Technical Carb Flange Bowed - Now what?

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Technical Carb Flange Bowed - Now what?

Texas500

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The motor on my 500D has been giving me problems. It starts and runs fine when cold. Once it hits operating temperature it runs for about 10 minutes then quits and will not start. If I wait 10-15 minutes it starts right up. I pulled the carb and found the flange to be bowed. Enough so that is rocks on it's axis when placed on a flat surface. The carb spacers also has a few cracks.

What's the best way to straighten the carb flange?
 
Being aluminium, the likelyhood is that, once you start to manipulate it it will break off. Is it actually bent up or is it just a knock? A picture would be good. I would first be concerning myself with finding out how it happened and then going from there
Damian
 
It has a slight downward arch (bending down at the bolt holes). I probably overtightened the carb nuts at some point. I'll see about getting a photo.
 
You need a sheet of glass, or some other flat surface, a sheet of sand paper and a lot of patience!
 
Hi I have rebuilt quite a few Weber 26IMB and 28IMB carbs over the years and most have a bow on the flange to some degree but the 26IMB carbs are by far the worse as they have a less robust flange. The carb bodies are made of a zinc based alloy I believe, a bit brittle but they do have a bit of give so I tend to strip the carb and put the carb body in a large vice with plain jaws against the flange and body top and tighten the vice to straighten the flange. Either that or nip one side of the flange in the corner of the vice jaws then tap the carb body with a soft mallet to take out the bow then repeat with the other side. I then finish off with with a new sheet of 150 grade wet or dry paper on a sheet of glass or flat board holding the carb body down firmly just above the flange making sure that it does not rock. Also check the carb spacer then use new gaskets. You may also find that the carb top cover has distorted and I have also straightened those out with a little gentle persuasion :)
 
Thanks Toshi. Exactly what I needed to know. Hopefully this will fix my problem.
 
I've not seen one that bad before. Toshi's idea is the best and most likely to solve it
 
I agree with the preceding suggestions but I wouldn't want to take a chance of causing fatigue on the metal.
Another option, which would be reversible, would be to build up the flange with epoxy steel such as "JB Weld".
With a temporary gasket made from greaseproof paper or thin plastic on top of the head to stop the adhesive from sticking and some cling-film around the studs you could put on a generous wipe of the epoxy on the base of the flange and tighten the carb to the head very gently, remove the excess and let it set.
When removed you might still need to resurface the epoxied flange and tidy it up at the throat of the carb, but rather than weakening it you will have added some strength.
 
A friend of mine stopped by today to pick up the carb. He is taking to his machine shop for resurfacing :) Btw, we also found the carb spacer was warped. Looks like air was entering the motor above and below the spacer.
 
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