Reworking CV carbs...

[tkent02]

Couple questions, what size are the drill bits that come with the Dynojet kits? I see a 3/32" bit goes through the existing hole with only finger twisting, so I bet the hole was some metric measurement about the same as 3/32" So is a 1/8" too big? 7/64"?

Anyone else add a float bowl overflow tube to these carbs or am I the first Guinea pig?
Seems silly to fill my crankcase with gas just because some bone head at the EPA thirty years ago thought it was a good idea.

Drilling a hole in the bowl, inserting a brass tube, what would work best to seal it in? Solder?

 

[almarconi]

For our bikes its a #30 size bit (.1285). If you don't have this size, the 1/8" is pretty close. I'm assuming you want to drill your slide hole.

 

[Steve]

Anyone else add a float bowl overflow tube to these carbs or am I the first Guinea pig?
Seems silly to fill my crankcase with gas just because some bone head at the EPA thirty years ago thought it was a good idea.

Drilling a hole in the bowl, inserting a brass tube, what would work best to seal it in? Solder?

Can't help you with the drill size question, but I like your idea of the overflow tube.

To attach the tube to the bowl, I'm not sure that simple solder would do. Might try silver solder or brazing.

How much over the recommended fuel level are you planning on placing the top of the tube? Need to measure how far below the bottom of the throat the normal level is, then go up no higher than that level. I was going to suggest placing the tube somewhere at or just right of center, so it would not overflow so easily, but actually, it's while the bike is on the sidestand that you are most worried about overflowing. If you put the tube on the left side of the bowl, make sure it's high enough that the bike can lean on the sidestand without putting gas down the tubes.

.

 

[tkent02]

For our bikes its a #30 size bit (.1285). If you don't have this size, the 1/8" is pretty close. I'm assuming you want to drill your slide hole.

Thanks, I think I'll go 7/64" first, then try 1/8" so I can learn what effect it has. I think it just makes the slides lift quicker, is that correct?

How much over the recommended fuel level are you planning on placing the top of the tube? Need to measure how far below the bottom of the throat the normal level is, then go up no higher than that level. I was going to suggest placing the tube somewhere at or just right of center, so it would not overflow so easily, but actually, it's while the bike is on the sidestand that you are most worried about overflowing. If you put the tube on the left side of the bowl, make sure it's high enough that the bike can lean on the sidestand without putting gas down the tubes.

.

What I'm working is the top right hand rear corner, I'm thinking I'll just do the two outboard bowls so I can keep an eye on them and switch them out easily if it does not work.

Steve, it looks like I can get the tube about 5 -6 mm above the fuel level, and still not be as high as the venturi, even on the side stand. Hopefully any fuel will spill out my tubes before going into the engine or airbox, similar to how it works on the VM carbs now. I can see it needs to be perfect to work.

I'm also trying to find a piece of music wire or something 2.5mm in diameter to replace the stupid float pivots with. They don't need an interference fit except to sell more carburetors.

 

[salty_monk]

You won't notice that much difference.... I have run drilled ones with stock setup with not a lot of difference before...

Dan

 

[machinest]

Thanks, I think I'll go 7/64" first, then try 1/8" so I can learn what effect it has. I think it just makes the slides lift quicker, is that correct?




What I'm working is the top right hand rear corner, I'm thinking I'll just do the two outboard bowls so I can keep an eye on them and switch them out easily if it does not work.

Steve, it looks like I can get the tube about 5 -6 mm above the fuel level, and still not be as high as the venturi, even on the side stand. Hopefully any fuel will spill out my tubes before going into the engine or airbox, similar to how it works on the VM carbs now. I can see it needs to be perfect to work.

I'm also trying to find a piece of music wire or something 2.5mm in diameter to replace the stupid float pivots with. They don't need an interference fit except to sell more carburetors.

MSC sells stainless dowels in 2.5 Dia
www1.mscdirect.com
part# 41851817 for 24mm long many other lengths and it looks like you can buy them singularly

 

[mighty13d]

the 82 gn250 carb comes with a overflow tube built into it. and it's a CV style.

 

[Rudeman]

Couple questions, what size are the drill bits that come with the Dynojet kits? I see a 3/32" bit goes through the existing hole with only finger twisting, so I bet the hole was some metric measurement about the same as 3/32" So is a 1/8" too big? 7/64"?

Anyone else add a float bowl overflow tube to these carbs or am I the first Guinea pig?
Seems silly to fill my crankcase with gas just because some bone head at the EPA thirty years ago thought it was a good idea.

Drilling a hole in the bowl, inserting a brass tube, what would work best to seal it in? Solder?

Have you looked at getting some bowls off of a pre-EPA Yamaha XS1100? They used the same carbs and I'm pretty sure they were equipped with bowl overflows.

 

[tkent02]

Have you looked at getting some bowls off of a pre-EPA Yamaha XS1100? They used the same carbs and I'm pretty sure they were equipped with bowl overflows.

Thanks,
I'll check into it.

 

[Guest]

Drilling a hole in the bowl, inserting a brass tube, what would work best to seal it in? Solder?

If you still go that route, I think soldering is your best bet. You can scribe the tube with the correct length you need when you solder it in; also, you can re-solder it if you need to adjust the length a bit - that wouldn't be possible if it was epoxyed...