Kate's MG, Part 7

In Part 6, we learned that the front carburetor had an incontinence problem - it wanted to run gas out the front! That's almost always a problem with the float or needle valve, so I pulled the carbs one more time:

John Zimmerman volunteered once again to help hold them while I did surgery. We only worked on the front carb, and spent a frustrating two hours trying to figure it out. We expected the float to be full of gas - that's why they usually can't stop the flow into the carb, because they are too heavy to float. But it was fine, and the needle valve worked fine too. If we tested it by hand, we could easily stop the flow. But if we reassembled the carb and tested it in the car, it behaved badly. One time it wouldn't stop flowing, and the other it wouldn't flow at all!

After two hours, reeking of gas and needing to get to other things, we called a halt. But I hate it when I can't understand a problem! It makes me sleep poorly, but often when I wake up, I have a plan of action. I literally "dream" myself into the next step.

Here were the problems:

1. Even with two guys, we were juggling the carb, the hoses and the fuel supply, and unsuccessfully trying to keep from dousing ourselves. At one point, John had gas dripping off his elbow!

2. The carbs don't have a single flat surface that is useful for keeping them steady when working on them.

3. The gasoline was stinky and dangerous, and a couple of times the effort to keep it from spilling actually made it spill.

So, I decided to take a hour this afternoon and make this:

Yep, it's a carb stand, just like the real live pros have. I even made it so the carb could be rotated 360 degrees for access on all sides:

That was a lot of fun to make, because excepting for the spacing for the two screws that hold the carbs in place, there was no measuring at all. I just picked a spot and drilled. Threads are tapped right into the wood. Of course, I would have made this 100% of metal if it was something I wanted to use over and over, but I've already figured out I'm not going to have a new hobby rebuilding SU carbs.

I put the rear carb, the one that works, on the stand and removed the bottom plate. I wanted to see how far the float hangs down in its normal position. Here's what I found:

We had been wondering about the float in the front carb, because it only moved a little. I suspected that was what was hanging things up. Sure enough, putting it on the stand, I could see that the float barely dropped:

So the next step is to find out why. I ran out of time today, but next time I get into the shop, I'll compare the two carbs more closely. I also have a scheme where we can test the float action on the stand using isopropyl alcohol instead of gas. That will smell a lot better, and not be a fire hazard.

One more interesting photo for now. This time when I removed the carbs, I dropped one of the nuts, and in retrieving it realized that there was a low spot that had accumulated a few others. Not really reachable when the carbs were in place, this is the rusty record of 43 years of dropped screws, nuts and washers!

Continue on to Part 8...