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Fcr39mm Taper Bored To 41mm


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#41 sredrum

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Posted 23 March 2006 - 04:49 PM

hey there...so you feel like trying to bore out a sudco mx 41mm carb>? rumor has it that 43.5 mms is attainable....id be happy with 43 or 43.5....and you appear to know how to run your equipment :clap:

i dont wanna buy a lectron...i think my carb being bored a little more would be tits!

let me know...im not in a huge hurry...just hoping to do it before i go back home to my local dunes

jason

<{POST_SNAPBACK}>


Hey JJONES660,I'll get back with you on this.I think a guy is sending me his(fcr41)to check out.I have never seen a real one yet so I have no idea how much it can be bored.I have seen pictures though and from what I seen it can't be bored that much.I have a question for you.Is the flange on your 41 that pushes into the rubber intake tube the same OD as the stock fcr39? :017: I understand the ID has to be trimmed to match the bore of the carb.

#42 JJONES660

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Posted 23 March 2006 - 09:00 PM

Hey JJONES660,I'll get back with you on this.I think a guy is sending me his(fcr41)to check out.I have never seen a real one yet so I have no idea how much it can be bored.I have seen pictures though and from what I seen it can't be bored that much.I have a question for you.Is the flange on your 41 that pushes into the rubber intake tube the same OD as the stock fcr39? :017: I understand the ID has to be trimmed to match the bore of the carb.

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yeah as far as i remember the 41mx fits the same flange as the 39....but i never smoothed mine out....

looks like i got some free horsepower waiting inside :clap:

#43 tuklugs

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Posted 23 March 2006 - 10:11 PM

there are guys that are running 43-44mm fcr. maybe it mite be a taper.

it has a 208 web cam a fcr with a 44mm throat 13.5-1 compresion.
Quote from RHC.

Edited by tuklugs, 23 March 2006 - 10:20 PM.


#44 sredrum

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Posted 24 March 2006 - 04:24 PM

there are guys that are running 43-44mm fcr. maybe it mite be a taper.

it has a 208 web cam a fcr with a 44mm throat 13.5-1 compresion.
Quote from RHC.

<{POST_SNAPBACK}>



Who is RHC?If the fcr41 can be bored to 44 I will do it but I'm sure it can't be bored that much.I don't have my carb right now or I would measure it.But if the outlet mounting flange is the same on both the 39 and the 41 I'm sure the flange would be completely machined off if it was bored that much.The limiting factor on boring these carbs out is the center section that fits between the slide.Bottom line they can only be machined out so much before there is nothing remaining.Hope I get that fcr41 soon to find out.

#45 tersejr

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Posted 24 March 2006 - 08:30 PM

RHC

Ron Hamp Cycle.... honda guys.

#46 flipp718

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Posted 24 March 2006 - 09:08 PM

I will not be posting any Dyno graphs but will explain any and all of the runs and comparisons we did between the stock 39FCR, the MX41FCR and the bored out carb from spedrum...I may not answer all your questions but were mainly trying to get my setup worked out. Other people may be worried about other things a carb will do but mine was peak HP, good tourqe #'s, throttle response, look of the curve and when and where the power hits

Bike we tested=Stock Bore, 12:1 Gyt-r piston,ported head,stock valves,ultimate 2 gas and n-motion exhaust
to get to the point the carb gained 1-2 HP all the way across the board up to 10,000 RPM and pulled 32Lbz of tourque all the way from 5,000RPM to 10,000 rpm so no need to test against the 39, already making more power.

The best and most important part to me is we tried and tried to get the MX 41FCR to pull a sweet A/F mix on the dyno and justify the high pricetag. But the A/F mix was beyond too rich at the bottom and dangeriously Lean up top...We did diffrent runs, diffrent jetting specs, diffrent pipes and they all read the same.....We did notice that the 41FCR deff. gave you gains across the board from top to bottom.

So we thru on spedrums carb (Great work by the way) and it gave me the best dyno reading of the night for sure and was the last runs we did. It gained and gained from HP and Tourqe and made one sweet A/F graph and cured the low end bog the 41MX FCR is famous for and to me the throttle response is 10x better.
This is the beat investment you can make with a minimal amount of funds, works like a 41FCR and even better......Please PM me with any questions you have and you guys better get in line because this works for sure....Sorry if i missed anything so just PM me if i forgot something....

