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Old 02-22-2010, 09:38 PM   #121
meat popsicle
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Quote:
Originally Posted by outfront
Can someone direct me to that thread? Ive hunted this site for a step by step, no luck. Maybe I need a step by step, using the search feature.

...
not sure if it:

http://www.advrider.com/forums/showthread.php?t=206427

has the info you need, but it can't hurt.
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Old 02-23-2010, 05:55 AM   #122
MODNROD
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Fcr 37 ......

....off a 2008 YZ250, 168 main, 42 pilot, std air jets, OBEKN needle on 4 fm top, and a home-made slip-on, with pocket-ported head and 5-angle seats to give 12:1 comp ....... === ....... power-only front rises in second, with 17/38 gearing, smooth surge of power from 2300rpm, high-12's, somewhere over 175kph top end. Wired up TPS, 2 colours are the same (on a 2006 KTM SM anyway), so easy to do, only 50Ohm difference between resistance values on FCR and BST TPS switches (negligible), haven't noticed much difference with or without TPS though to be honest.

Just thought I'd mention it for anyone who wasn't sure if it was worth it, or having difficulty trawling thru conflicting opinions for a set-up that MIGHT be a place to start. I live 300m above sea-level in a very dry (under 15% humidity) environment.
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Old 02-23-2010, 08:40 AM   #123
outfront
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Fcr

Quote:
Originally Posted by meat popsicle
not sure if it:

http://www.advrider.com/forums/showthread.php?t=206427

has the info you need, but it can't hurt.
THANKS.

After reading the pros and cons; I think I'll mod the BST and sell the FCR.

Im riding the TAT this summer and I don't want carb issues at 11k ft.
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Old 03-20-2010, 07:19 PM   #124
mstenkil
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Had to replace carb so went with FCR-MX 39mm

Hi there,

Just wanted to share my 2cents. I had to replace my 40 BST because I had the time and wanted to get some low in snap that I have on my 450 but lacked on my 03 LC4 ADV. I manged to snap off the corner off top and bottom of the lower bowl. I was tempted to just do Creepers mod and JB weld it permanently and pray I never had to mess with the jets...not likely so i went shopping.

Ended up with a lightly used 2008 EXC FSR-MX 39mm with throttle cables for $180 delivered from ebay. I then purchased JD Jetting Kit with Needle screw. Here is what I have in it for elevation set for: 1500-3000ft.
#42 pilot jet
2 turns out on the fuel screw
Red marked needle in the #5 from top clip position
#172 man jet
Thicker O-ring for the accelerator pump linkage modification as described in the kit

So far i have been lucky with the boots and its aligned pretty good. I have taken it for some small spins and it hasn't moved. I must say Creeps post saved me I have some sort of issue going on with my estart so i have to kick it. It used to take numerous kicks with the choke on. Now, its one-two kicks with the choke on for a few moments. It has significantly helped out starting it and its more responsive. Super happy right now
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Old 10-04-2010, 06:24 PM   #125
rruugger
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I had a fcr 39 carb and a leo vance pipe installed on my 07 640 adv ....man it runs much stronger! But I do have issues in the miles of endless woops we ride out here in california desert. It floods-out and dies in that type of terrain. Had it back to the shop a few times and they change the needle valve and some other adjustments, but to no avail. IS THERE A CURE FOR THIS????????????? Just ran a 1300 mile rally, bike ran flawless with this only issue. Any help from the ones that are wise in the ways of 640 carburation would be appreciated.
Or direct me to where to ask this question.
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Old 10-04-2010, 07:47 PM   #126
dirty_sanchez
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Sir-

Check the float height.

You can do a rough check with the carb still in the bike by holding the free end float bowl overflow tube (which normally hangs down by the swing arm) even with the seam where the float bowl mates to the bottom of the carb. You're making a horseshoe shape with the tube with the open end at the top.

While holding end of the tube next to the carb body but above the top of the float bowl open the drain a bit with a phillps head and make note where gas begins to drain out of the overflow line by slowly moving the end of the tube up and down. Once you slowly begin to move the end of the tube up and down while being held next to the carb, you'll notice where the gas begins to drain out of the tube. From what I understand gas should begin to drain out of the overflow tube at the seam. If the float is too high, gas will drain out of the tube above the seam, too low-below the seam.

The fuel should just begin to show right at seam level.

