Fuel vapor "Spraying" from carb

[conquest87tsi]

Tonight I wanted to route the sender wire for my temp guage so I removed the tank. Then I thought I might as well remove my octy and install my inline filters while I was at it. Then I thought I might as well remove the carbs and check my float needles as I was paranoid they were leaking. Also wanted to replace my blots with stainless.

So I checked the needles and seats. All were clean. I checked float heights. Reinstalled the carbs. Installed new fuel line and filters. Started up the bike without the filters, and it wasn;t running the greatest.

I hit the throttle, and noticed fuel spraying out of the #1 carb and only the #1 carb. I have never had this happen before. Has anyone??

I did not have enought time to sync and adjust mixture tonight. Plus I didn't want to do all that work if I'm going to have to pull them again.

Do you think syncing will remedy this? Anyone know the cause?

[TopCatGr58]

Hey there,

I has some spraying when I had a carb with a stuck float so it was flooding, caught it on video when I was doing a little documenting of the vac. slide action. I think I remember Tod/Trbig posting recently about also seeing some spraying when he also did some video documentation. I can't recall exactly the following discussion and the causes for it, from valve shims needing adjusting to carb synch and such?? Perhaps they will chime in.

T.C.

[WMarshy]

Although its common to get a little fuel spray from atomization and pressure reverb it shouldnt be spraying too much. Its hard to comment on the quantity of spray without seeing a video...

My only comment is, check you float heights and or plugs. Does that cylinder run rich?

[trbig]

I had a different problem, but you might check for a pinhole in your slide diaphragm. With one finger, raise up the carb slide, and with the the other hand, cover the top big wide hole in the bell of your carb. Let the carb slide go. If it slides right down, you've probably got a hole in the diaphragm. It should take somewhere @ 5 seconds (Just a guess) or more for the slide to drop if holding that opening.

But like TC said, I'd think a stuck float or such since you said it's running poorly. Many times, when a bowl is completely drained on the older style carbs, this lets the float pin drop out too low and it can get cocked sideways, but since you removed the octy, this would let fuel run out of the carb even when turned off. Also, if you used new bowl gaskets, I've had them interfere with the float operation and had to trim them some.

[conquest87tsi]

I know the gaskets are not interfering, but I do have the floats set at 21mm. It ran great with this before, but I am thinking that this may be too high. I think the floats may sometimes be able to "bottom out" on the carb body before the needle seats. When I had them apart there was very little clearance from needle seated to end of float travel.

Guess I should have unstalled my bigger jets and raised the float level while I was at it.

[natemoen]

Sounds like a good place to start.

[DAVINCI]

Ditto what someone wrote above, I had that issue the first time i ever synched these guys after a re-build. I was synching without the airbox attached. I don't recommend this, but i was in the middle of a complete resto at the time. They were WAY out of synch and more than one of them was spitting fuel backwards. It cleared up after the synch, though.

[conquest87tsi]

I want to get the floats back to the proper 23mm height. Left them at 21mm because it ran so good there with the 110 main jets. I ordered 120 main jets before I took these donor carbs apart, thinking it had 110-115-115-110 jetting. However I now know that it has 110's all the way across. So I think that 120's may be a little high. So I guess I will have to wait until my 115's come before I can lower the floats. Or, I can lower the floats and install the 120's and see where I'm at. Just seems like a hell of a jump from 110 to 120.
With the 110's and 21mm float height I am getting greyish tan coloring on the plugs. So maybe slightly lean.

It does have aftermarket 2-1 exhuast and pod filters. The bike is a '79 special, with '80 carbs I believe on it. I damaged one of the '79 carbs, but have a replacement body, so I may just rebuild that and go that route. So many options and so little time. Just wanted to do what takes the least time for now. I can always get the '79 set squared away during the off season.

[conquest87tsi]

I going to install the 120's and get her back to 23mm and sync and see whats up. What do you guys use for a TACH? I bought a cheap digital off ebay and it goes in like 80-120rpm increments. I have used it successfully before, but used it the other day to time and it was all over the place. Wish I had something more accurate.

[TopCatGr58]

Hey again,

Okay, just to recap, you have 80 series carbs on your 79 machine with aftermarket 4-2's and Pod filters. The 80-81 series carbs and machines were jetted rather lean to begin with due to the EPA guidelines and such, so the stock 110's are rather lean anyways. I have 4-1, Pods, went to 117.5 and have light decent color, but the Dyno results showed that I could probably do a little better with another size up. So..with your mods, the 120's are probably NOT too rich, but a float height of 21mm WOULD be, so yeah, I concur with the reset to 23mm and the 120 jets.

For synch purposes the bike's tach is more than sufficient and accurate enough. For "tuning by ear", then you may want to use your aftermarket tach, it should be attached to the orange/gray wire(s) off of the ignition coils for your signal wire, then I think you have to double your values for the readout if it's for a 4-6-8 cylinder gauge.

T.C.

[conquest87tsi]

I did end up going with the 120's, and set the float height to 23mm. I did not resync yet, but it is running poorly.

I used a plug wire the last few times I sync'd. I use vacumm gauges and the digital tach. I will try the coil wires tomarro. See if the readings are a little more steady.

I do think my factory tach reads very low. My original tach('79) had a broken needle so I replaced it with one from a donor('81) and the '81 reads much lower. And lower than the digital. So I will be relying on the digital, which was similar to the old tach's readings.

[conquest87tsi]

I did find that the #1 diaphragm may have leaked or something because it was covered in fuel. No holes. Re-installed, and same thing. Fuel spraying back out of the carb. I will see Tomorrow if a good sync helps.

Thank you everyone for the words of wisdom

[natemoen]

You don't seem to be positive that you have late model carbs. Maybe we should start there and figure out what version of carbs you are using.

[conquest87tsi]

I am 100% certian that I am running late model carbs. They have the internel idle screws, Plastic floats, little hangy wire deal on the float needles, non adjustable diaphram needles, and a ridiculously located master idle adjuster.

I will have my early carbs up and running when ever I get a M5x.5 tap in the mail. I recieved a carb body from a XS11 member to replace my #3 that was damaged. He said a #1 would work. Well I guess neither of us thought about the master adjuster on that, which threads into the body and doesn't have a threaded hole on the #1 carbs. Only the #3 carb had a machined hole.

So by this weekend I will have early and late carbs.

[conquest87tsi]

Oh oh, and press in float seat, vs. threaded on the early models.

I've had them both open a few times.