What would be better? Exhaust mod or bigbore?
#11
04-22-2008, 03:56 AM
RE: What would be better? Exhaust mod or bigbore?
Wow, I totally disagree with you guys on the carburetor. I can't speak for the Mikuni, but I had the FCR35 from Jerry Leighton and it really transformed the nature of the power delivery. Off the throttle was a burst of power and I mean with AUTHORITY. If you dump the clutch, one of two things is going to happen - either the front end will come up, or the rear wheel will break loose, there will be no in between. 
Not to say you can't control the power - you need to feather the clutch to do that, but if you want a snappy response, a pumper is the way to go, or more specifically, you want the slide directly connected to the throttle cable and not a butterfly valve and rely on engine vacuum to slowly raise the slide like the CVK.
I noticed a big difference in this when I switched out the CVK for the FCR on my 331. Maybe the one you guys tried wasn't jetted right or something or maybe the effect is more pronounced on a 331 than on a 250 and you only tried that setup? So maybe it's not worth it to pumperize a 250, I don't know, but it was definitely worth it on the 331. I was already big-bored when I got my carb, but I did leave the CVK in for a few rides just so that I could tell what the difference was when I dropped in the FCR.
I did spend a good bit of effort fine tuning the FCR and it only got better after that.
Not to say you can't control the power - you need to feather the clutch to do that, but if you want a snappy response, a pumper is the way to go, or more specifically, you want the slide directly connected to the throttle cable and not a butterfly valve and rely on engine vacuum to slowly raise the slide like the CVK.I noticed a big difference in this when I switched out the CVK for the FCR on my 331. Maybe the one you guys tried wasn't jetted right or something or maybe the effect is more pronounced on a 331 than on a 250 and you only tried that setup? So maybe it's not worth it to pumperize a 250, I don't know, but it was definitely worth it on the 331. I was already big-bored when I got my carb, but I did leave the CVK in for a few rides just so that I could tell what the difference was when I dropped in the FCR.
I did spend a good bit of effort fine tuning the FCR and it only got better after that.
#12
04-22-2008, 04:03 AM
RE: What would be better? Exhaust mod or bigbore?
I agree Brian....but the only one that posted with experience was ems...unless I missed a post and as far as I know he tried it on Marty's bike with the stock bore. I think the FCR really shines with the 340 jug...imho. Probably not much with a 250 jug.
#13
04-22-2008, 04:16 AM
RE: What would be better? Exhaust mod or bigbore?
I think I remember Eric saying he wasn't terribly impressed with Marty's setup. So maybe the effect of the FCR/Mikuni is more pronounced on the larger bore? So my advice based on this would be to definitely do the big bore first. Then upgrade to a pumper as time/funds allow. Of course, you'll want to get a pipe before any of that. If I was doing it all again, and I wasn't doing everything at once, I would do it in this order:
1) stage 1: grapevine mods: exhaust, airbox, rejet stock carb, drill the slide, all that stuff, ~$400
2) stage 2: kustom kraft 331 or Bill Blue 331 or Thumper 340 ... pick your poison, ~400-$800
3) stage 3: pumper carb - Jerry Leighton worked over FCR35 or Bill Blue worked over Mikuni TM33, maybe a TM36? ~$300-$600
4) stage 4: cams + port and polish, Shadetree style, ~??$$
1) stage 1: grapevine mods: exhaust, airbox, rejet stock carb, drill the slide, all that stuff, ~$400
2) stage 2: kustom kraft 331 or Bill Blue 331 or Thumper 340 ... pick your poison, ~400-$800
3) stage 3: pumper carb - Jerry Leighton worked over FCR35 or Bill Blue worked over Mikuni TM33, maybe a TM36? ~$300-$600
4) stage 4: cams + port and polish, Shadetree style, ~??$$
#14
04-22-2008, 04:22 AM
RE: What would be better? Exhaust mod or bigbore?
ORIGINAL: Nobrakes
Wow, I totally disagree with you guys on the carburetor. I can't speak for the Mikuni, but I had the FCR35 from Jerry Leighton and it really transformed the nature of the power delivery. Off the throttle was a burst of power and I mean with AUTHORITY. If you dump the clutch, one of two things is going to happen - either the front end will come up, or the rear wheel will break loose, there will be no in between. Not to say you can't control the power - you need to feather the clutch to do that, but if you want a snappy response, a pumper is the way to go, or more specifically, you want the slide directly connected to the throttle cable and not a butterfly valve and rely on engine vacuum to slowly raise the slide like the CVK.
