Bigger carb for the WR?


2 replies to this topic
  • Matty05

Posted December 26, 2005 - 03:56 PM

#1

Has anyone tried a bigger carb on their bike? I'm interested in getting my carb bored out or keyed. Not sure but seems bigger = more top end.

Just wondering as the new CRF250's got a 40mm carb, the Yamaha 450's only got 39mm on them. The other brand MX 450's have got 40 or 41mm carbs.

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  • TeamScream

Posted December 26, 2005 - 04:13 PM

#2

Ron Hamp does a carb bore thing.
I am not 100% certain but I think the reason the Yami's have a slightly smaller carb is due to the fact that the intake tract is wider than a CRF or the others (3 intake valves).
Smaller carb bore = increased velocity, which may help in getting the intake charge into 3 seperate intake tracts efficiently at high rpms's.
If you bore the carb it may help with over rev but you may sacrifice bottom end grunt.
This is purely speculation on my part, I do not "know" the reason Yamaha uses a smaller bore carb but I know enough about engines to speculate.
Scream

  • tmckeown

Posted December 27, 2005 - 12:17 AM

#3

Has anyone tried a bigger carb on their bike? I'm interested in getting my carb bored out or keyed. Not sure but seems bigger = more top end.

Just wondering as the new CRF250's got a 40mm carb, the Yamaha 450's only got 39mm on them. The other brand MX 450's have got 40 or 41mm carbs.


Prolems is that carbs are desingned for certain amount of intake air. You won't get any more top-end if you dont increase amount of air the carburator is going to get. Only thing what you will get is lack of power on lower-end.

Best result you will get by jet tuning your bike in dyno. Every bike is different and mods work bit different too.

Timo Mc




 
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