[imslow]

If the needle jet "emulsion tube" (holding the main jet) does not seat directly on the small press fit insert in the bottom of the intake tract of a round slide type carb ( where the needle enters) , will the mixture be overly rich or lean? And what range of rpm would it affect if it is not seated by, say, a 1/32 of an inch? Will the engine run?

S

 

[jbranson]

Scott,
I would think that would make it run rich....it would have the same effect as raising the needle and would effect the same throttle opening range as would changes in needle position...around 1/4 to 3/4 throttle opening.
Basically you would be lowering the needle jet away from the needle as opposed to raising the needle away from the needle jet (as done by moving the clip).
1/32" of an inch would be equivilant to less than 1 notch on the needle clip I'd say. As the notches look about 3/64" apart.

What the hell are you up to Scott? Those old carbs are either right..or they are f'ed up. If one doesn't work right, or something bent, broke, cracked and can't be replaced you just throw it out. It's been my experience that with the old OEM keihins they are fairly bullet proof if everything is there and in good shape...however if anything on the BODY is messed up they are garbage. Often if the carb is reclaimed from one that was heavily deposited and corroded it will probably have problems. I've yet to find one that wasn't broke that wouldn't work. Check your idle air screw seat....they are often totally fucked...in which case you can throw the carb away. Pull out the idle air screw and get out your microscope and look at the seat, if it's bunged up in there you'll never get the low speed settings right as it will always be leaking way too much air/fuel.

And make sure you don't have the slides in wrong....cut away faces in the intake side. Check for worn slides, they will leak air around the sides.

Don't make those little babies more complex than they are, from 1/4 throttle on up they are almost impossible to screw up. From 1/4 down they can be very sensitive...but simple...a few components...if any of them is even marginal it won't like to run right below 1/4 throttle.
JohnnyB

 

[imslow]

ok i fess up. i busted off the bottom casting of carb that is threaded to accept the jet. When i put the new parts in i barely tightened it and it broke off . . . so i jbwelded it together. hasnt run right since.

yes, d'oh, the slides are right, and the needle seats are ok. this is more of a not run in almost any position. It's been fun, as ive learned all there is to know about how these things work.

interesting, though, i can get it running (one side) and the other (with the bad carb) gets going intermittently at high rpm. so the other day I put in the new needles that came with the rebuild kit , and bam, the thing won't run. at all. Also, of interest, it'll run great with the 120 jets (again, same symptoms as above) WITHOUT air filters, but with the 102 s i have to have the filters on.

blah blah balah. It'll work with a new used carb. I am, however, trying one last thing. As I really think it had something to do with the connection between the needle tube and where it meets the insert, i popped the insert down a little into the bore, and I am going to see how it goes with seating the needle tube up into the bore forcing the insert into a place that is comfortable. (in other woyds, when I insert the tube as far as it can go, it is not making contact with the insert. there is an "air tube" in the cast carb from the front of the carb that goes directly to the top of this just below the insert. If there isn't a seal there, all kinds of air will be sucked in. I think. ).> but its POURING RAIN ALL WEEKEND AGAIN so I won't find out for a while. Regardless, Tanks for the carbs.

s

 

[jbranson]

Scott,
If that stantion broke off when you put a jet in then it was corroded and F'ed up on the inside to begin with.

I've used the kit needles after I've compared them to make sure they are the same, sometime they are a bit rough from turning so I'll hit them with scotchbrite to smooth them a bit...not much cause their diameter is very important.

If it didn't run with the new needles they were either the wrong needles or they were hanging up somewhere and not settling into the emulsion tube properly.

When these carbs are right, which is really pretty easy to do, you can take them apart and throw them back together and they still start and run well. Like I said before...low throttle opening operation is spotty..they are after all intended for an engine almost twice as large.
JohnnyB

 

[imslow]

I thought that it was corroded after it broke off, as it broke off too easily. I learned my lesson a long time ago about overtightening things.

So this morning, I'm gonna put it on one mo time, and then heave the thing if it doesn't light up. The carbs came as a set, you know, all screwed together with the bracket, but one was in worse shape, probably from the bike being laid on it side on the ground for a couple of years. Been reading my fuel tech workbook this morning on the crapper, and the fuel around the needle jet and air supply to it are important for the low throttle settings.

But as you say, these carbs seem to work prettty well under a lot of variable conditions, as the side that I haven't touched has worked like a champ from the get go with all kinds of changes/issues with the bad side. The good carb just keeps going and going.

 

[imslow]

i'm 99 percent sure I licked the problem. took it out down the road and shes firing on both cylinders now and plugs look good.

on to hawk on tuesday. no place to test like the damn oily track.

 

[jbranson]

You still want the carbs I have or no?

Not that I'm trying to sell carbs...but if anything on yours is polish engineered in some way...it's going to cause you a headache down the road. Ask Aaron about how picky these bikes are about proper carb setup.
JohnnyB

 

[imslow]

i still want them regardless. If you have time, I just need the spigot cut off of the left side. Otherwise, I'll do it, no problem. It's easy to do.


It is still a dicey situation on the left side. I don't want a dicey situation. But it is a cool thing when they're both going.

 

[jbranson]

Scott,
I'll mill the spigot off both of them, ship them out Monday.
JohnnyB