Planning on single carb conversion over winter

[NeopolitanSliceCream]

Planning on single carb conversion over winter.

Was thinking of building my own manifold, I'm a fabricator.

Might go with this plate from The rebel spirit, and build off of it to fit my frame.

What kinda carb should I run? I want mechanical.

And anything else I need to look for, or know, before attempting ? Thanks

 

[grouchie77]

I built my own, using one of the BS38s that came with the bike. I could never get it tuned properly though. I had to use the choke when stopped, but when I was up to speed I had to reach down and flip the choke off.

 

[NeopolitanSliceCream]

Ah okay. Good to know thank you I think the vaccum carb might be part of the issue there. I also might do a dual carb conversion and just get some VM mikuni's but I'd still need a custom intake for them because of my frame.

Any chance you have an idea where I could get just the plates that you used to mount the intake? I'd rather not make my own plates.

 

[Highpower]

First off, when you do build your manifold, center the carb so the intake runners are the same for both cylinders. Theoretically, you could get by with a carb the same size as a stock one, but as a practical matter I would go up one size from say, a 38mm to a 40mm. The trouble with a XS is that there is no room to do a center carb as they engineered the frame with the backbone running right between the cylinders, leaving you with a packaging issue for installing an air filter. That is why the XS uses what is in essence two air boxes. IMO pod filters are garbage and should be avoided at all costs.

My choice of carb regardless of the bike, is always going to be a flat slide Mikuni. Back in the day when I was still mechanicing for a living, I put a ton of flat slides on Harleys where the owner had done performance modifications and they need a bit more intake flow. I put one on a '87 FXRS I built for myself out of a totaled bike. I shaved the heads .050", installed a new cam and did a few other things to it. That bike was quick and fast and reliable as a stone. I made three trips from California to Sturgis with zero issues. Once I got that Mikuni dialed in, it never needed any sort of adjustment.

 

[grouchie77]

Ah okay. Good to know thank you I think the vaccum carb might be part of the issue there. I also might do a dual carb conversion and just get some VM mikuni's but I'd still need a custom intake for them because of my frame.

Any chance you have an idea where I could get just the plates that you used to mount the intake? I'd rather not make my own plates.

Nope; I machined my own out of 6mm thick 304 stainless.

 

[grouchie77]

There is a website called SendCutSend. A few users here have tried them.

I just for a quick reference uploaded a STEP file of my design of my intake plate and it looks like for less than $30 I could get one out of 1/4 thick 304 stainless.

You might also be able to see if a local welding shop or machine shop could make the flanges.

I'm interested to see if this works for you since I might learn a thing or two on how to dial in my single BS38.

 

[Kevin Kruse]

@grouchie83 Interesting carb support, took me a second to figure it out, I like it. CNC’d or manual?

 

[grouchie77]

@grouchie83 Interesting carb support, took me a second to figure it out, I like it. CNC’d or manual?

View attachment 354249

CNC. 3D printed a few prototypes before I was happy with the design and ready to make an aluminum version.

 

[grouchie77]

Bolts to one corner of the carb using a longer cap screw, and a pair of set screws clamp the bracket to the sidecover bracket. The U-shape acts as a tension spring and keeps the carb from falling out of the boot.

 

[grouchie77]

There is a website called SendCutSend. A few users here have tried them.

I just for a quick reference uploaded a STEP file of my design of my intake plate and it looks like for less than $30 I could get one out of 1/4 thick 304 stainless.

You might also be able to see if a local welding shop or machine shop could make the flanges.

I'm interested to see if this works for you since I might learn a thing or two on how to dial in my single BS38.

After re-reading this I thought that there is a chance it might cause some confusion.

I uploaded a single 1-piece flange to that SendCutSend website, even though my intake has 2 individual flanges. Hope this clears up any potential confusion.

 

[Jim]

I uploaded a single 1-piece flange to that SendCutSend website, even though my intake has 2 individual flanges. Hope this clears up any potential confusion.

Perhaps you could upload the CNC file for that plate? Then anyone could send off for one.

 

[grouchie77]