Carb throttle linkage adjustment.

whackit · 02-01-2010, 08:44 PM

Hi all.

I just reinstalled my throttle linkage after a complete rebuild. The carbs were switched from zeniths to PMOs so I have all the correct parts but the stroke seems really short at the pedal (full travel of the pedal is about an inch an a half). I can't figure out if there is something to adjust. I have the correct bell crank at the transmission. I am re using all my parts from the zenith linkage so it should be all correct according to Richard Parr (PMO) Both carbs have the same amount of stroke at the carb so it's not that. Does anyone have an idea how to remedy this.

have searched and there are some threads which mention adjusting travel by adjusting some rods but nothing specific.

Cheers.

french911 · french911's Garage

Is the crank fitted at the rear of the engine 180 degrees out. Had the same problem and that is what cured it. Difficult to find pictures of the orientation.

Barry

french911 · french911's Garage

Just read my reply and even I can't understand it so I have been outside and checked mine and made a drawing of the linkage and rod positions. So rather than waste a thousand words here's the picture, hope it helps.

James Brown · James Brown's Garage

everything sounds correct to me, does the throttle open carbe all the way? your linkage looks correct.

french911 · french911's Garage

yes, with my foot to the floor the butterflies are wide open, in fact I have adjusted the stop bolt on the pedal to limit pedal travel so I don't stress the linkage.

Barry

whackit · 02-02-2010, 07:13 AM

my linkage is installed that way although I do believe the problem lies there. I have been messing with the rods on either side and it seems to effect distance.

James Brown · James Brown's Garage

Each time you adjust a rod length, you must adjust all the other rods. Meaning, shortening one=lenghing the other. Also, the rod that goes through the rear of the engine down to the throttle cable has an "elongation" that allows the carbs (or injection) to be operaited (opened) with out the throttle cable being moved. So make sure all the "slack" is out of the cable to rod linkage prior to adjusting the carbs/bellcrank assembly. Use a assistant to verify full opening of the throttle.

whackit · 02-03-2010, 05:29 PM

I don't have a cable. mine is all rods (later version).

snbush67 · snbush67's Garage

The problem may be at the other end where the long wire rod is on the pivot at the transmission, check to see that it is aligned correctly and is not binding at that point.

James Brown · James Brown's Garage

there all rods Wackit, If you look down on the transmission you can understand how the RODS work. If they were all solid from the gas pedel to the carbs, it would be very hard to BLIP the throttle at the engine without the device Snbush67 is talking about. You can have slack in this device that would do just what your discribing. I beleave your engine bellcrank linkage is correct, time to move down the RODS to under the transmission and into the tunnel.

jwetering · jwetering's Garage

Hmm....

Have you tried adjusting the rods so that when the pedal is up the butterflies are closed and when the pedal is all the way down the butterflies are fully open? That would be what I would do.

Just kidding - I have faith you'll figure this out.