<{POST_SNAPBACK}>

Hey
Thanks for the good write up on sredrums work I have heard alot about him and wanted to have this mod done but I was a little hesitant because I heard that once this mod is done it is hard to bet the quad to idle properly is this true? I just got my motor back with the WR crank, H/C piston,head ported, oil mod, YZ clutch pak, NMotion exhaust, and FCI intake. Will this mod benefit and work with this set- up and what jetting should be used, I live in Florida and it's always 80-90 degrees here. Right now I'm running a55 pilot, and 175 main, and 2 1/2 turns on the air screw. Please help me on this

#47 sredrum

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Posted 02 April 2006 - 05:45 PM

Some new info guys.As some of you know I just got my ported head back from Kenz.I also helped a friend pull his top end off this weekend.So I measured both heads.Mine is a 05 and his is an 04.Same thing though.The Kenz intake opening was 1.650 to 1.7 inch in diameter.It's not a perfect circle but not bad either.The stock head opening is 1.595 in diameter.So here are some numbers on what the taper bored carbs come out to at the very edge where it goes in the rubber boot (outlet side)

41mm cut at a 1 degree angle=1.650inch

41.5mm cut at a 1 degree angle=1.670inch

41.5mm cut at a 1.5 degree angle=1.686inch

Remember the center of the carb is 41mm/41.5mm but it tapers out in size so you must account for that.Your head opening needs to be atleast as big or bigger in diameter to get the best results from a taper bored carb.That also goes for a factory fcr41.I'm going to run a 41mm carb cut at 1 degree myself.That is what I have been doing so far.Bigger is not always better so if you want me to bore your carb out don't just get the biggest you can get.Make sure it matches up to or is smaller than your head opening.I wanted to offer more to you guys so the above is what you can get.I can also offer a 40mm for stock heads.Thats what I'm doing for my friend that I helped out with his top end.Here are some prices

115.00 shipped back 41.5mm/1.5 degree angle carb gets polished

115.00 shipped back 41.5mm/1 degree angle carb gets polished

115.00 shipped back 41mm/1 degree angle carb with polishing airbell side

90.00 shipped back 41mm/1 degree angle carb no polishing

115.00 shipped back 40mm/1 degree angle carb with polishing airbell side

90.00 shipped back 40mm/1 degree angle carb no polishing

Pictures :D

Posted Image
Stock

Posted Image
Stock

Posted Image
41mm

Posted Image
41.5mm

Posted Image
41mm/1 degree

Posted Image
41.5mm/1.5 degree The opening on your head will need alot of porting to use this carb so don't get it just because it's the biggest!

Later

Chris Everett

#48 homdaddy

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Posted 02 April 2006 - 06:21 PM

one of those pics looks like mine :clap: looks like your getting busy
im glad i had mine done when i did

#49 tersejr

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Posted 02 April 2006 - 06:39 PM

:clap:

Awesome. More options :clap:

#50 BB3

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Posted 02 April 2006 - 06:57 PM

Man that last picture look's like someone's carb i know hehe.
Good job chris :clap: :clap:

#51 puddle jumper

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Posted 03 April 2006 - 02:33 PM

haha,looking good :bzr:

#52 panteramatt

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Posted 03 April 2006 - 06:29 PM

So would it be ok to get the 41 with a stock head if your planning on getting it ported later? Do you loose anything with that setup compared to stock?

#53 tersejr

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Posted 03 April 2006 - 07:18 PM

I will be testing out that very question :011: Well, a little bit different, but all info and facts are still great to have.

Yes, dynos will be involved. :bzr:

Edited by tersejr, 03 April 2006 - 07:19 PM.


#54 tersejr

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Posted 12 April 2006 - 02:43 PM

I dynoed today and all I can say for now is expect to jet really far up (rich) from the your current jetting with a bigger carb on a unported head.

Graphs will be up later.

Before the 41.5mm @ 1* taper..... 52.7HP


After the 41.5mm @ 1* taper...... :rolleyes:

#55 panteramatt

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Posted 12 April 2006 - 04:08 PM

So what did it do?

#56 tersejr

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Posted 12 April 2006 - 05:37 PM

Mods in sig with stock carb 160/NCVQ2nd clip/ 45 2 out @ 5000ft & 50*

Same mods in sig but now with the bored out stock carb to 41.5mm w/ 1* taper and my hack job to port match the intake boot... 182/NCVQ 5th clip/ 45 1 out @ 5000ft & 73*

#57 panteramatt

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Posted 12 April 2006 - 06:34 PM

you never posted your hp after the 41mm. :bzr:

#58 tersejr

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Posted 12 April 2006 - 06:44 PM

With the stock carb I had 52.7HP

without re jetting the 41.5mm I had a NASTY curve and peak HP was 46.8 :blink:

After rejetting ^^^^^^
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..........54.4HP & and after airing up the tires to 14psi from the 5psi that was in them....
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.....56.4HP :P

Edited by tersejr, 12 April 2006 - 06:45 PM.


#59 schwendi

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Posted 12 April 2006 - 10:05 PM

nice results

what was your jetting before and after?

thanks

#60 tersejr

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Posted 12 April 2006 - 10:17 PM

Post #56 is before and after.

Wait till I load up the graph that show what the 41.5mm looked like before I rejetted it :blink:

Here ya go, both runs are with the 41.5mm 1*

The bad looking one is with the same jetting I had (160/ ncvq 2nd/ 45 2out) when I had 52.7HP. Big change.

The red line is after a long jetting session. Ended up with a 182/ncvq 5th/ 45 1 out @ 5000ft & 73*

Posted Image

Edited by tersejr, 12 April 2006 - 11:02 PM.





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