 carbs.
also check the needle is sitting correctly in its seat, sometimes they can
sit crooked and leak.
hope this helps.

[Aches n Pains]

Thanks

Thanks for all the great suggestions.

I've tried most of your suggestions but will try them all again in a more systematic way.

The GeorgeFix suggestion was great. Got four rebuild kits for a total of $66. Also picked up some Fram oil filters.

Anybody know of a similar site for buying rebuild kits for KZ1000s?

Thanks,

Doug

[CatatonicBug]

Anybody know of a similar site for buying rebuild kits for KZ1000s?

Georgefix probably has the stuff for the KZ's as well, but you can also try z1enterprises.com. Just a randon selection showed they have the carb kits of at least one iteration of the KZ1000 for just over $20.

[mharrington]

Hey Aches I put new needle and seat assemblies in 2 of my 79s carbs. One carb leaked. After checking- re checking and rechecking again the float level (The bike ran perfect- just a leaking carb) I acted on a tip from this site (or maybe the yamaha triples community site.) My new replacement needle and seat assemblies utilize a metal washer that goes between the carb body and the thread in needle/seat unit. The OLD unit used a fiber/gasket type orange washer. I removed the metal washer and re used the fiber washer. No leak. One may be able to use an appropriate size rubber O ring too. Good luck!