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Discussion Starter #1
When swaping out the ok vacum syle carb that comes stock on the trx to an 39mm FCR buy a 400ex airbox and filter it bolts right up, with no modifications what so ever. But don't use any gas when starting this beast, that FCR carb will shoot fuel a foot!!!!! Perform this mod and the trx really comes to live, at least it did with my Tom Carlson motor (TC RACING) and pipe. The 450 Beats the pants off my old 426 EX which was set up with ZPS and a laeger/RPM settup. I just finished setting up the bike for nationals and can't wait for it's first ride at Birch Creek VA Next weekend! Anyway here is a list of what i have done to mine. JB A-Arms
JB Swingarm
JB anti vibe Stem
Douglas Beadlocks
Maxxis Razr MX
Ragena chain
Sunstar Sprockets
Quad Tech Hood
Full TC motor
Full TC Exhaust
Oversize bars
works connection lever with hot start
powermadd handguards
duncan bumper
pep steering stabalizer
pep ZPS shocks
39mm FCR Carb matted to a 400ex airbox with K&N
Gibson nerfs
LSR Axle
no rad. fan............................................ Just like to give a shout out all my sponsors for making this happen, Nac's Racing, Braking USA, Hinson racing, Hardcore Custom, Trackside Grafx., Outerwears, Pro Fab ATV, RPM, Iron Pony, Alpinestars, and PEP for all thier support throught this season.
 

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Sounds like a really nice set up. Good luck in VA

:D
 

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Discussion Starter #3
Ya ya I know Don't worry i'll get pics after next weekend
 

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When swaping out the ok vacum syle carb that comes stock on the trx to an 39mm FCR buy a 400ex airbox and filter it bolts right up, with no modifications what so ever.[/b]
What modifications would you need to do to the stock airbox? And how does the ex airbox fit in the place of the 450r airbox? Why did you choose the 39mm carb over the 40 or 41mm fcr carbs?
Joe
 

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Discussion Starter #5
Not sure what mods need to be done to the stock airbox try baldwin or tc www. baldwinmotorsports or www.tcracingengines.com the 450 and 400ex subframes are the same with and the 400 box just drops right in and seals up perfectly, they did not engineer it that way, it's just a quincidence. we chose the 39mm bc we can't bore the motor atva rules state 450 is the largest displacement allowed so we just bumped up the compression. the 39mm carb allowes reliability, the bike is easier to start and is less likley so flood and is prone to less kick back. you over carb the bike with the 41mm with the std bore, the 40 is pushin it. but the main reason we went with FCR is because of the accelerator pump. u hit the throttle and you're there! the throttle response is greatly improved.
 

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How is the top end with the 39mm carb in comparison to the 42mm carb. Is there any loss or gain? I understand that with a smaller bore carb, the throttle response and bottom end would be better, but I worry about the top end.
 

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Originally posted by joe1l@Mar 25 2004, 05:40 PM
How is the top end with the 39mm carb in comparison to the 42mm carb.  Is there any loss or gain?  I understand that with a smaller bore carb, the throttle response and bottom end would be better, but I worry about the top end.
how often do you need your top end....I never reach it when Im racing on trails or track....maybe in a drag race..but that not what he is doing.
 

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Originally posted by TRX450rlude+Mar 25 2004, 05:55 PM-->
<!--QuoteBegin-joe1l
@Mar 25 2004, 05:40 PM
How is the top end with the 39mm carb in comparison to the 42mm carb.  Is there any loss or gain?  I understand that with a smaller bore carb, the throttle response and bottom end would be better, but I worry about the top end.
how often do you need your top end....I never reach it when Im racing on trails or track....maybe in a drag race..but that not what he is doing. [/b]
i guess it all depends on your style of riding. I know i always short shift and i rarely ever hit my topend, except when drag racing one of my buddies or road riding.
 

