Carb testing issues

[jfmerk]

So I am testing my carbs before I install them on my full 78E restoration, following the advise of many here and great advise it is! I first tested them with the bowls removed, upside down and supplied fuel to them. Lifted the floats to burb the air out, blew away the residual fuel and watched. No leaks. Let them sit for 30 minutes, no leaks. Put the bowls back on turned them right side up and supplied fuel again. This time, fuel immediately spewed out the bowl vent port between carbs 3 & 4. I lifted them up higher than the fuel supply to stop the fuel flow, set them back down slowly and the leak seemed to stop. But I have a continuous leak of one drop every 3 - 4 seconds from carb 4. So off came the bowls again to do the inverted test again after blowing out the needle seat thinking a piece of debris is preventing a seal. Now... all of the needle and seats seam to be weeping a little fuel! I bought TourMax kits, the basic one with a new needle and seat and few gaskets. Here is what I've done:

All carb bodies have been ultrasonically cleaned, all jets removed and cleaned, passages cleaned, nozzle removed and cleaned, needles and seats all replaced, float heights all set to factory height and all within .005" of each other.

The needle and seat should provide a "zero" leak seal right? Are the TourMax kits junk?

I guess my next step will be to make sure the floats don't have a pin hole?

Any other advise would be appreciated!

Here's my setup up:

[natemoen]

To check the floats for holes put the float in a glass of boiling water. If there is a hole you will see bubbles coming out of the hole. It must he boiling water though, cold warm or even hot water wont work it must be boiling (of course you must remove the water from the stove so that you can see the bubbles though).

[CatatonicBug]

I've never heard of TourMax kits, so I can't comment on them. One thing to remember is that the proper adjustment of the float height must be done with the carbs on the bike, with the engine running. It's a long, tedious process, but it should only need to be done once.

[dpotter58]

I've never heard of TourMax kits, so I can't comment on them. One thing to remember is that the proper adjustment of the float height must be done with the carbs on the bike, with the engine running. It's a long, tedious process, but it should only need to be done once.

Really? I have never seen that suggested? One of the super gurus here showed me how and we did it with the carbs off the bike. Even the tech tip dosen't suggets running on the bike. Seems like it would be a bitcch to get the bowls off with them mounted. Did you do it that way?

[CatatonicBug]

Really? I have never seen that suggested? One of the super gurus here showed me how and we did it with the carbs off the bike. Even the tech tip dosen't suggets running on the bike. Seems like it would be a bitcch to get the bowls off with them mounted. Did you do it that way?

That's how the manual tells you to do it. You don't take the bowls off with the carbs mounted - you have to take the carbs off every time (which is why the process is so tedious). The spout on the bottom of the '81 carb bowls makes this process much easier, as a piece of fuel line will slide onto it and you can see the fuel in the line, as it sits in comparison to the carb body. Some people have used pipe nipples and created their own spouts to do this. The trick is that you have to get the bike perfectly level before you start the process.

[jfmerk]

Well the carbs held tight during another round of testing and they're mounted on the bike. I brought them back to the desk and removed the bowls and floats. I gave each float a firm shake listening for any fuel swishing around inside. I thought if they are leaking that bad there must be something inside the floats(s) right? I detected nothing.

I didn't test them with boiling water, it makes sense though. I did submerse them in water perhaps to no benefit as you point out. I did try something a little radical perhaps. While I had the floats off, I used a tiny punch and a tiny hammer (hammer and carburetors don't sound good together ) and ever so gently, one little tap on each needle to get it to "seat", of course not on the spring loaded pin, just to the side. It's a trick I've used sometimes seating check balls in hydraulic valves. I'm thinking soft seat needles would seal better.

But after an hour of testing, no leaks... in both positions... at least for now. Yes the final test will be on the bike. I'm looking forward to starting it for the first time in the next few days. Thanks for the tips!

[Larrym]

Three Glitches That make you say #@@XX!!!

"The needle and seat should provide a "zero" leak seal right? Are the TourMax kits junk?"

Ummm no matter where you got the parts or what brand they are....the answer I have is "Yes". Zero tolerance for leaks. After "Blipping" the floats (Thanks Prom!!!) to get the air out of the line and real fuel at the needle/seat sealing/mating surfaces, cleaning up the fuel excess at the little "well" around the area with air...the fuel flow should be ZERO.

(That's what I got with OEM needles/seats...)

As far as what happened when you turned the carbs right-side-up with the bowls on, there's a couple standard glitches that catch folks:

1.) The little tab that stops the float from going down too far is adjusted wrong so the float falls to the bottom and then gets STUCK. (Overflow due to the needle/seat not meeting like they're s'posed to...)

