Lotus Elan

Stripped out idle screw hole

PostPost by: zog » Tue Mar 18, 2014 9:48 pm

I have an issue with a Weber 40 DCOE that I am hoping someone can help me with. I have one carb where one idle adjustment screw hole is stripped out in the body of the carb. Not totally stripped out, just enough so that if I back the screw out 2 turns it pops the screw and spring out of the carb. I tried cutting down the spring but there is just not enough meat left in the body of the carb to keep the screw from pulling out.I was thinking of using a jam nut but that does not look right and makes it tough for adjusting the idle mixture.


Have you ever run into this and do you have any ideas?
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PostPost by: bill308 » Wed Mar 19, 2014 4:05 am

Zog,

Is it the idle mixture adjusting screw or needle valve that is in question?

Assuming we are talking about the idle mixture screw, if the thread in the housing is damaged, I think you need to replace the housing. I do not know if you can find a thread chaser to reform the threads in the housing sufficient retain the screw when under spring tension and prevent an air leak past the threads.

I think the best solution is to source a replacement carb, or carb body and new needle valve at the very least.

Bill
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PostPost by: robertverhey » Wed Mar 19, 2014 5:46 am

Any reason why a helicoil can't be applied? I assume it's metric, and these go down to some pretty small sizes.

As a temporary bodge, maybe some plumbers tape around the screw thread will keep it in place.

Robert
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PostPost by: rgh0 » Wed Mar 19, 2014 7:21 am

Loctite have a product that reforms threads in partially stripped components see link below. Good for relatively lightly loaded items like this, I would not use it on a conrod bolt :lol: . Worth a try as cheap and easy and if it does not work then I would try a helicoil after that. Aluminium foil wrapped around the screw thread may help as a temporary fix.

http://www.henkelna.com/adhesives/produ ... 7876355073


Weber also used two type of idle mixture adjustment screws. One with a long tapered point and one with a shorter point. I don't know what carbs used which version but maybe you have the wrong screw for your carb or maybe a change to the alternative style screw could help if it engages the body threads better

cheers
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