43 mm FCR Carb Boring---

[hendershot106]

Can somebody help me out here----- what exact area of the carb are they talking about boring---- i have only two things left i want to do to my motor and this is one of them-- but there is no way i am waiting on sending my carb to and from sparks for this---

[patrickj75]

call chad beattie at DRG. his number is 301-910-9850. he has good prices and great results on the dyno. he's doing an 07 crf carb for me right now.

patrick

[chad502ex]

Originally posted by patrickj75
call chad beattie at DRG. his number is 301-910-9850. he has good prices and great results on the dyno. he's doing an 07 crf carb for me right now.

patrick

thanks for the plug.:)

[hendershot106]

how bout an explanation of what this really consists of please chad????????

[chad502ex]

Originally posted by hendershot106
how bout an explanation of what this really consists of please chad????????

boring a carb can be done two ways,... (1) straight boring (2) taper boring

I prefer to taper bore because a taper will increase velocity of the airflow through the venturi of the carb and increase the pressure differential across it. There are other builders whom prefer a straight bore. My feeling is that straight boring a FCR reduces the throttle response "feel" of the carb

The specific taper must be determined as to not move the "image" orfice to far forward away from the carbs venturi. I have found a precise taper angle that has been independently dyno tested to provide about 3hp increase.

Increasing from 41mm to 43mm is roughly a 10% increase in cross-sectional. If velocity of the airflow is maintained after boring, the 10% increase in cross-sectional will reflect a 10% increase in cfm.

carb airflow measurements before and after modification can be validate on flowbenches at standard depressions.

The boring process involves disassembly of the entire carb down to the throttle body. The OEM venturi ring is removed and a new venturi ring is installed. The venturi ring is a ring in the center of the FCR carb that the slide itself slides over and the needle penetrates through its center. Without replacing the center ring with a new 43mm billet ring, 43mm or bigger can not be obtained. After the throttle body has been taper bored so that its center is measured to 43mm, the outside endpoint of the taper within the input bellmouth is blended for smooth transitioning of the "velocity stack" of the carbs Noss adapter. A Noss Adapter is also bored together with the FCR throttle body as one piece. A NOSS adapter is required to adapt the FCR to the 2004/05 TRX450R intake boot. I am not permited to get into pricing details though, but generally the overall cost of the boring process with parts and labor is about the same cost as running 100 gallons of regular pump gas through it,... hehe

[hendershot106]

Originally posted by chad502ex

A NOSS adapter is required to adapt the FCR to the 2004/05 TRX450R intake boot. I am not permited to get into pricing details though, but generally the overall cost of the boring process with parts and labor is about the same cost as running 100 gallons of regular pump gas through it,... hehe


ur pretty clever------ whats the return time on this process chad???? --- and i have a 2006 er carb-- not the long boot such as the 04 05-- it has the shorter adapter

[hendershot106]

ill just call u.

[chad502ex]

heres a pic.

[chad502ex]

hey patrick, since you didn't ship me your intake boot, please be sure to match the intake boot to the carb flange opening.... make sure the transitioning is smooth so no turbulance develops between the carb and the port. I normally match the boot to the carb and port when possible.

Enjoy.