carburetor blues wtf

[rdmcguy]

I have a set of carbs that no matter what I do break up (misfire)
at about 4500 rpm.
I have cleaned them, replaced mains pilots and diaphragms.
I am certain it is not electrical as I have put on a different set and they work fine.
Could it be choke or needle jet related?
Runs ok at low rpm.
Have had them on and off so many times I've lost count

[motoman]

Put on a different set of what?

[rdmcguy]

carb blues

I put on a set of CARBUETORS from a different bike,
known to be good.

[DGXSER]

Have you checked that the mixture screw tips are not broken off? I know that tends to be more of a low RPM issue, but still worth checking.

The two things most likely to contribute to upper-mid RPM issues is the needle height setting, and float setting.

Also, did you bench synch the carbs? vacuum synch them?

[rdmcguy]

carbs

Yes one of the mixture screws was broken off...
Repaired that ,bench sync'd them .
Also am having trouble finding a set of snap ring pliers long and narrow enough.to access needle jets

[motoman]

Yes one of the mixture screws was broken off...
Repaired that ,bench sync'd them .
Also am having trouble finding a set of snap ring pliers long and narrow enough.to access needle jets

Haven't seen where you've stated whether they are the early or later 34's..........snap ring pliers?......this is NOT sounding at all good. A bench sync is ONLY good to get things initially running.

[DGXSER]

So, that one hole with the broken screw, did you get it out, or drill it out?

As for the snap ring, I think MikesXS sells a set of long nose snap ring pliers. I finally buckled in and bought a set, makes the MC and those needles A LOT easier.

[Rasputin]

I am not sure of which bike in your sig that you are referring too.
The snap ring pliers make me think earlier carbs but not sure on that.
The carbs you used to replace them were the same type or from another year?
Just trying to glean a bit more info so we may be able to help better. Are there any mods we need to know about on your bike.
Just asking for more info like what type of jets you installed or what float heights you are running and all those other silly questions. Help us help you!

[rdmcguy]

carbs

The carbs are from an 80 standard,
Before I cleaned them they had 2h7-10 on the side
They are the early style with brass floats.
I set the floats at 23mm.The bike the carbs are on has a kerker header,
and emgo pods.As I live at 5280 feet elev.i jetted for altitude.
127.5 mains...42.5 pilots
I verified these sizes at my local shop and they match what I have in a different set of carbs that work fine.
I have switched and swapped the carbs with my other bikes to verify that it wasn't elec or otherwise.
same problem no matter which machine
Btw. thanks to all in advance

[motoman]

I am not sure of which bike in your sig that you are referring too.
The snap ring pliers make me think earlier carbs but not sure on that.
The carbs you used to replace them were the same type or from another year?
Just trying to glean a bit more info so we may be able to help better. Are there any mods we need to know about on your bike.
Just asking for more info like what type of jets you installed or what float heights you are running and all those other silly questions. Help us help you!

See we have the same thoughts/questions........

[motoman]

He sent me a PM. I know the bike now as he is the one who generously offered up his tools, place to make repairs when John(J.W.Hughs) had the head-pipe stud breakage issue on his and his sons LONG trip. I had went over there(Denver) and met him and I rode with John's group on south thru the rest of Colo. Two solid days of rain, but still enjoyed the ride and the re-visit.

[motoman]

Sorry Joe for not assocciating the screen name to you. Yes, I sure did notice that upper mid-range thing goin' on out that 4into1 when you was leading us all out of that rush hour zoo in Denver. I would like to suggest you pull that timing cover off, and with bike idleing, every half inch, use two hands and pull on the pickup coil wires firmly. If that insulation stretches anywhere, the wire internally IS broke and may have had only one strand holding it or wleded itself back together from the resistance. If all checks out there, then remove the vacumm advance from its mount so you can unhook the rod from the advance assembly. That advance assembly HAS to be floppy loose as there is a minimal vacuum pull(ported vacuum not manifold vacuum) on that can to advance that assembly. If it rotates even a bit stiff, there inlies SOME of the problem. Believe 3Phase just recently had a thread and pics on how to correctly remove all that and clean up the mechanical and vacuum advance assembly. Someone here can post you that thread quicker and easier(not a puter guru)than I. Can do it, but molasses would produce results faster. Rule of thumb Joe is when adnormal issue come out of nowhere, ignition before fueling...always, unless you know the carbs are still not close to correct. Then you WILL be scratching your head, flipping a coin and chasing your tail. Check all that CLOSELY and let us know here the findings. BTW, I'm not beyond another road trip 'over the hill' if necessary. Thanks for the reminder e-mail, Brant.

[CRXSi90]

So this isn't a case of the Emgo pods rearing their head with the inner lip blocking air flow?

[bikerphil]

Early style carbs with brass floats use the 25.5 mm (1") float setting. Probably running a bit rich with them at 23mm.

[motoman]

Early style carbs with brass floats use the 25.5 mm (1") float setting. Probably running a bit rich with them at 23mm.

Just saw that..............hmmmm.....80 basterdized carbs to boot having the brass floats. Not particularly an issue, but yes, 25.5 float setting for the brass floats. And yes, was rich smelling with the occassinal following come to think of it.