Weber carb problems

[chope97]

My 73 runs well except at idle. It seems to run rich. I took the top of one carb off and saw what looks to be a black I have worked on Weber's before in the past Oh by the way I have not started my car in 6 weeks, the bowl was completely dry with some dried particles in the bottom. What do you think is causing the problems with my carbs? What should I do? I have a rebuilt kit waiting for me but I want to make sure I get the problem fixed, spring is just around the corner time to drive and have fun. Also the bottom of the float bowls seems a little greasy like old gas. Thanks in advance

 

[Baikallackierung]

Power valves bad? Read below to get started on your issue:

Explain the "Jim Rowe Power Valve" modification, please

I've seen this mentioned, but no link or explanation for it anywhere, EVEN using the search function here. Anyone care to elaborate on exactly what the "Jim Rowe Power Valve modification" IS???? I've finally hooked a wideband / AFR gauge into my 3.0 with 38/38 Webers and have decent fuel...

e9coupe.com

 

[Stevehose]

float and/or float valve stuck or have debris in it?

 

[Ohmess]

That black looks to be from backfiring through the throat.

Do you have an autochoke assembly? If I remember right, these are designed to retract only when warm, so if the coolant passages are gunked up they will not retract and you will run rich at idle (and other times as well).

Given the black soot, the gas residue you describe, the particle deposits in the bottoms of your bowls and the possibility that those deposits are fouling your float valve, I would rebuild and see if that does the trick.

 

[bavbob]

The debris is not de-novo from the carb, you should peek in the tank and also blow out the lines. If all that is clean, why not try a round of Seafoam?

 

[tochi]

My 73 runs well except at idle. It seems to run rich. I took the top of one carb off and saw what looks to be a black I have worked on Weber's before in the past Oh by the way I have not started my car in 6 weeks, the bowl was completely dry with some dried particles in the bottom. What do you think is causing the problems with my carbs? What should I do? I have a rebuilt kit waiting for me but I want to make sure I get the problem fixed, spring is just around the corner time to drive and have fun. Also the bottom of the float bowls seems a little greasy like old gas. Thanks in advance

In addition to Ohmess's suggestion (sticky or poorly adjusted choke), the “black” film depicted on what appears to be the primary barrel may also be due to crankcase blowby. How or where is your valve cover breather ducted? (If blowby is ducted to one carb - and not the other, is the non-ducted carb cleaner than the pictured carburetor?)

Fuel has a tendency to evaporate when exposed/vented to the atmosphere. Evaporation after six weeks of exposure is not surprising, especially if sitting in a warm climate. Metal particulates are likewise not necessarily unusual as constantly moving/vibrating carburetor and mechanical pump parts can wear. Running an inline pre carb fuel filter?

 

[chope97]

My breather hose comes off the valve cover and goes down toward the ground, it is not attached to anything for now.

In addition to Ohmess's suggestion (sticky or poorly adjusted choke), the “black” film depicted on what appears to be the primary barrel may also be due to crankcase blowby. How or where is your valve cover breather ducted? (If blowby is ducted to one carb - and not the other, is the non-ducted carb cleaner than the pictured carburetor?)

Fuel has a tendency to evaporate when exposed/vented to the atmosphere. Evaporation after six weeks of exposure is not surprising, especially if sitting in a warm climate. Metal particulates are likewise not necessarily unusual as constantly moving/vibrating carburetor and mechanical pump parts can wear. Running an inline pre carb fuel filter?

 

[chope97]

In addition to Ohmess's suggestion (sticky or poorly adjusted choke), the “black” film depicted on what appears to be the primary barrel may also be due to crankcase blowby. How or where is your valve cover breather ducted? (If blowby is ducted to one carb - and not the other, is the non-ducted carb cleaner than the pictured carburetor?)

Fuel has a tendency to evaporate when exposed/vented to the atmosphere. Evaporation after six weeks of exposure is not surprising, especially if sitting in a warm climate. Metal particulates are likewise not necessarily unusual as constantly moving/vibrating carburetor and mechanical pump parts can wear. Running an inline pre carb fuel filter?

I have a new fuel pump and a new in line fuel filter. I am using the stock air filter housing. I live in Maryland and the car sits outside under a car cover. Last year we replaced the cylinder head because the old one had a worn lobe.

 

[bluecoupe30!]

This may not be connected to your symptoms, but there have been many useful suggestions for you to follow up and try to solve your problem. In my case, I could not get the mixture for my pair of Weber 32/36 correct. Ran rich. Tried everything you could think of. Then finally removed back carb and found the mixture screw wasn't doing anything at all, when turned. As you may very well know, you make adjustments when warm, and there is really no straight access to the mixture screw, so, when you attempt to make the quarter turn adjustment to match the quarter turn adjustment on the front carb, it is not as precise as you would like as the flesh on your hand has begun to burn as you come in contact with the now very hot engine or manifold or coolant hoses. This masked the fact that the back carb mixture screw was gummed up with the varnish/crud of old gas.
Removed carb, chased the mixture screw thread, flushed with carb cleaner, and found the carb could actually be adjjusted again! Big difference. Dialed in and synchronized for the first time in a long time. Old fuel gums up every carburettor, eventually.
Good luck with your carbs and let us know what really solves your problem.

