Weber 40 IDF - Throttle Shaft Slop

[dtrumbo]

Hi all,

So the dual Weber 40 IDF's on my wife's bus have been the bane of my existence. I now believe I have discovered a possible explanation for the continual middle-finger I seem to receive from them. The symptom is after the bus warms up, the idle floats high. When in this mode, you can tell the left (3/4) carb is not at its idle stop. If I manually move the linkage against the stop, the idle returns to normal as one would expect. I disconnected the linkage completely to remove that from the mix and by manually opening the throttle on this carb and then letting it close, it does the same thing... not close all the way. The right carb (1/2) returns to the idle stop as expected. I decided to pull this lazy carb and inspect it to see what's what. Here are some pictures and even a little video of what I think is a problem.

Using the accelerator-pump linkage piece in the center as a reference, with the throttle closed, that linkage is more or less centered in the body.


With the throttle open, the torsional tension of the return spring actually pulls the throttle shaft toward what is the left side of this photo by a fair amount.


Since it's not nearly as obvious in these photos as it is in real life, I took a little video of it. Here you can see while holding the throttle open, I can move the shaft laterally quite a bit.
http://s289.photobucket.com/albums/ll23 ... V00011.mp4

Is that much slop normal? My guess is that slop isn't supposed to be there and the throttle shaft moving left on throttle-open is causing some binding on throttle-close that's not allowing it to completely close. I'm thinking something is seriously worn out, but before I try to throw parts at this thing (so far I've only found the bearings for the throttle shaft), I thought I'd get some Weber-experienced second opinions.

Thoughts?

[dtrumbo]

Proving the point that all good things must come to an end... Mark Harney appears to have closed up shop. I was smart enough to download the cleaning, float adjusting and synchronizing pages from his website before it vanished, but wasn't smart enough to download all of it or God forbid, remember what it all said.

I'll keep digging... maybe someone smarter than me has archived it somewhere.

Thanks, Jim!

[Amskeptic]

Obviously, some pretty sh*tty manufacturing...

The only reason I push oem engineering, it is why my dignity is largely intact.
Colin

[dtrumbo]

As usual, Jim, your crystal ball is perfectly tuned. That's exactly the issue I have. The left carb (right one seems fine) has eaten itself by having the return spring on the other side of the body as the actuating linkage. Look, more photos!

Here it is all disassembled.


On the return-spring side, there are two washers, one on either side of the bearing.


On the other side (linkage side for a left carb) there is only one.


So my first thought is somebody lost one the last time they had it apart. Nope. The multiple exploded views I've found show only one washer on that side of the carb. As predicted, the wallowing around of the throttle shaft has worn perfectly round throttle plates into egg-shaped-with-a-notch dog tags (that's the only use for them I can think of).




The pictures don't show it as well as your eyes can see them in person, but the story is the same, they're ruined.

So... as luck(?) would have it, I bought a brand new IDF 40 body for $75 that has all brand new parts in the places where mine aren't new at all anymore. That combined with the gajillion bits and pieces from my old carb will make a new one again.

Jim, I just found the Web-link in CB's catalog. I'll be ordering one and will put it on my 'new' left carb to hopefully prevent the untimely death that current carb experienced. Thank you a million times for that info. Otherwise, I would have just gone back down the same insanity-defining road. I think I'm up to owing you about a pony keg's worth of beers! I truly hope to meet you someday to attempt repayment!

[dtrumbo]

So I received my new carb body, completely disassembled it, soaked it in cleaner overnight and put all of the parts from my old carb (except for the worn-out throttle shaft, plates and bearings) on it. I also installed the "web-link" throttle spring reversal kit (to make it a lefty instead of a righty on backwards) http://cbperformance.com/catalog.asp?ProductID=551 , and now I have a very smooth, mostly new carburetor. Wow, what a difference.

BTW, for anyone going down the take-apart-your-Weber-and-put-it-back-together road, DON'T OVER-TIGHTEN THE THROTTLE SHAFT NUTS! If you do, you'll stroke-out when the "new" carb has a stickier/stiffer throttle response than the old one. A touch over finger tight with the lock tab folded over is fine. Another note, the axial slop when the throttle is fully open is normal. What isn't normal is any kind of binding or "stickiness" when you open and close the throttle.

Here's a pic of the final product.


Sorry I didn't have time to take more step-by-step photos, but I was a little under the gun. You see this is my wife's daily driver and since I had it all apart, she has been driving our very tired Riviera doing the carpool thang. On final re-assembly day I ran out of Gumout (the HORROR!) and had to run the the hardware store to get more. When I started the Riviera, the asynchronous starter-sound told me that #1 cylinder has finally had enough. I babied him to the hardware store and back with the promise that this would be his last trip (this time for sure, Rock!) before some serious engine attention. Of course, he complied, but that meant no time for dilly-dallying getting the carb back on, half-assed synchronized and on the road. You'll see more soon in the other forums.