Float Height for Mike's/Aftermarket Floats

[MNiceGuy]

I recently rebuilt the BS38's on my '71 XS650. I sourced a couple of kits as well as 2 new floats from Mike's.

The jets and gaskets went in easy and seem to be doing their job. The floats on the other hand have been giving me some grief. Both were bent and one leaked right out of the box. After ordering some more I now believe I have two mostly-straight and gas-tight floats in there.

If I set the float height to 24mm I can all but guarantee at least one of the carbs is going to puke gas as soon as the petcock is flipped on. While researching, I landed on 2M's very, very detailed examination of the aftermarket floats: 2M's Original Thread

Based on his findings, I raised the float level to 28mm to compensate for the physically smaller aftermarket floats. The gas no longer overflows, the bike starts right up, and seems to run just fine.

Obviously the clear-tube method would be useful here but I still need to get a barb for the bowl. I'm curious, has anyone else encountered this?

 

[jpdevol]

Unfortunate experience. If you continue to have issues with those floats, there are other suppliers. Based on a recommendation from 5Twins, I just now received floats from Summit Racing (they look and measure as original) for a late-model BS38 restoration on carbs from DogBunny (nice carbs, w/limiter caps in-place).

https://www.summitracing.com/parts/mku-vm24-171 ......good price!

 

[MNiceGuy]

Unfortunate experience. If you continue to have issues with those floats, there are other suppliers. Based on a recommendation from 5Twins, I just now received floats from Summit Racing (they look and measure as original) for a late-model BS38 restoration on carbs from DogBunny (nice carbs, w/limiter caps in-place).

https://www.summitracing.com/parts/mku-vm24-171 ......good price!

You say these are for "late-model BS38" but I have a '71 so I'm not sure if what I have is the same as what you're working on. Is the float the same across all BS38?

Edit: I checked parts fiche and both a '71 and '79 call for Yamaha Part# 256-14985-00-00. It would seem they're the same.

 

[5twins]

Yes, all BS38 floats are the same, and they're nothing special, just plain jane Mikuni VM24-171 floats. Retail on them is only about $15 but you can often find them discounted, like from Summit.

 

[MNiceGuy]

Unfortunate experience. If you continue to have issues with those floats, there are other suppliers. Based on a recommendation from 5Twins, I just now received floats from Summit Racing (they look and measure as original) for a late-model BS38 restoration on carbs from DogBunny (nice carbs, w/limiter caps in-place).

https://www.summitracing.com/parts/mku-vm24-171 ......good price!

@jpdevol - Just to follow up on this - I ordered a pair of the floats you suggested and it was immediately apparent they were closer to the originals than my Mike's versions. I set the float height to the normal 24mm and now all is well.

REALLY appreciate the tip! This was starting to get a little frustrating.

 

[jpdevol]

And thanks to 5Twins! I got the tip from him. And Summit is fast!; they must work 24/7.

Glad it worked

 

[5twins]

I'm really surprised no one discovered this sooner. Folks have been over-paying for BS38 floats for years, lol.

 

[atom4488]

I'm really surprised no one discovered this sooner. Folks have been over-paying for BS38 floats for years, lol.

I'm glad to have leaned of this, but shipping costs to Canada turn these $11 floats into $24.50 floats...plus I gotta wait 10 days to get them. I think I'll take my chances with the CruizinImage parts...

 

[5twins]

You'd best read up on them. Since the float "bulbs" are a different size, the stock float setting measurement will no longer work. You'll need to figure out a new setting to get the fuel level in the bowl correct.