Bored carburetor

[brewster426]

So what's the big hype with boring the stock fcr carbs? And how exactly are they done? Is it a tapered bore or just straight through? Any help would be appreciated. I might just have to get my hands on one done by dasa to compare. Thanks.

[Atvers]

May I ask what are you trying to aim in getting a bored carb? In my idea it is better to get a aftermarket carb than to bore out your oem carb.

[brewster426]

I have buddies that have had them done by dasa and say is a night and day difference. I just want to know more info on it. I can get my hands on one and match it. That's prob what ill end up doing.

[2001400exrida]

If you have the mods to compliment a bored carb there are definitely benefits. I will agree there is tons of hype over this and many people get it done and probably don't see the results that they are going for. I know in TT and FT racing, bored carbs are somewhat popular however i know several A class and pro am riders that run bone stock 04/05 carbs on their built 450's and still take the podiums.

I run a crf FCR carb on my trx and while i did not notice an immediate difference, i can tell that the throttle hit is harder, whether or not i'm actually getting more power from the carb, i'll never know. After i get the head work this winter and up my compression i plan on having the carb bored, at that point i'm hoping to be able to feel some difference. Certainly there's power to be had from a bored carb, but you do need the added modifications with the motor and head to really benefit. Slapping a bored carb on a stock motor won't show much gain.

[brewster426]

Well I have a 08 I'm building with a 02 Crf head that has had a mild port job on it with a Crf cam, 13.5:1 piston with a Crf head gasket. I think a bored carb will be somewhat beneficial. Just didnt know exactly what they are doing and calling it bored.

[chronicsmoke]

Well I have a 08 I'm building with a 02 Crf head that has had a mild port job on it with a Crf cam, 13.5:1 piston with a Crf head gasket. I think a bored carb will be somewhat beneficial. Just didnt know exactly what they are doing and calling it bored.

They bore out the body of the carb.. Taper bored is supposed to be better for invreased air velocity. I got mine straight bored by Matt @ Dynomite in AZ for $125

You may loose a bit of bottom but you'll gain it on top..

I got a CRF250 dirtbike carb that was 37mm and had it bored to 42.5
(37mm and my 42.5 above it)
http://imageshack.us/a/img839/5768/img2662nt.jpg

[2001400exrida]

don't they add a venturi ring on some of them too chronic?

[chronicsmoke]

yes - to adapt it on the 04/05 airboot I believe.. I didn't go that route so I don't have experience with it..

I have a 2006 airbox/boot/big filter on my 05 (cost me 60 bucks for everything, would have been 50$ just for the ring) It bolts up great and gives you the advantage of using the big filter..

[beastlywarrior]

May I ask what are you trying to aim in getting a bored carb? In my idea it is better to get a aftermarket carb than to bore out your oem carb.

Lol dude there isn't any better carb out there than an fcr

[81dasher81]

agreed, go with fcr. basically the only time you taper bore a carb is if you want to tame it down some, like if the throttle hits too hard. the fcr doesn't increase your horsepower, it just gives you better throttle response. i agree, the bored fcr carb will help you out quite a bit.

[brewster426]

I'm getting a dasa carb from my buddy. These things sure are extremely expensive to rebuild. I'm 1500$ invested already just in parts. But I did buy all the Crf head stuff. Hoping to make it to Texas next month for the Caleb Moore benefit. Haven't rode in 5 months, so I guess I'm gonna goon it up in the c class.

[2001400exrida]

No doubt these motors gets expensive, if you look around and do your research though you can get great power and avoid the high dollar builders. I know guys that race and have 5k in their motors because they want to run the best names. Talk to some other racers that have less than half that and still put down great power.

I'm almost $1,000 into with my motor build and that's $250 for head port and valve seats cut, $130 for new valves and springs, $150 for piston, $150 for carb bore, not to mention the HMF pipe and s2 cam that is on there already. I'm also paying $160 to have my stock swinger cut down 1 inch.

Venom is doing my port work, the guy has been building motors for racers for years and he knows his stuff and is not afraid to share information, he also has good prices. Sredrum is boring the carb, he's as good as any and with reasonable pricing.

hoping to get 55hp on a SB, SS motor.

[Lquad71]

don't they add a venturi ring on some of them too chronic?
If it is over a certain size bore then a billet venturi ring will be replaced, im not sure why, it may be because of the material it is made of and they dont want to machine that or it may be easier to make their own ring or maybe the stock venturi ring is too small depending on the size of the bore. The adaptor that chronic is talking about is mounted on the ouside intake of the carb to an 06+ intake boot, while the venturi ring is the little ring in the middle of the carb that the slide will cover up when the throttle is closed.

[2001400exrida]

For the FCR to fit on my 05 I had to purchase a Noss adapter that gets epoxied on and machined along with the carb intake. Essentially all the noss adapter does is legnthens the carb a bit so that the stock intake boot will reach it. Can't wait to get my 42.5mm back from sredrum!