Mikuni conversion for Honda XR500
Turning ponies into horses
There is nothing wrong with the Keihin 36mm carburetor. It does its job very well for a very long time. It just needs a new air cut-off valve every 30 years or so...
However, if you want more oomph out of your XR500, fitting a Mikuni carburetor is how you get will the most bang for your bank!
Once you have started playing with less restrictive exhausts, then you really have to fit a Mikuni anyway to see the bike's behavior get transformed.
Do not get into hot cams, high comp pistons and head porting before you have fitted a Mikuni carb, this would be putting the cart before the horse.
I like to tweak my XRs with period parts, so I stay away from the more performant and modern set-ups such as flat sides and accelerator pumps. A good Mikuni VM 36 or 38mm round slide keeps it all the way it would have been back in the day.
Now the best source for a Mikuni VM is one that come from a 2 strokes bike. BUT, the settings of a 2 strokes are VERY different from what a 4 strokes needs.
Genuises and magicians have spent years testing and refining the settings to make a XR500 roar. I took a simple route to get my settings right.