Poor idle with solex carbs

727dvr · 02-06-2004, 11:53 AM

I have a 912 engine solex carbs in my 69 911 and I'm not sure about the year or model of the engine. It doesn't seem to be able to idle well. After it warms up it will idle around 500-600 rpm the red gen light flickering. If I try to adjust the linkage idle screw to get it up around 900rpm then when I stop at a light the rpms stay up around 2300. When you start to pull away from a stop, as you press down on the pedal the engine doesn't accelerate or bogs down, then suddenly it accelerates quickly to 1800rpm, then after that it accelerates smoothly and strongly.

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I'm new to this forum and would appreciate any advice I could get on this problem. Thanks

Ed in Sac · 02-06-2004, 05:38 PM

See the earlier post on "Webers-good/Solex-bad (maybe)". Sometimes these are distributer related problems not carburetion.

727dvr · 02-06-2004, 05:48 PM

How can one tell the specific model of the distributor on my car?

Thanks,
Danny

dferlauto · 02-06-2004, 06:14 PM

Last 3 digits of the serial numbers...

miles mulloy · 02-07-2004, 09:32 AM

Your carbs are probebly 35 years old and the throttle bodies are worn out. Fix one thing and something else in the carb wears out. Harry Pellow tried to tell me to forget the solex`s and get some webers.

I just couldn`t believe that I couldn`t fix the problem. And that Harry probly wanted to sell me a pair of webers. Well now Harry`s gone and I finaly fixed my carb problem with a used set of webers. Harry was always helpful with my questions. I just choked at the price of such small low tech carb.

They ( the webers ) still cost $450 plus a few odd linkage parts. New, the best I could come up with was almost $800.

New solex`s were advertized for $1400 last sping in one of the major Porsche suppliers, I don`t remember which one.

I should add that I repaced my disributor while misdiagnosing my engine problem.

mbm

727dvr · 02-07-2004, 10:19 PM

I was also wondering how I could tell which type and year of 912 engine is in my car.

miles mulloy · 02-08-2004, 05:38 AM

Harry Pellows ABC`s has the years for the numbers on the case. Post your numbers. They are on the the bottom of the case. I can`t find my copy. But I`m sure some one has a copy.

mbm

miles mulloy · 02-08-2004, 01:57 PM

webers for sale on ebay

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2457970826&category=34198

miles mulloy · 02-08-2004, 08:12 PM

Bidding has ended for this item (agharmann is the winner)

Go to larger picture Winning bid: US $497.25

atlporsche · 02-09-2004, 05:49 AM

is it bogging or choking?

it bogs when there's too much gas, chokes when there's not enough.

I've had the same problems as you, I fixed it by setting my float levels correctly, but what ABSOLUTELY fixed it was setting the acclerator pump correctly.

as for the idle problems, a good disassembly and cleaning should fix it...check your jet size as well.

sjd

eb61636 · 03-01-2004, 09:27 AM

The symptoms you describe are distributor-related not carburetion...90% of new owners have similar problems and come to the same conclusion.

Then they start adjusting otherwise well-adjusted carburetors and worsen the situation.

Leave the carbs alone util everything else has been eliminated as a possible culprit and is known good.

Buy an 050 distributor, or even borrow one, install it, time the engine to 33 BTDC at 3500 rPM+ and see how much different the car operates.

If you have the engine timed nicely, have new plugs, new plug wires, new coil, good generator, good voltage regulator, good compression in all cylinders, and no intake leaks and it still produces these symptoms, then remove the carbs and gently place them in the nearest trash can/dumpster or Ebay them.

Buy a Weber kit, jet it properly (32mmventuris a must) and forget about the days your engine wouldn't idle.

erik.

Big D · 03-02-2004, 05:51 PM

Mine is bogging. Set pumps to the rec. .65cc after two pumps. What is correct. Thanks DG

atlporsche · 03-03-2004, 04:08 AM

Big D, on the accel pumps, I just watched mine, and counted "one-one-thousand" while it peed...it would stop as I finished counting...and more is too much. I didn't have the little vial to do an accruate measurement...it's one of the few tools I don't have. I had to turn the adjuster nut in a LOT...the one that's on the arm with the spring...

more than anything, taking them off, taking the covers off and blowing them out did more to help than anything.

sjd

eb61636 · 03-03-2004, 04:57 AM

Big D,

The accelerator pump discharge amount is only half the equation, you need to take into account the nozzle size as well.

Say for instance you put in a 50 pump, and you are dumping .55cc for two full squirts, if you don't adjust anything and put in 40 pumps, you will dump the same amount, but in a finer, and longer (duration) stream.

You have to tune your pumps to where you need the help in your idle progression circuit. If you have a good transition from high idle to full-throttle, then 50s may do the trick.

If you have a rough off-dle to transition, you will probably do better with 40 pumps because they have a longer (duration) stream.

All of this is in reference to Webers by the way...I stopped fooling around with Solexes a couple years ago.

erik.

atlporsche · 03-03-2004, 05:16 AM

What I did got them close, the real test is choking vs. bogging...if it choked, then richen them...if it bogs, lean them...of course this is on the transition, what it does the rest of the time depends on the jetting.

having a one owner car, and having him be a friend of the family means he's a good data base when i call and say "you ever mess with the jets?"

sjd

Big D · 03-03-2004, 07:15 PM

Only other change was from 115's and 122.5 to 130 mains. I'm at 541 ft above sea level with big bore kit and bursch exhaust with K&n's. Benton says .1cc is plenty. Mine I measured at .65cc for two full strokes. Lot of difference. Guess i'll try one more time. DG