How Do I burr the Ends of the Throttle Shaft Screws?

[Guest]

I have removed the two screws from the butterfly and throttle shaft from a BS36mm carb. I have ordered new screws and was wondering how is the best way to secure them so they do not come undone in service.

The originals were burred over from inside the throat of the carb. As can be seen in the photos the heads of the screws are just inside the throat of the carb where it mounts to the head. To burr the screws over would mean reaching a long way inside the throat from the air cleaner side and hitting the threaded end of the screw with a punch of some kind. But I am worried that with such force I could possibly bend the throttle shaft and stuff things up.

Could I use Loctite or would fuel soften and dilute it in some way.

What other options do I have?

Thanks.







.

[tatu]

Might it be possible to make a sort of rivet snap? Drill a dimple into the end of a piece of metal to locate the head'v the screw to support the shaft, grip it in a vise and get an extra hand to hold the carb and use a punch to burr the screw thread over.
No harm in a bit'v loctite.
Or, even a crosshead screwdriver held in the vise supporting the screw.

[Nessism]

Some permanent type thread locker won't hurt. If you want to peen the screw too, I'd fashion some sort of insert to support the back side of the butterfly shaft so you don't bend it during the operation.

BTW Don, what led you to remove the butterfly(s)?

[hampshirehog]

You have to remove the butterflies on quite a few carbs if you want to pull them apart - keihins on sohc Hondas for example. Red Loctite is the answer - I've never lost a screw. Some of them came with the tiniest little tab washers that you bend over, as per your rear sprocket etc.

[Suzuki_Don]

Some permanent type thread locker won't hurt. If you want to peen the screw too, I'd fashion some sort of insert to support the back side of the butterfly shaft so you don't bend it during the operation.

BTW Don, what led you to remove the butterfly(s)?

Ed, the carb is a BDS36SS from a VX800 and there is an air leak around the throttle shaft seals, so I need to replace them. I have ordered the new seals and throttle shaft screws, but they have to come from Japan so will be a couple of weeks. Also I don't have the luxury of the carb dip you guys have in the US and I use the Yamaha carb dip and heat it up on a primus to a gentle boil to get the carbs clean and these seals don't like the temp of the solution. Rubber does not hold up as well as plastic like the ones in the GS carbs.





Thanks for the comments, I was just unsure whether the red Loctite would be affected by the fuel passing through the throat of the carb on it's way to the cylinder.

[JEEPRUSTY]

Those seal will eventually leak for all of us thanks for the pics DON
Nice to see someone who does a complete carb re-buil dand does not just talk the talk.

[chuck hahn]

Red loctite should be sufficient. If you really want to peen the threads then a round steel from the head side to act as the anvil. Then a sharp center punch to flair the threads will do. Set carb on the round stock and support so you can peen the screws..move on to the next carb till all are done. But there really should be no need to peen them.

[Suzuki_Don]

Thanks Rusty. I am not sure the GS seals are the same as the ones I have removed from the VX carbs, but it's not rocket science.

I have decided then that I will go with the Red Loctite, although I might buy a new bottle as the one I have would be about 10 years old.

Thanks for the comments and advice. That's what's good about this site, always a variety of comments and alternatives suggested by people on the site to choose from.

[JEEPRUSTY]

peening the tips should be eas I assume they are far softer stuff than the rod.
It is coll how the seal seems to almost bite into the shaft cutting a channel.

Maybe that groove is machined in and the seal is dynamic under vacuum, getting tighter under load and loose when shiut off?

[Suzuki_Don]

peening the tips should be eas I assume they are far softer stuff than the rod.
It is coll how the seal seems to almost bite into the shaft cutting a channel.

Maybe that groove is machined in and the seal is dynamic under vacuum, getting tighter under load and loose when shiut off?

Rusty see pics of the screws below, they don't appear to be made of a softer material than the shaft. They are steel and the shaft is steel.





Not sure how the seals work, but I am replacing mine as a matter of course. It is possible to replace only one seal without removing the shaft. But it is easier to get the seals out with the shaft removed.

[Nessism]

Back when I was working at Nissan they had a huge problem with butterfly screws coming loose and tearing up engines. They dicked around forever trying different fixes but most focused on different types of screws and threadlocker. And speaking of thread lock, there are a bunch of different types. When rebuilding my engine I used some high temperature medium strength Threebond stuff. My point is to make sure you get something appropriate for the environment, don't just blindly grab some general purpose stuff unless you check the application information. It would be worth a look to see what they recommend for use in a gasoline environment. Another thing is it's really important to degrease all the threads before applying the bonding agent, and give it plenty of time to set up.

Good luck and keep going...

[Suzuki_Don]

Back when I was working at Nissan they had a huge problem with butterfly screws coming loose and tearing up engines. They dicked around forever trying different fixes but most focused on different types of screws and threadlocker. And speaking of thread lock, there are a bunch of different types. When rebuilding my engine I used some high temperature medium strength Threebond stuff. My point is to make sure you get something appropriate for the environment, don't just blindly grab some general purpose stuff unless you check the application information. It would be worth a look to see what they recommend for use in a gasoline environment. Another thing is it's really important to degrease all the threads before applying the bonding agent, and give it plenty of time to set up.

Good luck and keep going...

Thanks Ed. Yes you are correct in every aspect. I need to do more research on the appropriate thread locker to use. The threads should be clean enough, the throttle shaft has already been through the Yamaha carb cleaning process and the screws will be new ones, I will spray them off with carb cleaner to remove any protective coating and all should be good.

Thanks again.