Carbs & Other Monkey Motion!

[Sweetheart912]

CARBS & OTHER MONKEY MOTION

Thanks so much to the few folks who sent notes off line about the stuff I posted on the Weber 40IDF conversion. Glad it helped. One critic thinks I shouldn’t waste his time with long posts that are confusing to him….sorry, just trying to help by passing some on some stuff I learned. Never claimed to be a Maestro (RIP) or a Hemmingway.
While I was thinking about it, a few notes regarding the “Whole Carb System”. Remember that the Weber or Solex reaches all the way to your gas pedal. You can get everything synched up and happy in the back of the car at the carbs, then the first time you hit the gas pedal to go for a test flight, things get all revved up, and idle hangs high or some of the other malady appears that have been described in so many posts. AND then you immediately want to tear into the carbs & rejet, rebalance etc, but before you do…..
Think about the mechanical engineering of the whole system. The carb arms & balls on the carbs, 1 rod on each carb that runs from a parallel thick rod behind the shroud; 1 rod behind the shroud on a small bell crank at the bottom of the shroud; 1 rod-wire that runs to one side of the bell crank at the trans; 1 rod from the bell crank to a barrel coupler, a rod thru the tunnel to another bell crank up front; 1 rod to the accelerator pedal-at least 9 swivel points! That’s a lot of monkey motion folks just to get good idle and loud pedal! Every one of these guys rotates on a pivot ball that probably has petrified factory grease on them ergo slow or binding movement. The pedal is actually one additional link to consider, as it has 2 bolts holding it to the floor – are they loose, or the pedal rusted at the floor? Anyone of the above out of whack will hose up your smooth carburetion & acceleration.
First, make sure the thick rod that both carb rods hang on is laterally tight, level, and the arms drop freely. The 1-2 side can be adjusted on the long spring steel tang by loosening the 3, 10mm bolts by cyl #1. If the short 3-4 side welded on tang is bent out of whack, place a crescent wrench, to size, on the tang and bend to position to make the rod drop freely.
Check the back side of the shroud ball rod and bell type crank for grease & adjustment. Should have washer & cotter pin to hold it in place.
Check the metal rod/wire that runs thru the oblong hole in the sheet metal – does it rub? Adjust and tweak as required. Bending this guy a whole lot to clear is not the answer – it’s a better chance the bell crank bushings are shot.
Check the bell crank bushings on the trans. Unless you know they have been replaced, the 35+ year old plastic is probably gone & WILL cause binding. Grease bell crank shaft and reinstall. Washer & cotter pin hold it in place.
Check the barrel shaped coupler running between the short bell crank rod and the long one that runs thru the tunnel. Chances are it’s rusted, the rubber is weak and therefore puts extra play into your system. What the heck, as long as you’re under the car it’s a good time to adjust the clutch, if needed.
Check at the front pedal. Is the pedal stop in right? Is there slop in the rod & small crank there? If so, it may have to come out to fix properly. At that point you might as well rebuild you pedal cluster with the whole new bronze bushing set. Good time to check & clean the stop light switch too-its right there on my 69.
In the Weber conversion series of posts I mentioned having someone depress the pedal to see if you had full throttle at the butterflies. Sorry for not mentioning all this, but I made some assumptions that those things are OK. I had checked or repaired all the above the prior weekend, before I started the carb work – ended up replacing the bell crank bushings and decided to rebuild the pedal cluster since it was a little sloppy. I made sure every pivot point is greased with a good lithium grease. With all the bushings and adjustments and greasing done and lined, up my pedal moves @ 1.5” or so from rest to full throttle at the carbs.
There are no special tools needed to do this. It took about 3.5 hours to do it all & that included paint drying time on the cluster. Don’t let me kid you, it was little pain & sweat, but not hard. Parts cost @ $30. Add @$ 15 if you need the barrel coupler. If I have any part wrong here, please let me know so we can get good info out. I always say refer to the manual, but a whole story is not in any one manual I could find, besides a factory shop manual.
IF all the monkeys are lined up, and all else is synched in the carbs, and your timing, point gap, plug gap is right, your accelerator pedal is no longer a pedal-it is a TRIGGER! Happy 912 Motoring.
Cheers, George

[craign]

George,

I appreciate you posting your experience with Webers, I am a carb dummy and posts like yours are HUGE help to dummy's like me.

I highly recomend a "Weber Tech Manual" by Bob Tomlinson at www.cbperformance.com, best $10 I ever spent for my 912.

Craign

[Jones Low]

George, good post. Thanks for sharing the info. Newbies, oldbies, we all want to be wanabies. Keep them coming.

[bemumford]

George,

Excellent posts. Pay no attention to the critics. Wish I had access to this information before I learned many of these same lessons the hard way. All is well with my 67 now, but it took a lot of experiment to get it that way.

Ed