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I use a duel valve spring kit from walsh, Witch i believe is just a kibblewhite kit.
They use PSI springs. (as of last year anyway)

As far as the $300 goes, totally brain farted on the valve springs. But, that is not req'd, but suggested!

Rowe...if you need any more help, you can PM any of us. Walsh YFZ helped me out a ton when I was doing my swap. I did have the quirky ON then OFF then ON to start issue when I was e-start, but a TOS elim from KMS solved that issue for me. I gutted my harness myself to save some money...but all other prices listed above are about spot on. My set up all-in-all was about $550 with the valve springs. I would NEVER go back...this set up is much cleaner, and the quad is much more responsive, hands down! I am also running close build to yours and Blue Ranger's...14:1, P&P, ATP int cam, 08 exh cam.

You will love it...start saving :)
u forgot to mention that you can sell your old fi parts to make up some of the money and help save.
 

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Discussion Starter #24
Definitly true on selling the FI parts. I.had my throttle body bored to45mm would the 43.5 be bored large enough For my build? I also plan on going bigger later on and wouldn't wanna have to go to a larger carb later on.
 

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Im running the stock FCR 41 on my build

ATP 14:1 piston
ATP intake cam
'08 exh cam
+2 Exh valves
P&P

With no issues. Do I plan on boring my carb to 43.5, yes....maybe nxt year though. The power I have is way more than sufficient. I don't know what build you plan on going with, but talk to Williams or Walsh if you have any doubts.
 

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My opinion (and everyone has one) comes from the years of R&D we did on the Raptor motors. If you're building an over bore drag bike and using cams with over 0.400" lift and 260 degrees duration @ 0.050" you can gain top end with the bigger carburetor. But if you're riding and racing MX style under 500cc and MX type cam profiles then the 41mm FCR will work well. I can find other places to invest time and money which will make the bike come out of turns faster and accelerate i.e. lighter wheels, tires, chains and sprockets or mill the deck and set the quench at 0.040" or increase compression, or modify your rear brakes to produce zero drag. (others will disagree but that's just my opinion) good luck.
 

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Definitly true on selling the FI parts. I.had my throttle body bored to45mm would the 43.5 be bored large enough For my build? I also plan on going bigger later on and wouldn't wanna have to go to a larger carb later on.
what build and type of riding will help. im going bigger on mine bc i dune/hill shoot and dont care much about losing a bit on the low end of rpm band.
 

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Discussion Starter #29
Well I've a fairly good build right now. Mine is a strict duner/ hill shooter so I definitly think my main focus is in the higher RPMs.
 

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get a yfz fcr carb if you want to go big, from talking to trx/yfz groups, the yfz fcr casting has more material and can be bored to 44mm w/o adding a billet venturi.
 

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It is difficult to find a dyno run where the only variable was carb vs injector. Comparing the blue line, injector to the green line, carb in this dyno chart also includes the +2 exhaust valves with the carb; not a fair comparison. Regardless of the fact that we have very little data to suggest or influence the switch to carburetor you can simply use this as your metric. Ask Walsh racing if they plan on switching either of Cody Gibson's LTR motors back to injector or ask anyone on this site who races an LTR with a carb if they ever consider going back and there you will find your answer.
 

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Anyone running a different ecu with carb set up?

I have an 06 carbed, would I gain any benefits running an 08 ecu or a procom ecu?
 

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from reading and watching videos on the 08 ltr, the ignition curved and injector pulse was changed to minimize wheel spin on take off and when coming out of a turn, which probably means that it has a less aggressive curve.

i made 61whp fi then 67 with a bad head gasket with the only thing i changed was the 45mm tb to a 46mm lectron, shorten the intake manifold and made a different intake tube set up
http://www.ltr450hq.com/forums/dyno-tuning-room/44120-carb-dyno-pulls.html
 

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Anyone running a different ecu with carb set up?

I have an 06 carbed, would I gain any benefits running an 08 ecu or a procom ecu?
The only option is to run the 4217 MSD box. I run it on my carburetor bike and love it! NO more quirky problems with the OEM wiring and CDI box. The MSD is laptop programmable but not easy to set up because the flywheel will need to have all the trigger tabs ground off and 1 60 degree tab about 10 degrees BTDC welded to the flywheel. Racer's edge AZ is great at setting up a flywheel for you. they have the MSD ignitions and the MSD coils also. I was the second LTR, and now maybe the only LTR running the MSD that I know of. I have a few different curves but the one Racers edge dyno tested for their carburetor 700 raptors seems to be a good starting point. They really helped me get the ball rolling and after testing on a 200' track I have it pretty dialed in now.
 
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