I hate carbs...

[LoHo]

A'ight...last summer I rebuild my carbs with new gaskets, needles and seats, put her back together, synched her, and she ran like a bomb. Now, she is hard starting and floods #3, but only when running. It usually starts right up, then bogs down, smokes, and smells of raw gas, then stalls, and is a bear to restart. Reading other threads has led me to believe that the new needles and seats might be the problem. The new needles had the rubber tips; the old ones didn't. I'm tempted to just put the old ones back in, as they never leaked or flooded and my bike problems were vacuum advance and diaphragm-related anyway.

This is why I never tore into my carbs before...I was afraid that it would never run the same again. But if the new tipped needles are a common problem, I'll just put my old ones back in. Any brilliant insights?

[DiverRay]

LoHo, check the floats, and see if they hit the posts or sides of the bowl. If one float is off, it will keep the needle from closing. Easy way is take off the carbs, remove bowls, and rotate the carbs upside down a few times. Watch one float assembly each rotation.
Ray

[TopCatGr58]

Hey LoHo,

Your needles are probably okay, like DIverRay said, it's most likely a sticking float. Either it's not freely rotating on the shaft, or it's got a leak and not floating properly, or it's hitting the side of the bowl, etc.! But it could also be a piece of dirt/debris stuck in the needle valve seat keeping the needle from sealing properly, you got inline filters on that thing!?

I had the #2 carb leak due to a float not working right, turned out to be a slightly bent/angled float pin due to a less than optimal repair of a broken float post . Rebroke and repaired the post, the float pin was level and so was the float, and that cured the leak. I have been running the rubber/viton tipped float needles the past 5 years, aside from above, no problems with them!
T.C.

[Ken Talbot]

When you installed the new seats, did you notice the condition of the o-rings that seal the body of the seat to the body of the carb? If one accidently got left out, or got damaged when trying to install the seat, fuel can still leak past the seat even if the needle is sitting properly where it belongs.

When your petcocks are working properly, they will stop the flow of gas when the motor is not running, hence no leak. However, that bowl might be getting overfilled by the time the petcock stops the flow. When you start up, the needle will stop fuel flow through the seat, but a damaged o-ring will still let it flow around the seat.

JAT....

[Yamaniac]

(sorry LoHo, not trying to hi jack your thread)

T.C.
I just started tearing into the 79sf's carbs. #1 has a broken post (from P.O.)with no top (i don't know where the broken piece is). The float pin, however is tight as can be sitting on the broken post. I have turned the carbs over and even pulled on the pin (a little) to see if there is any play in it. There doesn't appear to be any play. Under these circumstances, what would you recommend for the broken post... leave it as is or try to JB at least all the way around the pin? OR??

Thanks in advance.
Theron

[edgo]

My 79SF has a broken post like yours Yamaniac. One side is OK and the needle just rests on the other post that has just half of the hole. Apparently the side where the pivot shaft pops into the post is good so the good side holds the shaft in place. It works like it should with no float leakage. I'm just going to leave it and see what happens.

Ed

[Yamaniac]

Edgo

Originally posted by edgo
My 79SF has a broken post like yours Yamaniac. One side is OK and the needle just rests on the other post that has just half of the hole. Apparently the side where the pivot shaft pops into the post is good so the good side holds the shaft in place. It works like it should with no float leakage. I'm just going to leave it and see what happens.

Ed

That was pretty much my thought, also, Ed. The pin condition isn't causing any float problems (I don't think).

The whole reason I took the carbs off was because I was only getting 25mpg, 2 up on the highway. Aside from some caked on crap in the bottom of the float bowls, all the jets and inside of carb look clean. The #2 intake boot between carb and cylinder was quite loose though. I speculate that much of a (vacuum?) leak has something to do with my low mpg issue.
Thanks

[2fast]

Another thing to look at with the rubber tip needles. If it has the little wire clip on it that goes around the float tang, that may be the problem. I had carbs that I rebuilt and found that the clip kept the needles from fully seating. If you have the clips on, try removing them. It will still work fine, and may cure the leakage.

[pathfinder]

Nobody said anything about rust on the needle or gunk stuck to the seat. These old gas tanks pretty much all need cleaning and derusting.
I have filters on the petcocks up inside the tank, two inline filters, and filters on the the bottom of the needle & seat. Thats a total of 3 filters that should stop any gunk before entering carbs but crap still gets thru sometimes. I am going to try the salt water and battery charger method of cleaning the tank one of these days.

[skids]

Hey LoHo, at least the petcocks seem to be working! Try flushing the float valve. Open the bowl tap, put wife's favorite sandwich tuppaware in place to catch gas, turn the appropriate petcock to the "Prime" position. You just might get lucky (I mean with your carbs).

[LoHo]

Skids, that sounds like a good first choice. I think I'll drain it to move the float, then turn it on prime to rinse it, then close the drain and see what happens. My wife's tupperware, Ray? Are you nuts? I use the crystal stemware so that I can easily check for particles.

By the way, my carbs were pretty clean, and as it turned out, the bowls/needles were not my root problem. My diaphragms had several holes, which I fixed, but my previous vacuum advance repair (my true problem) was faulty only in that I managed to reverse the wiring. That pseudo-fix left the same symptoms present which resulted in the carb rebuild. So, all of my carb woes are the result of a bonehead error in the first place.

Oh well...at least it motivated me to do a valve adjustment and carb synch...

[LoHo]

Oh yeah, Skids, I was thankful that the petcocks do their job and I don't wind up with a crankcase or garage floor full of gas. Of course, I've probably jinxed that now...thanks a lot!! ;^}

[CWilliamson]

yes be thankful they did. when I bought my bike imagine my suprise when 2.5 gallons of gasoil poured out of the oil drain hole into my 1 gal container. ugh what a mess. Inside of the engine was nice and clean thought :-)

Clark

[LoHo]

We all thought that you were just retrofitting to two-stroke...

[DiverRay]

LoHo,
Be carefull!! I have a friend who has an old 400 Husky. He had problems starting it, and I found the needle leaked, and the crank and expantion chamber were FULL of gas
And he wanted help getting it started!!
Ray