 

[chope97]

Thank you everyone for your comments. I purchased this car in 2017 in an auction in Pa. It came from Cali. It still had the blue plates. I have found lots of dubious fixes and repairs for example it has two antennas manual in the front and electric in the rear. It has two flasher buttons, don't know why. It is a nice looking car with a non E3 blue paint color. When I took the top cover off of the carb, I noticed that the screws were not tight. I have enjoyed working on this car little by little and still drive it each week. It is part of the fun of owning an old BMW. It also has a new ZF trans with the dip stick on the driver's side. The gear shift is offset to the left, so my console does not fit right. I have lowered it and pit Bilstein HD on it. This is my third Bavaria since the 80's. I also own a 71 with a 3.3 and 5 speed does not look as good but runs better.

 

[tochi]

Thank you everyone for your comments. I purchased this car in 2017 in an auction in Pa. It came from Cali. It still had the blue plates. I have found lots of dubious fixes and repairs for example it has two antennas manual in the front and electric in the rear. It has two flasher buttons, don't know why. It is a nice looking car with a non E3 blue paint color. When I took the top cover off of the carb, I noticed that the screws were not tight. I have enjoyed working on this car little by little and still drive it each week. It is part of the fun of owning an old BMW. It also has a new ZF trans with the dip stick on the driver's side. The gear shift is offset to the left, so my console does not fit right. I have lowered it and pit Bilstein HD on it. This is my third Bavaria since the 80's. I also own a 71 with a 3.3 and 5 speed does not look as good but runs better.

My suggestion regarding blowby was merely that, a suggestion. As others also suggested, a sticky or lazy choke, and questionable carburetor jetting and/or ignition timing might negatively affect low speed/part throttle engine operation. It might be interesting to know whether you inspected the pictured carburetor throat prior to taking possession. Maybe . . . there was a preexisting problem that was easily sorted, but the carburetor innard was left in a blackened condition. Given your followup post, perhaps some of these things are . . . not to be unexpected.

In any event, best of luck.

 

[Ohmess]

chope97 - have you done a simple tune up on the ignition system? This is always recommended before attacking carb problems.

 

[chope97]

Timing is a problem the car has a newer transmission so there are no balls or marks on the flywheel I have to time by ear. I do have a carb sync tool for Weber's, idle has always been a little rough. the valves have been adjusted, I have electronic ignition, new wires, cap rotor, like I said replaced the head with one with a good cam, it is carbs or vacuum leak, right? might be snow in the DC area tomorrow

 

[Stevehose]

Do you have a timing mark notch on your harmonic balancer? If not why not paint one on and time from there?

 

[Dick Steinkamp]

Do you have a timing mark notch on your harmonic balancer? If not why not paint one on and time from there?

Great idea! Fabricate a stationary pointer and file/paint a mark on the balancer with #1 at TDC. Then use a dial back timing light to know exactly how much advance you have at every RPM.

 

[HB Chris]

Set the crank to TDC based on marks on cam and both valves on #1 pointing downwards, now paint a TDC mark on flywheel, isn’t 22 degrees before TDC 6 teeth? Don knows this by heart. Make another mark there or just use an adjustable timing gun.

 

[Billw]

I recently purchased a 72 Bavaria. It had lots of new parts including two new Weber 32/26 carbs on it and fresh paint but was not sorted out. It also would not hold an idle. After chasing a few red herrings, I checked the idle jets and they were .06's went down to .04 and was able to attain a smooth idle and actually think I could go smaller but .04 is as small as they go. Hope this helps. Good luck.

Billw

 

[chope97]

Has anybody seen the $100+- 32/36 weber type carbs and $100 38/38 carbs on amazon? Most have electric chokes which would make the engine bay look less messy. Anybody brought one?

 

[wkohler]

Has anybody seen the $100+- 32/36 weber type carbs and $100 38/38 carbs on amazon? Most have electric chokes which would make the engine bay look less messy. Anybody brought one?

I can't decide if I want the SherryBerg, the NENKUTEN, THUNDERMINGO or the VergasRetor It's all a matter of which decal would look better on the window I guess.

 

[Stevehose]

I can't decide if I want the SherryBerg, the NENKUTEN, THUNDERMINGO or the VergasRetor It's all a matter of which decal would look better on the window I guess.

Yes, the same Chinese makers of the $20 disposable lawn mower carbs