Help: Installed deptch of 4A1 needle valve SEAT - PeachParts Mercedes-Benz Forum

wolf_walker · #1 12-09-2009, 09:21 AM

I'm still chasing silly problems on this thing. Awhile back the seat came loose in the casting, I tapped it back in only to find there was no stop and one could merrily tap it down to nothing. I raised it back up and I can't remember how I determined how far up was correct, I might have guessed. I'm chasing what still seems to be a float related flooding issue at extended hot idle and a hard hot re-start and I keep coming back to the float assembly, but cannot find fault with it. Does anyone know or have one handy they can measure how far above the base the float needle seat sits on one of these? It would be much appreciated.

Rick76 · #2 12-09-2009, 06:21 PM

Service Information Bulletin dated January 1981 (Ref No MBNA 07.2/1) states that you drive it down to stop with a special tool. Unfortunately they don't give dimensions so you can make your own.

It reads:

Subject: Replacement of Seat for Float Needle Valve, Solex 4A1 Carburetor

In some instances it is possible for the needle valve seat to work itself loose and travel upwards. The consequently lowered fuel level may result in complaints such as rough, erratic engine operation due to fuel starvation at full throttle operation. In the past, this necessitated carburetor replacement which is no longer required because repair-size needle valve seats are now available. Replacement of a needle valve seat is mandatory.

Work Procedure:

1. Pull needle valve seat from carburetor body after removal of the float.

2. Measure valve seat counter bore with the go-no go gauge and determine the repair size.

Note: The single grooved end of the gauge indicates a fit for the 1st repair stage, and likewise, the double grooved end corresponds to the 2nd stage.

3. Carefully drive the new needle valve seat down to the stop with the special punch. Be sure that the needle valve seat is installed exactly perpendicular and that the fuel inlet port is positioned as shown in illustration 1.

Note: An installation tool kit which contains the go-no go gauge and special punch is available from you local parts depot.

4. Adjust float level

Spare Parts and Tool Information

Float needle valve seat 1st repair stage 000 071 01 94
Float needle valve seat 2nd repair stage 000 071 02 94

Valve seat installation kit 000 581 00 80

wolf_walker · #3 12-09-2009, 06:36 PM

That figures. Thank you for the info though.

I actually have two carbs, but I can't remember which one I had to re-seat the seat in, I think it was this one. But knowing me I experimented on the one that wasn't in the car and I had no idea the seat would just drive on away to oblivion so I didn't measure.

If anyone has one apart handy a quick measurement would be wonderful.

wolf_walker · #4 12-10-2009, 12:20 AM

Well I think the seat was low, it broke trying to raise it. Surprise surprise.

t walgamuth · #5 12-10-2009, 06:19 AM

IIRC, if the needle is riding too high it will run rich, too low lean. If you feel it is running rich (black cmoke) you would need to adjust the needle deeper if possible or raise the seat.

If it is running too lean it would buck on attempted acceleration I think.

wolf_walker · #6 12-11-2009, 11:20 AM

Interestingly there are a couple of seats on ebay, go figure.
Lacking the tool and having spent countless hours on this ill designed and mistreated pair of carbs, I'm going to look the other way.

silverteam · #7 12-11-2009, 04:31 PM

25 years ago when I turned wrenches, we had the same problem. The car was towed in and the float seat came up and shut off the fuel. We just took the top off the carburetor and punched the seat slightly down to the original position, with the center punch we tightened up the float seat. After this was done, we reinspected the float adjustment. You put the float in the original position with your hand, it should be 2-3millimeters under the surface where the gasket goes. We had to do this repair 20-30 times for different customers over the years.

wolf_walker · #8 12-11-2009, 06:27 PM

Quote:

Originally Posted by silverteam

25 years ago when I turned wrenches, we had the same problem. The car was towed in and the float seat came up and shut off the fuel. We just took the top off the carburetor and punched the seat slightly down to the original position, with the center punch we tightened up the float seat. After this was done, we reinspected the float adjustment. You put the float in the original position with your hand, it should be 2-3millimeters under the surface where the gasket goes. We had to do this repair 20-30 times for different customers over the years.

Pretty much what I did, think I got it a hair low though. Hard to say.
I can't imagine what possessed them to PRESS a seat in like that, not even swedged, just pressed.