I noticed a big difference in this when I switched out the CVK for the FCR on my 331. Maybe the one you guys tried wasn't jetted right or something or maybe the effect is more pronounced on a 331 than on a 250 and you only tried that setup? So maybe it's not worth it to pumperize a 250, I don't know, but it was definitely worth it on the 331. I was already big-bored when I got my carb, but I did leave the CVK in for a few rides just so that I could tell what the difference was when I dropped in the FCR.
I did spend a good bit of effort fine tuning the FCR and it only got better after that.
Wow, I totally disagree with you guys on the carburetor. I can't speak for the Mikuni, but I had the FCR35 from Jerry Leighton and it really transformed the nature of the power delivery. Off the throttle was a burst of power and I mean with AUTHORITY. If you dump the clutch, one of two things is going to happen - either the front end will come up, or the rear wheel will break loose, there will be no in between.
Not to say you can't control the power - you need to feather the clutch to do that, but if you want a snappy response, a pumper is the way to go, or more specifically, you want the slide directly connected to the throttle cable and not a butterfly valve and rely on engine vacuum to slowly raise the slide like the CVK.I noticed a big difference in this when I switched out the CVK for the FCR on my 331. Maybe the one you guys tried wasn't jetted right or something or maybe the effect is more pronounced on a 331 than on a 250 and you only tried that setup? So maybe it's not worth it to pumperize a 250, I don't know, but it was definitely worth it on the 331. I was already big-bored when I got my carb, but I did leave the CVK in for a few rides just so that I could tell what the difference was when I dropped in the FCR.
I did spend a good bit of effort fine tuning the FCR and it only got better after that.
Finger- you're like a gnat at times. I've ridden many bikes with pumpers, I know how they react. I make my recommendations on both experience and common sense. I'll send some of my pm's your way and let you answer the questions I get from members. That will help you make recommendations in the future, deal?
#15
04-22-2008, 09:33 AM
Join Date: May 2006
Location: Pittsburgh, PA
Posts: 12,584
RE: What would be better? Exhaust mod or bigbore?
ORIGINAL: Nobrakes
I think I remember Eric saying he wasn't terribly impressed with Marty's setup. So maybe the effect of the FCR/Mikuni is more pronounced on the larger bore?
I think I remember Eric saying he wasn't terribly impressed with Marty's setup. So maybe the effect of the FCR/Mikuni is more pronounced on the larger bore?
#16
04-23-2008, 04:29 AM
RE: What would be better? Exhaust mod or bigbore?
ORIGINAL: Nobrakes
If I was doing it all again, and I wasn't doing everything at once, I would do it in this order:
1) stage 1: grapevine mods: exhaust, airbox, rejet stock carb, drill the slide, all that stuff, ~$400
2) stage 2: kustom kraft 331 or Bill Blue 331 or Thumper 340 ... pick your poison, ~400-$800
3) stage 3: pumper carb - Jerry Leighton worked over FCR35 or Bill Blue worked over Mikuni TM33, maybe a TM36? ~$300-$600
4) stage 4: cams + port and polish, Shadetree style, ~??$$
If I was doing it all again, and I wasn't doing everything at once, I would do it in this order:
1) stage 1: grapevine mods: exhaust, airbox, rejet stock carb, drill the slide, all that stuff, ~$400
2) stage 2: kustom kraft 331 or Bill Blue 331 or Thumper 340 ... pick your poison, ~400-$800
3) stage 3: pumper carb - Jerry Leighton worked over FCR35 or Bill Blue worked over Mikuni TM33, maybe a TM36? ~$300-$600
4) stage 4: cams + port and polish, Shadetree style, ~??$$
I didn't have the pumper on the 250, but I've had both on the 300. The way I describe the pumper is; "it doesn't add more power, it just makes the power you have available right now". That assumption may be wrong, since I've had neither on the dyno. It's definitely a luxury for me, I really didn't need it for my riding conditions. No, it's not for sale. I love it for "on-road" riding, but it's hard on gas mileage and brakes. Yes, I really like to leave the lights like they're the tree at the dragstrip. When the stoplights are timed for normal automobile acceleration, I find myself braking a lot. I bet I look real silly rocketing to the next red light...too bad the little KLX is so much fun...
I plan on taking one of my cylinders out to 340, I think I'll pass on the cams. I've pretty much got my bike to where I thought it should be when it came from the factory. I'm just playing around now...
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