Dirty
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Old 10-04-2010, 08:02 PM   #127
rruugger
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Thank you will give it a try.
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Old 12-08-2010, 07:39 AM   #128
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Thumb

dellorto
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Old 03-26-2011, 08:10 AM   #129
dzrtracin
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2000' sxc 400

Here's the deal, i just bought back my sxc 400 from a buddy i sold it to 5 years ago. Back then i was going to get rid of the BST but never did. Now that its back in my possesion i plan to. I have been through all these carbs threads & have found nothing for the lc400, just the 640's. Question #1 will the TM40 be a direct fit front boot & rear boot? Cables, do they need to be changed, or use the existing one's? Basic jetting for 2500' elevation.

RIDE ON!!!!!!
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Old 04-21-2011, 11:51 AM   #130
hammmerboy
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1995 620

I have a '95 620 with the Dellorto PHM 40 carb. It needs to be rebuilt- any thoughts on this? Any words of wisdom?
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Old 04-21-2011, 08:17 PM   #131
Tseta
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Katumo's "Rebuilding a Dell'Orto PHM SD Carburator"-thread will answer most, if not all, of your questions...

-T
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Old 12-08-2012, 11:57 PM   #132
Young-Gun
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I have myself an old '98 640 LC4 with the BST and thinking on the FCR-39. Does anyone know if all FCR-39 carbs are the same or were the same models tweaked in different ways to suit other bike makes and ages?
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Old 08-12-2013, 03:43 PM   #133
losiu OP
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Back to business :)

Hey everyone,

I decided to come back to the original question after mhy long-ish absence here because I have recently purchased a used Husky TE250 with Keihin FCR37.
Also, about a month ago I rode a friend's 625SXC with an FCR41 and I got a pretty good idea how these carbs work (although there may be some who will disagee - that's totally okay with me).

So... the TE250 obviously has a much smaller engine than an LC4.
Naturally, the powrer is much higher but its delivery is very interesting. The bike is so smooth it's almost not right and as the revs go up, it starts producing more and more power until the bike literally goes flying.

When a freiend asked me to get on his 625SXC (trusting that if I was the wheelie master (haha) I would know if his bike ran right), he wanted to make sure that the power was all there because he had doubts.
I was stupid enough to believe him about the lack of power of his SXC and almost killed myself pulling the bars way too hars in 3rd gear trying if the beast would wheelie. The bike also ran smoother than my 640 with the BST and had much more power at higher revs so if you're looking for a set up that will allow you to win drag races, the FCR is the answer.

And in my view this is exactly the secret.
FCRs are made for racing and going flat out whenever possible. They provide more power for the engine from the mid - up, while the BST with the popular mods provides a way snappier throttle response at lower revs and, although the engine does't run quite as smootly as with the FCR, it seems to give it an extra portion of torque at lower revs, which I personally love.
Also, a BST carb doesn't provide as much power at the higher revs as an FCR.

Okay - I know that a CV carb is not good for serious competition riding but most of us don't compete. When I started this thread I was trying to establish whether the FCR is worth the extra money. I think that after all those years I found the answer. I love the big bore engine torque and a good open exhaust, air intake mods and a properly jettec BST provide loads of it.
The FCR is a carb is meant for racing and getting max power at the high revs in order to go quicker and achieve higher speeds faster.

Again - it's just how I understand it.
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Old 08-12-2013, 04:45 PM   #134
meat popsicle
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Very reasonable losiu,

and this will help anyone who is within reach of help; for others... we can only hope their replies are entertaining!
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Old 08-12-2013, 07:48 PM   #135
dnrobertson
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Quote:
Originally Posted by losiu View Post
Hey everyone,

And in my view this is exactly the secret.
FCRs are made for racing and going flat out whenever possible. They provide more power for the engine from the mid - up, while the BST with the popular mods provides a way snappier throttle response at lower revs and, although the engine does't run quite as smootly as with the FCR, it seems to give it an extra portion of torque at lower revs, which I personally love.
Also, a BST carb doesn't provide as much power at the higher revs as an FCR.
To me, one of the BIG advantages of the FCR over the BST is the much improved throttle response as low speeds. The accelerator pump in the FCR allows much quicker throttle response than any BST!

I agree that (with my bum of the pants testing), once the revs hit about 5000 rpm, the FCR equipped bike accelerates really well.

I don't have my FCR tuned for max power, but more for fuel economy equal with the old BST. Last trip (using FCR) best was 23 km/litre (cruising at 100 kmh) worst was 18 km/l.

A couple of years ago, I had the chance to run the BST equipped bike flat out for a long distance. Top speed for me and gear was 150km/h (GPS indicated). Recently, same road, same bike except with FCR 39. Top speed 163 km/h. I know not scientific at all.

Would I ever go from my FCR 39mm to the BST? No!!
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