2 left side carbs not drawing vacuum..

[Bill Seward]

I did a carb teardown and cleaning last week. New main and pilot jets, new mixture screws and rubber o-rings, new diaphragms/ slides, new lower carb boots. Hooked up the Morgan Carbtune and the left cylinders show no vacuum. The rods don't move. I sprayed some carb cleaner around the boots, no difference. Shooting some into the offending carbs causes an immediate reaction, those cylinders start firing for a few seconds. Left exhaust pipes are not heating up. Thinking I will be pulling them off again to see if there's a leak somewhere.

Any advice from those who have had this problem? The Bike ran on all 4 before doing the carbs. They have never been removed or disassembled prior to this. Not having an ultrasound cleaner, I used a lot of carb cleaner and 100 psi air gun on orifices..

 

[Fire-medic]

Sure sounds like a very fundamental blockage/obstruction there, Bill. You might want to try clearing-out the ports where the balance hoses connect. Is there any restrictor on the individual lines? Maybe you have blocked restrictors, or if they're adjustable they're all the way closed.

Remember that in the front ignition coils, the right coil fires the left plug and the left coil fires the right plug.

On used VMaxes, I've found that someone was careless in messing with the CV diaphragms, the circumferential rubber ring was out of place, and pinched, it's easy to-do, if you're ham-fisted and careless.

The fact that it's happening to the two left carburetors, I'd be looking at the linkages actuating the two left carburetors, and their fuel flow. Did you check the fuel hoses to them for splits?

 

[Bill Seward]

Not yet, but no fuel is leaking. Ive got to take another look at the linkages when I pull the carbs.

 

[dannymax]

Could be your banks are way out of sync with each other. Were you able to get a satisfactory bench sync?

 

[Bill Seward]

I'm gonna pull them off, look at the boots to see if there is any sign they were leaking, and carefully look at linkages. May as well re-check float levels and do a bench sync too. There is a small vacuum generated when I manage to get the engine revved up to around 4K, but nowhere near the right cylinders. Leading me to think I messed up sealing the boots to the intake manifolds. I'll keep posting on this, and share what I figure out about the problem.

 

[02GF74]

Stupid question but does this gauge have restrictors, dial type gauge have them to stop the needles from bouncing - I can't see from photos that these do.

Also you swapped the hoses around to rule out any issues with the gauges?

Check the throttle adjustment screws, the ones used to sync up the carbs.

 

[dannymax]

Try turning in the right front sync screw while it's running...see if it picks up the left side carbs. Try the 4K rev to see if the minimal left side vacuum has changed.

 

[Bill Seward]

Thanks Dan, I'm getting back to it later today.

 

[Bill Seward]

Dopey me... Seems like the slides in the Carbtune have become sticky, Switching the hoses shows vacuum on the left cylinders. gotta have a look at the Carbtune.. Still won't take the gas, though.