Removing and installing throttle shaft on Bing carb

by Kyle S in 912 / 914 Technical Questions 7 years ago

When replacing the o-rings on the carb, the throttle shaft must be removed to install a new o-ring. In order to do this, you must remove two screws that hold the throttle valve in the throttle shaft (73-00-00, page 14 in the 912 parts catalog). Those screws have been peened over on the exit side of the screw See this video for a good visual explanation. When the screws are removed, they strip out the throttle shaft.

Throttle shaft: 963992
Throttle valve: 963666
Screws: 941200

(1) Is there any way to remove the screws besides grinding the ends off?

(2) Can I reinstall the screws with blue loctite or do I need to peen the ends over?

Re: Removing and installing throttle shaft on Bing carb

by Roger Lee » 7 years ago

Roger Lee

131 5.38k 5.44k

Here is a couple of things to try and I hope this helps.

I have found that if I take my small butane torch and heat the butterfly shaft around the screws many times they will just unscrew right out without any damage or issues. The peening just insures they won't come out by themselves, but with a screwdriver they will still come out many times. For the ones that are peened a little better you can either file the threaded side down or I use a Dremel tool with either a sanding drum or a grinding tip and just sand it down. The file may take a bit to do that, but the Dremel takes seconds. I still find heating the shaft around the screws at times helps in some removals. I don't use a heat gun because I can direct the flame tip off a small butane torch in the exact spot I want it instead of using a heat gun that heats everything. Doing these things this way I have never ever damaged a butterfly shaft. I would peen them vs Loctite because the downside is if the Loctite were to loosen at all under any heat and a screw comes out it is going into a cylinder and that fix will hurt your pocketbook.These screws aren't something you need to remove except during an overhaul which is far and few between.

When you put new ones in the peening process is very easy. I have a 6" piece of 1 3/8" round aluminum rod that I place straight up in a vice. That's a perfect fit to slide the carb down on top of and the screw heads and shaft rest right on top of the flat aluminum top for support. Then take a 6" flat headed drift punch and a hammer and place the punch on top of the screw ends and peen them over some. You don't need to get carried away peening them over.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Thank you said by: RotaxOwner Admin, Kyle S

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