CRF CArb on a XR

[sage]

Hi All anyone put a CRF 250/450 carb on a XR400, if so how did it go any major headaches ??

[Perc82]

The MX carb from a CRF450 is way too large to fit in a XR400. Cutting and welding on the frame "WOULD" be required!

That being said... I have ridden on several different carbs on XR400's (Pumpers included) and the 42mm Mikuni CV carb (Polaris 500) has proven to be the best carb for a 400. It will bolt up with very little resistance. Just get it jetted out and enjoy the performance. ?

[sage]

Hi

Thanks for the reply, did you try fitting the CRF carb on your bike? just looking at the 2 different carbs ( well I have a CV 40mm ) the CRF carb looks smaller and more compact.

[JoeBlow Kokomo]

I've read several write ups of using crf250 carbs on 400's.

[vascoribeiro]

The MX carb from a CRF450 is way too large to fit in a XR400. Cutting and welding on the frame "WOULD" be required!

That being said... I have ridden on several different carbs on XR400's (Pumpers included) and the 42mm Mikuni CV carb (Polaris 500) has proven to be the best carb for a 400. It will bolt up with very little resistance. Just get it jetted out and enjoy the performance. ?

But the one you talk, the 42 is best for big bores right? The stock engine showld use the mikuni 40 from the ktm lc4 or suzuki dr 650 right?

I cant get any answer in the edison post

[KevinsXR]

I will still probably do the 36mm pumper kit from XRs only.

[ickfinger]

why the hell would you wanna do this swap. They use jetting/maintaining FCR's as an alternative to a jail sentance in some countries!!!!!!!!!!!!!!!!!!

[JoeBlow Kokomo]

why the hell would you wanna do this swap. They use jetting/maintaining FCR's as an alternative to a jail sentance in some countries!!!!!!!!!!!!!!!!!!

Cuz it's a pumper carb and everybody wants one. ?

Edited July 9, 2013 by MindBlower

[Kero]

I have the FCR MX 37 mm carb off a WR 250F on my XR. It runs superbly and punches out fourth gear wheelies with a 39 tooth rear, 15 front, on a 416cc motor with stock cam.

Once it was jetted it needs no adjustment apart from a seasonal tweak of the fuel screw.

[firstplacephoto]

why the hell would you wanna do this swap. They use jetting/maintaining FCR's as an alternative to a jail sentance in some countries!!!!!!!!!!!!!!!!!!

I put a 39mm fcr carb on my tt500 flattracker 10 years ago. Took it off my 2000 wr400 and just tweaked the jetting a little. Been a joy since,so much better than a 38 mikuni,better all the way around powerwise and starts one or two kicks,whether it sits for 10 minutes or 10 months!

[ickfinger]

I put a 39mm fcr carb on my tt500 flattracker 10 years ago. Took it off my 2000 wr400 and just tweaked the jetting a little. Been a joy since,so much better than a 38 mikuni,better all the way around powerwise and starts one or two kicks,whether it sits for 10 minutes or 10 months!

You must be very good with keeping carb dry while not in use!

[Kev_XR]

I have the FCR MX 37 mm carb off a WR 250F on my XR. It runs superbly and punches out fourth gear wheelies with a 39 tooth rear, 15 front, on a 416cc motor with stock cam.

Once it was jetted it needs no adjustment apart from a seasonal tweak of the fuel screw.

Do you have jetting specs? A local performance shop really dislikes Mikuni carbs. They highly prefer working with Kehein carbs.