Author Topic: Mikuni carb swap  (Read 2008 times)

scottly

  • Full Member
  • ***
  • Posts: 149
  • Humboldt, AZ USA
Mikuni carb swap
« on: June 11, 2015, 09:52:06 PM »
The 36mm Mikuni has a 1.7" OD spigot on the engine side, while the FT carb has a 1.84" OD. I machined an adapter to mate the Mikuni to the FT rubber manifold with a short piece of radiator hose. The adapter moved the carb back about .4", which allowed for a gentle bend under the gas tank for the throttle cable. For testing purposes, I robbed the throttle and cable off my CR480.

scottly

  • Full Member
  • ***
  • Posts: 149
  • Humboldt, AZ USA
Re: Mikuni carb swap
« Reply #1 on: June 12, 2015, 07:29:17 PM »
The Mikuni has a larger OD on the air-cleaner side than the FT carb, so a new hose to connect the carb to the air-cleaner was needed. I found an air intake hose on a Ford pickup at the local junkyard for $4, and cut a section with the needed bend out of it. It was a bit of a stretch getting it onto the carb, but fit easily onto the air-cleaner that was supplied with the White Bros XR kit.

wrk2ride_ride2wrk

  • Jr. Member
  • **
  • Posts: 85
Re: Mikuni carb swap
« Reply #2 on: June 15, 2015, 04:57:41 AM »
Good stuff, be interested to hear how it responds when your done. I'll fit a 39mm FCR this week time allowing

thumperdh

  • Full Member
  • ***
  • Posts: 141
Re: Mikuni carb swap
« Reply #3 on: June 15, 2015, 09:48:48 AM »
Sweet, always wanted to do this but I could never justify it on my mostly stock motor.
1982 FT500
Conti Classic Attack tires
Foam filter mod
Round headlight
Rejetted carb
Progressive springs
Supertrapp muffler
Thumperstuff header

scottly

  • Full Member
  • ***
  • Posts: 149
  • Humboldt, AZ USA
Re: Mikuni carb swap
« Reply #4 on: June 16, 2015, 11:53:57 AM »
I rode the bike around town a little, and so far it runs fine, except for a slight hesitation while maintaining a steady speed at low throttle openings. It feels lean, possibly due to the needle clip in the highest groove? The lack of an accelerator pump isn't an issue; I had the bike lugging in 4th gear at about 30 MPH and snapped the throttle open and it just thumped right along. The choke lever is hard to reach when sitting on the bike, but no choke was needed with the outside temperature at 88 degrees.
Wrk, what is an FCR?

triguyracer

  • Jr. Member
  • **
  • Posts: 64
Re: Mikuni carb swap
« Reply #5 on: June 16, 2015, 03:50:40 PM »
 A fcr is a type of flattslide carb,your round slide MIK will work xclnt I had one on my yam sr500 when I had one in 1980 and it worked xclnt once jetted they work real good. Please post your jetting specs when you get it dialed in as it is one of the mods I want to do on my own ascot,round slide MIK can be found real easy, the costly part is having and getting all the correct jets ,needles ,recevers ,if you know the internal specs for them you can save quite a bit of money

wrk2ride_ride2wrk

  • Jr. Member
  • **
  • Posts: 85
Re: Mikuni carb swap
« Reply #6 on: June 16, 2015, 04:08:53 PM »
the Keihin FCR like the Mikuni you've fitted has a throttle cable to slide (flat) popular as a race carb, had a couple so just thought I'd try it out.
 :)

scottly

  • Full Member
  • ***
  • Posts: 149
  • Humboldt, AZ USA
Re: Mikuni carb swap
« Reply #7 on: June 16, 2015, 06:21:52 PM »
Looks like that FCR has a spool for the throttle cable the same as the stock FT. Let us know how it works; I'm a fan of the "I had one so why not try it" way of thinking. ;D

WTF304

  • Full Member
  • ***
  • Posts: 174
Re: Mikuni carb swap
« Reply #8 on: February 04, 2017, 12:58:29 PM »
I know this is an old thread but .... has anyone successfully used an FCR carb ? Or was it bust ...