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Originally posted by Jonesy+Mar 25 2004, 06:07 PM-->
Originally posted by [email protected] 25 2004, 05:55 PM
<!--QuoteBegin-joe1l
@Mar 25 2004, 05:40 PM
How is the top end with the 39mm carb in comparison to the 42mm carb.  Is there any loss or gain?  I understand that with a smaller bore carb, the throttle response and bottom end would be better, but I worry about the top end.

how often do you need your top end....I never reach it when Im racing on trails or track....maybe in a drag race..but that not what he is doing.
i guess it all depends on your style of riding. I know i always short shift and i rarely ever hit my topend, except when drag racing one of my buddies or road riding. [/b]
exactly my point.
 

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Discussion Starter #10
Exactly it's all in your riding. The majority of riders out there short shift a little. Top end yes it would hurt but just a little. If i was building the bike for dunes and drag i would of put the larger carb on it and gone with a pipe that delivers more top end. but for motocross it's all about torque and response. that's the reason i went with the 39
 

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Originally posted by nacsmx450r@Mar 25 2004, 06:27 PM
Exactly it's all in your riding.  The majority of riders out there short shift a little.  Top end yes it would hurt but just a little. If i was building the bike for dunes and drag i would of put the larger carb on it and gone with a pipe that delivers more top end. but for motocross it's all about torque and response.  that's the reason i went with the 39
sounds to me you did it right....speacially for your type of riding....I never need my top end...unless Im drag racing..
 

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on the tracks i ride, i am usaully in 2nd or 3rd and they both generally get wound out. some table tops i hit im pinned in 3rd. but then again it your style of riding i guess!
 

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Originally posted by Schmitthead@Mar 26 2004, 12:26 AM
on the tracks i ride, i am usaully in 2nd or 3rd and they both generally get wound out. some table tops i hit im pinned in 3rd. but then again it your style of riding i guess!
Tom, dont be mad 'cause my bike has the carb yours should have

and I dont appreciate you adding to my signature either!
 

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Originally posted by Schmitthead@Mar 25 2004, 07:26 PM
on the tracks i ride, i am usaully in 2nd or 3rd and they both generally get wound out. some table tops i hit im pinned in 3rd. but then again it your style of riding i guess!
:D Pinned in third....Awsome..thats what I like to hear. :D
 

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The only reason i ask is, because since i have rejetted added the intake and re-geared(13/39) my bike, i have plenty of low end and my throttle response feels good. I don't think I would necessarily need to add down low. From what I hear speaking if I went from the 42 stock butterfly carb to the 40mm FCR carb, my throttle response will still get better, and my top will still improve.

nacsmx450r what is your feel on that? my only concern is what I read about kickbacks. I definately would like to do without kickbacks!!! I already couldn't walk for 3 months because of my 350R big bore, and I never want it to happen again. Will the stock carb be a better choice to avoid kickbacks or do the fcr's work better? Also what gearing are you running for MX?
Joe
 

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Originally posted by joe1l@Mar 25 2004, 11:07 PM
The only reason i ask is, because since i have rejetted added the intake and re-geared(13/39) my bike, i have plenty of low end and my throttle response feels good.  I don't think I would necessarily need to add down low.  From what I hear speaking if I went from the 42 stock butterfly carb to the 40mm FCR carb, my throttle response will still get better, and my top will still improve.   

nacsmx450r what is your feel on that?  my only concern is what I read about kickbacks.  I definately would like to do without kickbacks!!!  I already couldn't walk for 3 months because of my 350R big bore, and I never want it to happen again.  Will the stock carb be a better choice to avoid kickbacks or do the fcr's work better?  Also what gearing are you running for MX?
Joe
well if you dont need anymore low end then you have a very good point.
 

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What I'm trying to figure out is, if the fcr carb will be worth the $400. Will there be any HP increases or is it a mere seat of the pants difference.
 

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Discussion Starter #19
It's both i forget the exact hp differences but it's a huge seat of the pants difference. I'm pretty sure i am running a 13/39 gearing but not 100% sure, I'm up at school and unfortnetly the bike is not with me. Personally i feel that the fcr is easier to start, expecially when the bike is hot, i rarley neeed to use the hot start lever.
 

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Discussion Starter #20
allright i found an ok picture of the bike go to www.offroadhaven.com click on pics. click on macon gnc race click on page 7 it's the first picture on upper left hand corner.
 
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