Jump to content
Sign in to follow this  

Another Carb Question

Recommended Posts

I've been sniffing on replacing the stock carb on my 01 XR400.  I have read posts dating back 5 to 6 years on the subject which include MANY different makes,  models and sizes.  Given the time and effort people have put into researching this topic I'd like to come a consensus on what's the best offerings right NOW (Fall 2013) with respect to .......


1.  Improved Starting

2.  More performance

3.  Future Big bore kits




Thanks in advance for everyone's thoughts.

Share this post

Link to post
Share on other sites



Mikuni 36 Kit




FCR ??


Mikuni 36: Works decent for stock bore, expensive

BST40: Works good for stock bore, inexpensive, but needs quite a few mods to install properly.

BSR42: Works good, big enough for big bore, inexpensive, needs a carb spacer and a few minor mods to fit properly.

TM40/HS40: Probably a bit big for a pumper carb

FCR: The ultimate carb but you will need to hack a lot of things apart to fit it.


As far as starting, all of the carbs are easy to start.

Edited by mudguy

Share this post

Link to post
Share on other sites

The Edison Approach here might have what you need. Lots of posts.

(if someone can do a summary and add it to the FAQ as a post, that would be great.)

ADV Rider is another source for info.


Some wrote that he installed a FCR off a WR250 and it worked great, but never shared the jetting specs. A friend of mine installed a FCR39 and it ran great, but was a nightmare setting up the jetting from what Sudco sold him. The bits you may have to jet correctly are, main jet, needle jet, needle (in various tapers, raise or lower), pilot jet, fuel screw, accelerator pump screws.

Jetting tips (FCR for Yamahas)


If you shop for used FCR carbs from 250f bikes, do some research first. The carb size used varies between the MX and enduro bikes and between companies. Honda ran larger carbs than other companies on their CRF on some years.

Length, height, and opening sizes all come into play. If you find a great carb, please share the specs.

Edited by Kev_XR

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this