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jlaird

jlaird

Great Pumpkin
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Now I feel like a stupe.

Starts fine, runs well but can not get the carbs balanced.

Front carb runs with piston up a bit and can not get it down.

Have set rear carb to best running, when I go to front one it will not settle down.

Can not find any air leakes with carb cleaner and the vacume advanced is blocked.

Of course the carbs are seperated with the throttle shafts loose.

I can get it down to about 900 RPM but it does not want to accelerate smooth because of the unbalance I suspect.

Any ideas on what dumb thing I have not done?
 
Have you used the old "hose-in-the-ear, listen to the hiss" test? It sounds like the front is sucking more air!
 
I have never fooled with the dual carbs on a spridget, I bought mine and it had the weber on it. I hav fooled with a lot of motorcycles with multi carbs. Its best on them to use one of the multi vacuum gauges with the murcery readout for each carb. I don't know if this would work for that setup or not. Is there a tap or anything where you can check the vacuum on each side of the intake? You could probably rig up something with two small jars with equal amounts of water with a hose run into each one and connected to an intake half. the water levels should drop to the same amount in each jar when the motor is started. That is the only way I know to syncronize both carbs.
 
Yep I use the rubber hose trick seem to be the same right now but I can hear when standing back that they are not right as the engine has a lope in it.

Advanced the timeing another 5 degrees and it helped. That is at 1000 RPM, also note that when comming down the street and shove the clutch in the engine tends to die. I suspect due to the increased load with the clutch in vs no clutch when adjusting.

Will keep working on this till I get it, keep talking to me. I need brain jogs.
 
jlaird said:
also note that when comming down the street and shove the clutch in the engine tends to die. I suspect due to the increased load with the clutch in vs no clutch when adjusting.

Will keep working on this till I get it, keep talking to me. I need brain jogs.
Click to expand...

Hmmm, that certainly doesn't sound right!
 
Remember it is one of those carbon throw out bearings, lots of drag there.
 
/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif My thoughts exactly!! /bcforum/images/%%GRAEMLIN_URL%%/confused.gif
 
This isn't a discussion of drag on a carbon T-O bearing. This is a question of synchronizing carbs. The weber has the advantage of having both throttle plates connected and they rarely go out of adjustment. Duel webers do that! Duel SUs also do that.

You don't have smog carbs do you?

The throttle plates firstly must be adjusted for completely simultaneous operation. This can be done nearly as well visually as with the rubber hose. With the idle adjustment screws loostened, you must feel that they both close completely and open together. Different piston heights can not be tolerated.

Both carbs must also have free moving pistons and equal float levels.

Timing should at least be nearly right. This can be done statically also. Then the rubber hose can be used. It should only confirm correct visual and tactile adjustment of the throttle plates. Then comes the mixture adjustment tested when running. Both low speeds and high speeds. I have no idea of what type of mixture adjustments you have in GB.
 
racingenglishcars said:
I have no idea of what type of mixture adjustments you have in GB.
Click to expand...

??? /bcforum/images/%%GRAEMLIN_URL%%/confused.gif ??? These are regular old SUs withe the mixture adjustments made underneath the carb! I agree with the rest of your advice, and am just commenting that the T.O. bearing should have no effect on the running of the engine with well tuned carbs!!
PS we are about 3000 miles WEST of GB! /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
This is an H1 carb on a Bugeye.

I can not shut the engine down with the idle screws all the way out. About 1100 RPM or so at that point.

Seams preaty good at present advanced timeing a bit and carbs preaty well balanced about 1500 RPM idle.

I also note that when I accelerate the engine it stumbles a bit then catches strong. Like it is not getting enough fuel.

Have tried setting by the book, no joy. Have also checked for air leaks with carb cleaner, no reaction at all which is great, no air leakes anymore.

Hehe, 3K and hard on in a corner is awsum.
 
My weber dgv only uses one carb barrel for the whole engine until you push the pedal far enough then the second opens up. There is nothing to worry about syncronizing on it. Good luck getting those carbs setup Jack.
 
What are you doing that for Jack? And with no seats either!!! What are you sitting on/in?
 
Hah, have a wooden seat bottom I knocked up with a few peices of wood and a mattress pading folded up on it. Works preaty well in fact, lean against the corner and way back. Shoot lots and lots of room for big guys.
 
If you're getting 1100 rpm with idle screws all the way out, you have either one or both throttle plates partially open. Just a little bit. This can also be from the plates being a little off center int the bore, that is not correctly alligned or maybe even loose on the throttle shaft.
 
Gotta be ~something~ holding the throttle plates open just shy of fully shut. Perhaps with the tops off and pistons out you could do a visual recon of the blades with the idle screws backed off, linkage loose? Dental mirror and flashlight. They should be able to be closed completely. Bear trap closed.
 
Hmmm, Joe Curto installed them but maybe I got one pushed a bit, will check right away. Sounds right and like a plan.
 
We'll wait right here! /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
Great call Doc, was the front one of course. The return spring was a bit too tight on the shaft which kept the butterfly from fully closing.

Now for a real balance and tuneing job.

Later.
 
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