Dist. trouble ???/ idle erratic...

[C. Clark]

Greetings,
My problem is idle; I run 40 idf Webers with a .050 dist. The idle is erratic at times, primarily when the engine is warmed up after a long run. It's almost like the linkage is binding / sticking, but I've checked that all out, lubed all joints, everything is free, the idle runs as high as 2000 rpms them slowly returns to my normal 900 to 1000 rpm taking several seconds. I've checked and adjusted float levels, sync the carbs, did the timing, adjusted the valves. Recently I read about erratic idle with a defective dist. so I was wondering if any of you have had similar experiences and is there a definitive test other than a different dist.
Thanks,
Chas.
69/912

[ron69912t]

I have the same set up.

I added two throttle return springs to make sure the throttle plates were closing to their adjusted screw position. Cleared up the idle variation.

Thanks,

Ron

[C. Clark]

Ron,
Thanks but I did that too, I have considered stronger throttle return springs though.
Thanks,
Chas

[cgarr]

I think a too lean idle mixture can cause a long fast idle before dropping back to where is should be.

c

[craign]

Chas.

I had the same problem and it turned out to be a bad 009 dizzy. It only idled high when hot and would slooowly return to normal after about 2-3 minutes of just sitting and idling.

When the engine is nice and hot (and turned off), pop off the cap and gently turn the rotor with your fingers, when it is fully rotated, let go and see if it "springs" back all the way. Mine was stopping about 1/6" short of full return. New dizzy, no problems.

Dizzy's need a drop or 2 of oil on that felt pad under the rotor 1-2 times per year depending on if it is a daily driver or part time driver.

Craig

[C. Clark]

I tried all your ideas and then put my old .009 in, and guess what, all the stumbling and idle problems went away. I looked the .050 over and found no Bosch name stamped anywhere on the body, so I really don't know... but I always thought Bosch was proud and stamped / labled most everything. So I suppose I'll order a new Bosch .050 distributor and try again.
Thanks,
Chas.
69/912

[912UK]

I got a 050 the other day for my other halfs car and it was Bosch but a Brazil one. It looked ok and it works I guess but I too have the same idle high when hot and my dizy was bone dry so I have oiled it and greased the lobe. But I run org rebuilt (total rebuilt don't ask how much solex's) and 050. I get the same trouble as you guys

Double spring on the carb will kill the bushes but I too have the same trouble there must be something on the linkage to the pedal that needs a new bit or a mod to make it travel better.

Hmmm any ideas

Mark

UK

[jpamental]

Mark -

Check the path of the accelerator linkage: there are two sets of bushings (at the pedal and a bell-crank mounted on the transmission) and there's a spot where it goes up through the sheet metal to the engine fan shroud. Mine used to bind somewhat passing through the sheet metal. It's just bent in an arc to pass through, so you might be able to 'adjust' the curve a bit if that's the trouble. YOu can unhook the linkage from the carbs and work the linkage up and down to see if t moves freely.

Hope that helps!

Jason

[912UK]

cheers I have replaced all the pedal box bushes the bushes on the gearbox too I will look into the arch that you mention I have disconnected from the carbs and it is a bit stiff but the linkage is stiff too so both are not helping

Cheers

M

[Etrompke]

I have the same problem. Solex carbs. I just replaced the old 031 distributor that idled at 2,000 rpm when fully warm (hot). I put in a new Brazilian Bosch 050. It does the same, but at 1,800 rpm.
Next, I rebuilt the carbs, checked linkage. No better. BUT, I tried setting the timing with a new Sears timing light that has the knob on the back to compensate for the timing advance. I set it at about 25 degrees BTDC at 3,000 rpm when hot. That means it is now at 0 degrees at idle hot, and it idles at 1,000 to 1,100 rpm. BUT, it lacks torque and dogs down on cold acceleration, because the spark is not advanced enough. When I advance the spark, it revs up at hot idle.
I'm beginning to think that a distributor with a greater advance, like the 009, might work better, by setting it at TDC or a degree or two AFTER TDC at hot idle to get the rpms down, or about 35 degrees at 3,000 rpm hot and letting it advance fully on acceleration. Could still burn piston tops, but life has its risks. Anybody with a 009 distributor try setting it this way?

[craign]

I did some measurements with the same timing light comparing an 009 to 050.

All I did was drop the dizzy's in and with the 009 set the static timing to get the car started. Maximum curve I saw was 30 degrees at 3,000 RPM. On the 050 I had a pertronix ignition setup so it required nothing to start the car. Found a max advance of 33 degrees at 3500 with the 050.

Biggest difference I found between the 2 was better response at the high end with the 050.

Craig

[Etrompke]

Craig

Thnks for taking the time to do that. It sound like your properly functioning 009 and 050 distributors have similar advance curves in the car as well as in theory. That makes me think my 031 (old distributor) had worn out springs or some similar age problem, and my new 050 distributor may be defective. I bought it at Zims last week, and it came in a Bosch box, but it may not live up to the quality we expected ages ago.
I will do a check of the 050 distributor advance curve in the car (a friend who owns a couple 912s and a 356 recommended this) as well as a check of the advance curve of the old 031. I won't get to it until the weekend, unfortunately. It sounds like a common issue. I hope there is a common solution. Thanks for the help.

Ed Trompke

[Etrompke]

By the way, mine is a 1969 912. 147,800 miles. Engine rebuilt about 30,000 miles ago. Lived in Bay Area, California most of its life. In Oregon and in garage most of last 10 years.

[craign]

Etrompke,

You are not the first person I have heard about not being totally satisfied with a 050 dizzy bought through Zims recently. I wonder if they got a questionable batch from Bosch or something.

craig

[GTS Classics]

Chas:
I've spent years trying to figure out the same problem & never would have figured it out, but I picked up the Weber Porsche/VW tune up guide & learned that Weber now only makes right side carbs. This causes an uneven idle due to the way the shaft is turned around causing the idle surge. Go to http://CBperformance.com and look for the "WEBLINK" @$29.95. It basically makes the left carb a "true" left carb w/ the same type of throttle lever & spring as the right carb. Check it out, it works!

Good Luck,

Greg

[C. Clark]

Greg,
True, but nevertheless, when I put the .009 the sticky idle "feeling" went away. I ordered a new .050, a for sure Bosch this time and will post what happens with the new one. Thank you for the tip,
Chas.
69/912