Ride Report: FRP Carb modification

[john_bilbrey]

I've had a couple chances to ride since I got the FRP carb modification done to my '03 220. Here's the info:

Bike: '03 220
Mods: no airbox lid, jetting, Gnarly Desert/PC2, Race Tech suspenders up front, Wiseco piston, 13/50 gearing

What a difference the carb bore makes! It made as big(if not bigger) of a difference than the Gnarly Desert pipe/jetting combo. This thing absolutely rips now. No loss on the bottom, bunches more in the meat of the powerband and up top. It really pulls hard now all through the rev range. Jetting was spot-on when I got it back from FRP (45 pilot, 160 main, stock? needle in the middle clip).

If you are looking for more beans out of your ride, this is the way to go. Cheap too! (About 1/3 the price of a pipe/silencer combo)

 

[lepper]

Wow.... that's a fat main!

I have the RB carb mod on my 200, 36mm bore/ divider plate and running a CEK with a 150/42...

 

[m0rie]

With the stock needle on a 220 and a 36mm carb that doesn't sound too out of line on the main actually. The B taper needles (which the stock needle is) are going to take a larger main then a C or D taper needle.

 

[Green Hornet]

Are you sure its a 160 not a 150????

 

[adam728]

Are you sure its a 160 not a 150????

Fredette sent mine back with a 160 main. I run a 155 now, but am also ported, which can change jetting requirements.

Larger carb = less air velocity = larger jets required

 

[lepper]

RB is a tad different on that part... more velocity.

 

[1swarty]

FRP Carb Mod

I have FRP carb mod, head mod, rad valve, fmf and ported cylinder. I don't even know what jets are in the carb, Jeff sent it to me 4 winters ago and said it would work and it does!
Replaced Wiseco piston and rad valve reeds at end of last season. I put a new pipe on it as I beat the old one up pretty good The thing runs great everywhere and the only downside is it made it a bit of a gas hog. 97KDX220

Swarty

 

[lepper]

Porting is the main cause of that I think. I have heard of too many horror stories after porting that I think I will stay away from it.
I just got my head modded by RBD and can't wait to try that out in the spring. Should make for some more bottom end and snap.

 

[Zerotact]

One thing people seem to forget about the RB cab mod is while it is bored out to the same 36mm, they install a plate that goes right through the center. So, while bolth mods work great, the straight carb bore without the divider plate installed, has a tad bigger hole than with a divider plate. It may be minor, that diver plate takes up some space....

I'd be interested in an actual comparason on a flow bench to see what each carb flows. Basic physics would tell us that a 36mm hole with a thin plate through the center would have slightly less surface area, than a 36mm hole with no plate.

 

[lepper]

I think the main difference between RB and Fredette's mod is, that Fredettes will only benefit the 220 since it has a 33mm carb if it is only a carb bore. Where RB's is the divider plate, slide shave to a leaner # 7 cut and a few other goodies he does to the carb body to give it better flow. Plus RB sends his modded carb with a CEK needle or a DEK upon request.

I really have no real working knowledge of Fredettes carb mod but just what I have heard. The RB on the otherhand though......

 

[john_bilbrey]

Pretty sure on the 160 main, although I don't want to tear into it to check.

 

[Sunny State KDX]

how much does Fredette get for his carb mod??

 

[john_bilbrey]

It's around $100 including shipping both ways (about $70 just for the work though).

 

[adam728]

I have FRP carb mod, head mod, rad valve, fmf and ported cylinder. I don't even know what jets are in the carb, Jeff sent it to me 4 winters ago and said it would work and it does!
Replaced Wiseco piston and rad valve reeds at end of last season. I put a new pipe on it as I beat the old one up pretty good The thing runs great everywhere and the only downside is it made it a bit of a gas hog. 97KDX220

Swarty

You are probably running pretty rich with his jets. Mine was pig rich. It was much faster than stock, but I gained a lot of power when I jetted it after break in. I have the same mods as you, but minus the RAD. I've seen over 60 miles on the trail without touching reserve (riding HARD in deep sand), and can get 85+ miles on the road from a tank. I can run a 3 hour harescramble without adding a drop. If you have spooge too then you are definitly rich.

 

[1swarty]

FRP Carb

I really have no spooge and I did do a plug check upon initial set up. I could go around 64 ground enduro miles before reserve, prior to mods. I did it all at one time so I am clueless as to the progression or what effected what. My cylinder had the port timing dialed in by FRP and I finished it myself. I now hit reserve around 56 ground miles. I am a Super SR, so I only race HS 2hrs, I have never run out but I did go on reserve close to the finish and lost a place in the process. In my experience the road sections of an enduro burn far more fuel than the actual trail.The time you spend on the main is more of a factor, riding style is also a big contributor.

Swarty

 

[soldsoul4foos]

ok. i know this is a stupid question. what/who is RB? I do know what FRP is though :) Thanks.

 

[lepper]

www.rb-designs.com

 

[Sunny State KDX]

hmmmmmm $100.00 bux you say?? thats a good bit cheaper than the RB mod.

 

[adam728]

I really have no spooge and I did do a plug check upon initial set up. I could go around 64 ground enduro miles before reserve, prior to mods. I did it all at one time so I am clueless as to the progression or what effected what. My cylinder had the port timing dialed in by FRP and I finished it myself. I now hit reserve around 56 ground miles. I am a Super SR, so I only race HS 2hrs, I have never run out but I did go on reserve close to the finish and lost a place in the process. In my experience the road sections of an enduro burn far more fuel than the actual trail.The time you spend on the main is more of a factor, riding style is also a big contributor.

Swarty

I see now.
The few harescrambles I have raced have been REALLY tight, no road sections, maybe just a motocross section or a few wider straights. Lots of 1st and 2nd gear stuff. When you said gas hog I was thinking you meant you were running out at like 30 miles or something.


Sunny State,
If I remember right it was $60 to bore the carb, $13 for jets, and then whatever shipping ran. I had all my stuff done at once, so Fredette shipped everything together (cylinder, pipe, silencer, head, carb, fender). Still, shipping was only ~$25 from him.

 

[canyncarvr]

re: '..thats a good bit cheaper than the RB mod'

One is an apple.

...the other is an orange.

 

[lepper]

Ain't that the truth!

 

[soldsoul4foos]

how about an english interpretation of the apples and oranges comment :)

 

[lepper]

Let's reflect...

FRP... Bore Carburetor and Install new Jets (220's only) $83.00



RBD... (220 or 200) $165.00 includes return shipping

Boring carb to 36 mm (gives you a better top end)

Installing divider plate (gives that low end response, like a smaller carb)

Modify slide
Install new needle (gives the carb that personality)

Change jets (if necessary)

Modify jet block (helps with the over all performance)

Modify low speed circuitry This part of the modification along with the other mods really brings the air mixture screw into play. With only very small adjustments, you can keep your bike running at its peak as you change altitude or with weather changes during your ride.

 

[lepper]

I just want to say... both know their stuff!

Just depends on what you want, they are definately different animals and the pricing reflects that.

An alternate to the 220 Fredette carb boring is buying a used 35mm PWK from a KDX off of that on place. :clue:

All 35mm PWK's are not the same.....

 

[soldsoul4foos]

that was a great description. thank you.