2.) The edge of the float getting caught on the bowl gasket due to the gasket sticking out too far. (exacto knife to trim it off fixes that one easily...)

3.) The float shifting to one side (left or right...) as you move the bank around and then it sticks to the side/jams. (Tap it loose with a screwdriver. Don't use your beer can: danger of splashing out precious plywood aged beverage!)

Any of these three the culprit?

Seems like you're really on the track everywhere else...

[prometheus578]

Now Bug... That's for the later carbs.
He's got a 78E model. Float level is checked with the carbs offa the bike.. inverted, etc.

For the later carbs, you check the float level with the carbs on the bike, as you state. If the level is off, ya pull the carbs and adjust them. No need to place them back on the bike to test your "new" adjustment... Just pop them in a vise or prop them up level and check the adjustment again. (Throw a carpenter's level across the tops if'in ya can't position the carb bank level by eyeball)

[CatatonicBug]

Now Bug... That's for the later carbs.
He's got a 78E model. Float level is checked with the carbs offa the bike.. inverted, etc.

For the later carbs, you check the float level with the carbs on the bike, as you state. If the level is off, ya pull the carbs and adjust them. No need to place them back on the bike to test your "new" adjustment... Just pop them in a vise or prop them up level and check the adjustment again. (Throw a carpenter's level across the tops if'in ya can't position the carb bank level by eyeball)

Prom - I must respectfully disagree. You see, measuring the float height really has nothing to do with the height of the floats themselves. It's all about the level of the fuel inside the float bowls, while the engine is sucking fuel through them. No 2 floats are going to float exactly the same, and if .5mm makes a difference, then it's important to measure it accurately, under the proper conditions.

I do agree that the earlier carbs don't make taking this measurement easy, but the only real way to get the proper reading is to figure out a way to SEE the fuel level in the float bowls while the engine is running.

[prometheus578]

Women call me Mr. Average.

I see what you're drivin' at.
Technically correct, I suppose, but on the other foot... we're talkin' averages, yes?

What's gonna happen to that precious fuel level when the bike leans into a corner? How is one gonna measure and take into account how the level changes when the fuel sloshes from front to rear under acceleration or when shiftin' gears?
And what of the effect of the rider... Mr. JFMERK himself, on the measured fuel level? If'in he's a 300 pounder... that extra ballast is gonna put a bit of a backward tilt on things. (Both the bike and rider having rear ends that sag downwards)

...then it's important to measure it accurately, under the proper conditions.

Yes, but the conditions are not static... they're constantly changing. One can only strive to get a "general" setting that's generally good for the majority of conditions.

Now, don't get me wrong... I'm as anal as the next guy when it comes to tunin' things... but sometimes "Good Enough" really is good enough.

[TomRodgers]

Hmmmmmmm.....

I like this method.....


Bike runs....leave it alone. Bike doesnt run.... tinker till it does....

[jfmerk]

We'll know soon enough how the carbs are going to perform. LarryM, I have a hunch the float was shifted to one side. The gaskets fit nicely, no extra material inside the bowl and the tabs to adjust the amount of drop; I can only say I didn't change them and I would guess they've never been touched. My father-in-law was the only owner and he would never had messed with that.

Sometime I'll need to dive into the operation of the carb to really understand how the level in the bowl affects the operation. I have a OEM shop manual which describes it all, but right now... I just want to get going a hear it run for the first time in 5 years!

Thanks all!

[petejw]

hi jfmerk,
The float level affects acceleration,
to rich and it will bog, to lean and it will lag and be flat.

instead of using fuel to check for leaks, i find
it easier to wrap my mouth around the intake hose
and blow, with the carbs upside down, if there are any leaks you will hear and
and feel it, you can do this with the bowls on and
off.

[xsrider]

One cylinder lean during warm up

Cylinder on the right does not fire at first when warming up. I am wondering if it has to do with the choke[mixture] assembly.
Runs great when warm.

Anybody?

[DGXSER]

If by warm-up your saying when you use the choke/enrichment circuit it misses on that cylinder, then runs good after it is warmed up, then I have a good idea.

Inside the fuel bowl is a jet that serves only the enrichment circuit. I suggest you pull the bowl off that carb (if your lucky it is 1 or 4 and you might be able to pull it with carbs on the bike) and use a small stiff wire to ensure that jet is clean. Look in the bowl and you will see the small nipple spot where it draws fuel in, and then the hole in the edge of the bowl (the one that goes over that brass tube sticking up) that comes down to meet up with it. I took one of my wire brushes and pulled a wire out of it, sprayed a really good dose of carb cleaner down in both holes and ran the wire in each. Then used compressed air to blow the crap out.

If that jet is not clean and clear, that carb will not get much if any effect of the choke, and be very lean until warmed up.