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Discussion Starter · #1 ·
I'm attempting to try and fix a broken insert that I had on my GL1000. These caps are the same as the CB450 (at least on my K3). In fact, I pulled the one off my 450 to use on the GL1000 while I fixed this one.

Keep in mind, I'm not a machinist. I always wanted to be one and even got a degree in Machine Technology from a College in Portland, OR about 30 years ago. I worked as a Maintainence Machinist for a couple of years while I was in college but eventually got into the restaurant business in order to make my fortune.....NOT.

Anyway, I've got a cheap little Harbor Freight style table top lathe which works great for this type of work. I don't have much in the way of tooling though so I have to make do.

With that disclaimer, please offer up any suggestions as to how this might have been a little easier. I haven't tested the cap yet but will do so on the GL in a few days.

Here is the start, I just got a call from one of the restaurants and I have to run out and fix some equipment but I don't want to loose this text. I'll finish up the rest of the 10 photos or so later.

Here I chucked up the carb top making sure the jaws are covered so it doesn't damage the inside of the carb. It doesn't have to be tight since I won't be hogging out a bunch of metal.edit

 

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Discussion Starter · #2 ·
Ok, where was I before I was so rudely interrupted......oh yea, replacing white plastic inserts.

Using a lot of care, I took out as much material as I could without hitting the black material under the white cap. You can just start to see the black gasket iin this photo. Additionally, I took it out all the way to the "roll" of the carb top without hitting the top.


This is the what I was able to pick out after the lathe operation. The yellow part is what's left of the cap insert and the black gasket is what's under the plastic insert. The black piece is not rubber, rather it is some sort of fiberous material. I will reuse it for the new part. The old plastic insert had a little convex ridge around the bottom. This ridge sat on the black gasket and pressed into the gasket to better for a seal.


This is all the teflon material that I have so it will have to do. The other problem is that the stock has a small hole in the center that I drilled way back when I was making something else. I'll have to make due. I turned the stock down to 1.005". That allowed me to insert the part into the the carb cap with only a "thumb press". In this picture I've cut a shoulder 3/32". I "estimated" this width plus the thickness of the of the gasket would give me the total thickness I would need for a final fit.


Here is the part, with the gasket underneath, "thumb pressed" into place. At this point there is no laterial of vertical play. To remove the part I just used a punch from the oposite side to and tapped it out.
 

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Discussion Starter · #3 ·
I needed to cut a relief on the underside of the new cap for the carb slide. The carb slide protruded about 3/32" so that's how far I tried to counterbore it. I didn't have an end mill so I just used a 1/2" drill to start the hole. I then removed the drill and made a bottoming drill out of it and finished the cut. The final bore depth was a little more than 3/32". Becuse it's a little deeper, the insert will not act as a bumper anymore. It souldn't be a big problem but we'll see.


Here is the part showing the final bore. Additionally, I applied some dykem and inserted the part to show where the shoulder cut needs to be made. The shoulder cut is necessary so there is some clearence for the vacuum port in the carb top.


I've applied some more dykem to highlight the final shoulder cut. Here you can see the shoulder and the counter bore for the slide.


Here is the carb top with the black gasket in place. You can also see the vacuum port. In hindsight, I might not have needed the shoulder cut on the part since the thickness of the gasket would have give me adaquate thickness for the vacuum to be created. I don't think the shoulder cut should hurt things but we'll see.
 

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Discussion Starter · #4 ·
Here is the part in place. You can see the hole in the top of this prototype. In order for this to work the new insert has to be tight. I took a 1" socket and rounded it (on the lathe). It fit right over the round lip of the carb top. My intent was to use the socket as a die to re-seat the round bevel onto the shoulder of the new insert. I didn't want to use a press for fear of damaging the cap so, instead, I used the socket and gave it a couple of easy whacks with a ball peen hammer using increasing force and constantly checking to see that I wasn't damaging anything. In the end, I could still turn the new insert so I knew it wasn't tight enough. To get a tight fit, I grabbed a large drift and tapped the ridge lightly all the way around. I made 3 passes and that was enough to make it tight enough that I couldn't turn the new insert with my hand.


Next up was to chuck the cap back in the lathe and turn the new insert down to the shape I wanted. I could tell the insert was nice and tight when it didn't move or rotate while I was cutting it on the lathe. You can barely see the slight marks on the rounded portion of the cap that holds the insert. While it was chucked up I used a fine file to clean up any remaining marks from the punch. You can see the hole in the top. At this point I sure wish I had started with a new piece of Teflon stock since it was turning out so nice.


To take care of the hole, I tapped it with a 5mm tap and inserted a SS screw. I'll use a rubber O ring under the head of the screw to seal it up.
 
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