#2 and #4 not firing after rejet

[yogib]

Those are 34's you got from me,I did measure the venturi on them.Unfortunately they didn't put part#'s on the bodies off the 1100"s so I don't know the year they came from.My guess would be the bodies should be the same for 34mm 16 valve engines.I don't know for sure though.If there are differences the working parts would be different.It's got to be somthn' simple,gotta run for now stop back later.Don

[hungryman]

Not a stupid question at all. When I'm behind the wrench, nothing is stupid :-D

The screens should be fine since I just cleaned them prior to changing the jets, but I did not check the bowls to see if they had fuel in them, though I was just thinking about going out there to do that. I'll remove the drain screw to ensure that fuel is at least getting to that point.

I did notice when I removed the carbs just now that the butterflies for one and three had a sheen of gas on them, but 2 and 4 were dry. Kind of makes sense though... if it's not firing it won't suck in fuel to the cylinder, correct?

No, an air/fluel mixture should be delivered wether or not it's firing.

[yogib]

Are you SURE you have spark at both 2&4? The coil could be bad or the lead came off the coil.I'd double check JC.Don

[KEITH KRAUSE]

No, an air/fluel mixture should be delivered wether or not it's firing.

That's what I told him earlier Steve. I also told him the "sheen" he sees on the two wet throttle plates would be fuel coming out of the pilot circuit bypass ports. I described how the fuel gets to the bypass ports.
I'm thinking the two carbs that apparently aren't supplying fuel probably have dirty/clogged bypass ports. If the tiny ports ARE clean, then I'm thinking vacuum issue.

[J_C]

Thanks folks, I'll double check the coil and the bypass ports, though I definetely did see a blue spark when the ignition was on. Lots to do this weekend!

Not sure how the bypass ports would be clogged as I soaked them in carb cleaner for severals hours each, but I'll see if I can indetify them and blow some air through there

[hp1000s]

This might be dumb, but, could the replacement bodies be the ones that have open vacuum ports for the fuel petcock?

[J_C]

Carb #2 (Replacement) has the vacuum port to the petcock... why, what are you thinking?

[hp1000s]

Like I said, dumb, but if you've got open(to atmosphere) vacuum ports, it could lean mixture as well as disturb the vacuum signal for fuel delivery through idle circuit. It was just a thought, 'cause I'm no expert on CV carbs.

[KEITH KRAUSE]

Like I said, dumb, but if you've got open(to atmosphere) vacuum ports, it could lean mixture as well as disturb the vacuum signal for fuel delivery through idle circuit. It was just a thought, 'cause I'm no expert on CV carbs.

I think you're talking about float bowl venting. No vacuum present, just venting. The common practice when running pods is to remove any float bowl vent lines and leave the vent ports open. If you don't remove them, a vortex effect forms in the lines and can cause the fuel level in the bowls to lower/fluctuate and the result is fuel starvation. This condition worsens in crosswinds and while freeway riding. Some carbs suffer from this effect more than others. The VM carbs are very sensitive to it, the CV's seem to be less effected but still effected.

[KEITH KRAUSE]

Thanks folks, I'll double check the coil and the bypass ports,

Not sure how the bypass ports would be clogged as I soaked them in carb cleaner for severals hours each, but I'll see if I can indetify them and blow some air through there

The bypass holes are very small and sometimes don't clean out well without special attention given.
They are right where the upper throttle plate nearly touches the carb throat.
The reason I mention these is because it would be easy to check for one thing.
My reasoning is because you say you tried to idle the bike, then noticed the two cold cylinders. Obviously, you're on the pilot circuit COMPLETELY at idle. If no gas is wetting the plates/cylinder/plugs, then the pilot circuit must be plugged somewhere or there's a vacuum loss. You said the carbs were taken apart and all jets replaced, all carbs recieved the same jets/parts, I assume very clean. That SHOULD rule out any dirty parts/jets and that just leaves the possibility of the replacement carb bodies having dirty ports.
If the entire pilot circuit is clean, then the only reason fuel wouldn't reach through the clean pilot jet/passages to the carb throat, is a vacuum issue not drawing fuel.
I believe you also said float levels were set to factory levels.
I've never liked swapping carbs from different years/models. There can be small differences that many of us just aren't aware of, but can cause problems. Not lecturing you, I know you're just wanted to replace the bodies because of the stripped mixture screws. But I've read many times before that unknown problems come up with carb swapping.
Hopefully, we'll figure the problem out.

[J_C]

Hey guys... took the plugs out after cranking for about 10 seconds.... they didn't really smell like gas.. more like oil? But then I took one out for comparison, and it didn't smell like gas either.

Decided I'd try to start the bike up.... 1, 2 and 3 heated right up!! I'm not sure if that's because the idle is set high right now (it was running about 3000 rpms) so it may have been skipping the idle circuit?

The interesting news is that #2 was from yogib... and the #4 was from the 82 gs1100... so maybe it is just passages instead of bodies. I'll take the plugs back out once it cools a bit, try dropping the idle and see what happens as well. Then I'll pull the carbs to see if I can do anything else about those passages

[J_C]

#2 fired again on low idle so I think that one's in the clear! We noted that the 1,2 and 3 carbs had fuel on the butterflies and there was fuel on the inside of the hoses going to the block. #4 was dry on both areas as well as the plug. Obviously fuel wasn't getting through.

I finished using a wire to clear out the pilot circuit holes in the venturi. I also blew a bunch of air through there via the pilot jet hole, and replaced the pilot jet with a cleaner one. Tomorrow I'll start it up!

[KEITH KRAUSE]

Sounds like you're making progess. Gotta have fuel in the cylinders to get combustion. I'm assuming you have good spark at this time to all four.
Now just find out why the 4 carb isn't delivering fuel and you should be ready to synch and test.
If you've got spark, fuel and a good bench synch and the idle adjusted enough to start, it should start up and you can vacuum synch.
Be very careful with cleaning wire. The carb material is fairly soft. Squirt lots of cleaner and lots of air to get those ports/passages clean. I use 150+ psi sometimes.

[J_C]

Hrmm... Well it started right up this morning, but still no #4. I swapped the #1 and 4 plugs just to double check, 1 still worked, 4 did not. Did a compression test on a warm block. 150psi, so that also seems pretty acceptable. Back to the carbs again

I'm going to go down and buy some carb spray, though I don't have compressed air. Looks like I'm rebuilding the carb again.

I'm also dipping the old broken #4 in the hopes that it might be able to be jbwelded and used for comparison.


EDIT: oh I also checked the boot and butterfly and it seems that fuel is getting to the cylinder now... just must not be enough?

[J_C]

Hrmmm Developments!

I completely broke down #4 and went to town with the carb spray. I hit almost every passage there is multiple times and manually blew them out. I had a really good feeling when I reinstalled the carbs and......

No It didn't heat up. In somewhat mild frusteration I cranked the throttle to see what the other carbs were made of and... low and behold... a continuous backfire in the right pipe! My father (partner in crime) reports that the #4 header has suddenly become very hot. #4 is (back)firing! I drop the revs from 6000 back down to 2000 and the backfire lessens but is still hanging in there. I drop back down to idle and it goes away. It may have completely stopped firing all together, but I won't know until I let it cool and go fire it up again.


Backfiring.... this is certainly new.... \\/