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-   -   Plastic Carb Button Repair (https://www.goldwingfacts.com/forums/10-reference-faq-forum/500633-plastic-carb-button-repair.html)

Bronko37 04-24-2014 02:12 PM

Plastic Carb Button Repair
 
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Well here we go. I am sure every one is tired of hearing all the ways to "patch" these buttons. Well, I am developing a permanent solution. I am going to fully machine out the button and machine a new button to adhere to the remaining section that will stay rolled in the cap. There is no reason to remove that section as it is supported by the rolled metal any way. I have created a fixture that will allow me to hold the cap without damaging it. I machined a pilot bore to mate with the pilot diameter of the CV cap. I machined the pilot diameter to the same sizes as the carbs to create a mounting surface identical to where the cap sits on the carbs. Here are some pictures of what I have so far. It would be cool if we could make this a sticky while I go through the process. I will keep you updated and take pictures as I go through the entire operation. I am experimenting on one. If it works out, which I know it will, I will do my whole rack. I reverse engineered the broken cap button so I will be able to make it exactly like factory internally so we dont corrupt the vacuum. I also think Im gonna do the buttons in Black so you know they are custom. Let me know what yall think.

mh434 04-24-2014 03:08 PM

NICE!! This is a great idea!

BTW - that looks like a South Bend lathe...I'm a big fan of 'em. I have a '47 SB 9" that I use daily, and love it enough that my wife is jealous of the time I spend with it...:bow:

AZgl1800 04-24-2014 05:24 PM

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somehow, the thread got stuck :-)

Bronko37 04-24-2014 09:58 PM

It is a south bend 13". I have twelve of them....in the hight school machine shop class i teach. Along with 6 bridgeports. Im real spoiled when it comes to workin on these old bikes

rayworx 04-25-2014 10:07 AM

It is so great that there is still some schools that realize that there's a future for our kids in something else than just computers. My son has a degree in 3D animation but can't find a job in that field. Seems that he's got to 'know somebody' to get into the trade.

Bronko37 04-25-2014 02:11 PM

Day 2 -- Caps are easy to smash
 
7 Attachment(s)
Well day 2 went well until I destroyed my cap. I got a little carried away with the dead blow seating the new button into the cap. However, I did come up with a solid plan. Good thing I purchased an entire second carb rack so I have 3 more caps to play with.

Once I fully removed the original button I determined that there would be enough "meat" left to make a cap out of aluminum and give it a .001"-.002" press fit. Then, once the new button is installed I will cut the external profile in the fixture that I made on the lathe.

Here are some photos of my progress. Also, what not to do as I completely smashed my cap, lol.

I was able to check how well my button was adhered and check that the vacuum port was working properly so it is not a total loss.

OnaWingAndaPrayer 04-25-2014 06:46 PM

I like how this is shaping up . Sorry you lost the first cap but learnig is not always inexpensive . So if I understand after the "button" is pressed in then you go back to the lathe and finish the outside . Nice . I bet you could even do a set with spikes for a real custom look .

A thought to offer . Being aluminum , I would think ( thats dangerous) you could get the .002 fit and not have to force it . I think you could warm the cap enough that the button could drop in . You could freeze the button if you needed just a bit more fit clearence.
Looking good .

Bronko37 04-25-2014 07:33 PM

Gotta be careful with that though. There is a little rubber gasket that is under the button. I warmed it initially. Then i applied glue. I had a student make the button, trying to make a learning experience out of it. The kid hit the size perfectly, +.100", lol. At that point i had glued the gasket down so i didnt heat it the second time. .002" was easy to tap in and it held real solid. I just got over zealous trying to make sure it was all the way down. Totally my fault. Shoulda never happened. Damn thing was already in. Two taps.

The glue is almost like a lubricant. But then it dries solidly. I'll get the next one right you can bet on that. Now i just gotta get another cap for my spare set.

Bronko37 04-25-2014 07:36 PM

Quote:

Originally Posted by OnaWingandaPrayer (Post 3167785)
I like how this is shaping up . Sorry you lost the first cap but learnig is not always inexpensive . So if I understand after the "button" is pressed in then you go back to the lathe and finish the outside . Nice . I bet you could even do a set with spikes for a real custom look .

A thought to offer . Being aluminum , I would think ( thats dangerous) you could get the .002 fit and not have to force it . I think you could warm the cap enough that the button could drop in . You could freeze the button if you needed just a bit more fit clearence.
Looking good .

I am wondering how it will hold under heat. Another thought i had was to cut a tiny v groove at the split line where the button and the cap meet. I could then lay a thin bead of solder for a more positive hold. A little more effort but may be necessary. I could polish or turn away the excess easily on the lathe. You would never see it.

Thoughts?

OnaWingAndaPrayer 04-26-2014 08:20 AM

Let me turn this another direction . As a teaching/learning project ,what is the possibility of threads ? Maching the old button out . Cut SAE (?) threads and screw the new button in place with loctite and then the final machine work .
Another thought: Is there enough depth/meat to cut an O-Ring groove in the button instead of the rubber gasket under the button .

Back to heat , I am only thinking of say toaster oven at 150-200 degrees . If the rubber gasket could be glued to the frozen button - no heat damage .

I dont know if you can get solder to adhere to aluminum . But as reread your thought of cutting a groove....If the groove (half depth groove) was cut in the button and corrosponding (other half) groove in the cap , Then flow solder in to fill the groove and it would be locked in place . It wouldnt neccessarily need to adhere to the aluminum.

I may yet have to take one of my broken ones apart to study this .


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