06yz450 Rhc Fcr Carb Mod


9 replies to this topic
  • CROGGR

Posted June 30, 2006 - 09:08 PM

#1

In the quest for more power I have tried just about every aftermarket bolt on that there is with very disappointing results....which finally led me to try RHC's FCR carb mod bore. He bores the carb almost 5mm and does it on a different angle to get a better charge into the head. After bolting the carb on I started the bike, set the idle, and then went up the street. (Couldn't wait for the dirt) From the first crack of the throttle my smile started to curl up my cheek bone! This mod is worth way more than the price that he charges. The bike is so much more responsive and revs quicker with much more authority! I brought the bike back and called Ron and thanked him for such a great change to my bike. He gave me a few other tidbits to help the bikes power and ridability.

So I implemented them and headed for the dirt with my brothers stocker. It is set up just like mine....same tires same ect. With a GPS strapped to my helmet I did some hillclimb runs with both bikes and always backed up the results at least three times before coming to a conclusion. The RHC carb mod made a 3 to 4 mph difference on every hill. Most of these runs were made in second or third gear! I was really really impressed. A friend of mine bought a KTM525sx and put the big bore and stroker crank in it. A really cool bike. The kit cost well over $1000 and it only increased the speed of the bike by 1mph up these same hills. We tried different gearing and such, but didn't get the bang he was searching for. He will be calling RHC very soon. Any bike with a FCR carb will love this mod. And it makes the bike more ridable especially in slow conditions. The bike feels like it has a flywheel weight it carburates so much better and smoother down low and then when you hit the throttle hard it feels like you just pushed the warp speed button on the USS Enterprise!

In side by side drag races, it seems to have increased the bikes accelleration by about a bike length a gear. Very very impressive! :ride: A big Thanks goes out to RON HAMP from RHC :banana: You can contact him at www.ronhamp.com. This has been the best performance mod for the $ I have ever experienced! And I believe to be a much needed one for the YZ! :ride:

note* just noticed I posted this in the WR forum and not the YZ :ride: allthough this mod will work well on the WR could someone please move this to the YZ forum for better exposure?! Thanks!

  • flintlock28

Posted July 01, 2006 - 03:25 AM

#2

Doesn't boring the carb tend to make it better at high speed/high RPM situations, while giving worst performance at low throttle/low RPM??

I think Honda has a problem with the CRF's having too large of a carb bore (40mm) that has been hurting low RPM response.....anybody have any comments??

  • Ron Hamp

Posted July 01, 2006 - 05:08 AM

#3

honda just increased there carb size for 07 on the 450

  • ben_suhard

Posted July 01, 2006 - 06:38 AM

#4

Doesn't boring the carb tend to make it better at high speed/high RPM situations, while giving worst performance at low throttle/low RPM??

I think Honda has a problem with the CRF's having too large of a carb bore (40mm) that has been hurting low RPM response.....anybody have any comments??


Yep, a smaller carb is better down low coz the air speed is greater.

  • Matt96xr6

Posted July 01, 2006 - 06:54 AM

#5

honda just increased there carb size for 07 on the 450


but they also changed the valve size in the motor to compensate and make it run as a total package

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  • grayracer513

Posted July 01, 2006 - 07:12 AM

#6

but they also changed the valve size in the motor to compensate and make it run as a total package

Coordinating each modification with all of the components in the engine as a cohesive unit is the only way to really get anything out of something like this. Making single mods in isolation from the rest of the top end may give you some gains, but you'll get much more if you match everything that the air and fuel passes through, from the air filter to the muffler to the same purpose. Only in cases where a single component has been really inadequate to work with the total setup (which would likely be true if the engine was modded and still running a standard FCR) will reworking one thing provide a major boost.

Nevertheless, good work Ron! :ride:

  • aford541

Posted July 01, 2006 - 07:35 AM

#7

I am a RHC fan also, we had a head, cam and carb done by Ron in 04 with great results.

  • CROGGR

Posted July 01, 2006 - 10:32 AM

#8

Yep, a smaller carb is better down low coz the air speed is greater.



All things being equal that may be true however, what if the carb is too small to begin with? The Yamaha needs and responds very well to this mod! And the power off the bottom is stronger than stock! As the power climbs the pull is even stronger! To quote both of my brothers after riding my bike " I wouldn't have believed it if I hadn't ridd'in it for myself! That is truely amazing what that carb mod did to the personality of the bike! I gotta have mine done and now!"

  • Ron Hamp

Posted July 01, 2006 - 11:11 AM

#9

if the signal @ the nozzle in the carb is increased lets say by changing the shape of the air horn even though the carb is bigger there will be an increase in trottle response .also a simple change in ex valves size with out decreasing port cross section will not yeild tremendous results

  • ben_suhard

Posted July 02, 2006 - 05:01 AM

#10

All things being equal that may be true however, what if the carb is too small to begin with? The Yamaha needs and responds very well to this mod! And the power off the bottom is stronger than stock! As the power climbs the pull is even stronger! To quote both of my brothers after riding my bike " I wouldn't have believed it if I hadn't ridd'in it for myself! That is truely amazing what that carb mod did to the personality of the bike! I gotta have mine done and now!"

You could be right, I'm happy with mine as is.





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