FMF Gnarly vs. Stock pipe comparison

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LOVEMYCR500
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Post by LOVEMYCR500 »

Oh 100hp Honda you so funny!!! Maybe it was the secretary, I don't know. why don't you buy one and tell us what the power spread is like.

My version of a clean up port will end up rasing and widening the ports a few mm's before it's over to match up the sleeve with the cast of the cylinder. I be a exhaust duration of around 192 with 32-35 degrees of blowdown time on the transfers and making the exhaust area about 65-70% of the bore would do pretty good for making upper end power but I don't want this. Since I haven't degreed in the motor yet with a degree wheel, I don't know what the stock port timings are yet. I don't hill climb or hill drag race with this bike so I don't need radical port timings. Once I'm done it will be plenty for me.

now my 431 cc puma 250r, that's a different story.
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Roostius_Maximus
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Post by Roostius_Maximus »

LOVEMYCR500 wrote: will end up rasing and widening the ports a few mm's before it's over to match up the sleeve with the cast of the cylinder. I be a exhaust duration of around 192 with 32-35 degrees of blowdown time on the transfers and making the exhaust area about 65-70% of the bore
give me a call before that grinding goes down
LOVEMYCR500
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Post by LOVEMYCR500 »

what suggestions do you have? Depending on the stock port timings which I'm sure are pretty low I wouldn't even begin to go this much on this motor. It's just a play around dune bike that I want to keep ridable and together.
LOVEMYCR500
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Post by LOVEMYCR500 »

100HP Honda, I just got done reading your post on the KTM 440 which has turned out real nice by the way and was looking at the port timings on the drag bike, okay I got to say my 192 on the exhaust duration looks tame compared to the 200 degree's on your drag bike. I thought I was pretty agressive at 196 degrees on my TRX puma on gas. I know they normally get up around 200 degrees on alky, you running alky through that thing?
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Post by 100hp honda »

which bike you talking ? my 440 is stock. packard did the work on one of my cr500 and i did my own porting on my other cr500.
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Post by 100hp honda »

you doing the porting yourself ? if so then i caution you against removing the bridge if that was your intenstions. once you take it out youve basically shot yourself in the foot because you cant put it back and if its not there it greatly reduces what you can do with the exhaust hole as far as height and width is concerned. its been a while since i scoped a stock cylinder but if i recall its already around 70% of the bore. seems like mine is about 100% of the bore but the bridge needs to remain intact to do it.
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Roostius_Maximus
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Post by Roostius_Maximus »

making the exhaust huge + wide is impressive looking, "porting" the area between the sleeve and the exhaust flange makes all the difference, theres a radius to it right now, changing that and keeping the stock port width, but extending its 10mm into the jug casting, steering the exhaust out of the port to match where the pipe is going to take it, then channeling the roof and taking the tumble off the floor makes more power than a giant belching wide port that spews all the pressure (power) out of the jug as fast as it can, make that sucker hold its squeeze longer, and cut the bridge out if its already cracked, teardrop the roof of the port so the ring comes back on it nice. making 80-90hp at 7000rpm is neat, but the guy making 15ftlbs more torque at 3500-6000 is going to be quicker, better on fuel, not as hot, and if you have to let off for something the engine will come back on instead of hanging under the rediculously high powerband the big port gave
LOVEMYCR500
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Post by LOVEMYCR500 »

#1. I won't do the actual porting myself, I would love to do the grinding but I'm too shaky to make it nice.

#2. Unless this was a full out drag bike, I would never take the exhaust bridge out. I will put a degree wheel on it stock and see what the port timings are before any port mapping will be done. Depending on the port area on the exhaust and transfers, if what you are are saying is true the exhaust port is already 70% of the bore, I wouldn't widen it at all and only raise it a couple mm's and then work on the exhaust snorkle as it leaves the port towards the pipe. I will make the boysen ports larger, and work on the transfers but not go to town on them. I want to keep a very broad power band.

I have never physically ported a cylinder, my buddy is real good at this part but I do think about what kind of power I want, do the research, moch them up and degree them we talk about it and he does the rest. I would love to do the porting as well but it wouldn't be pretty.

#4. I bought a piston from Glen and he talked to me on a few things as well.
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Post by 100hp honda »

Roostius_Maximus wrote:making the exhaust huge + wide is impressive looking, "porting" the area between the sleeve and the exhaust flange makes all the difference, theres a radius to it right now, changing that and keeping the stock port width, but extending its 10mm into the jug casting, steering the exhaust out of the port to match where the pipe is going to take it, then channeling the roof and taking the tumble off the floor makes more power than a giant belching wide port that spews all the pressure (power) out of the jug as fast as it can, make that sucker hold its squeeze longer, and cut the bridge out if its already cracked, teardrop the roof of the port so the ring comes back on it nice. making 80-90hp at 7000rpm is neat, but the guy making 15ftlbs more torque at 3500-6000 is going to be quicker, better on fuel, not as hot, and if you have to let off for something the engine will come back on instead of hanging under the rediculously high powerband the big port gave
shaving the exhaust floor flat is common routine :wink: . what you do with transfers and head ? dont tell me your running stock combustion chamber dimensions :D
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Roostius_Maximus
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Post by Roostius_Maximus »

:roll:
the af started with a cut down squish checked stock chamber head that worked fine, cut the other angle on it + .015 off the surface and it'll take more rev + is less eagar to ping but might not have as much down low, got another head on the bench thats angle milled .020" and has the chamber hacked out so i can move it to intake side of the cylinder :lol: might have to hack the water outlets completly off it and relocate them to the 3+9 o-clock locations cuz the plug is sitting between the 10+2. this was supposed to be a "trail" bike
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Roostius_Maximus
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Post by Roostius_Maximus »

the transfers are deffinately not as nice as they could be, they nolonger have the hook above the reed cage + the 2 closest to the exhasut are a couple mm wider

going completly flat on the exh floor is no good either, it likes to tumble and actually can slow it down if its not got a roll to it
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Post by 100hp honda »

LOVEMYCR500 wrote:#1. I won't do the actual porting myself, I would love to do the grinding but I'm too shaky to make it nice.

#2. Unless this was a full out drag bike, I would never take the exhaust bridge out. I will put a degree wheel on it stock and see what the port timings are before any port mapping will be done. Depending on the port area on the exhaust and transfers, if what you are are saying is true the exhaust port is already 70% of the bore, I wouldn't widen it at all and only raise it a couple mm's and then work on the exhaust snorkle as it leaves the port towards the pipe. I will make the boysen ports larger, and work on the transfers but not go to town on them. I want to keep a very broad power band.

I have never physically ported a cylinder, my buddy is real good at this part but I do think about what kind of power I want, do the research, moch them up and degree them we talk about it and he does the rest. I would love to do the porting as well but it wouldn't be pretty.

#4. I bought a piston from Glen and he talked to me on a few things as well.
if you want to run with the big dawgs let me know and ill get you a phone number. beware of shops that claim big numbers but cant produce :lol:

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agent
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Post by agent »

little more info. on the chart please, what kind of mods are we talking?

Rick
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Roostius_Maximus
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Post by Roostius_Maximus »

nice dyno


we went from the pipes, to trying to caution the dude on messing up the porting for his style riding, i havnet said anything of anybodys is wrong, i'm not going to make somebody think that theres 1 port job for everybody either. I know that if my AF bike didnt make power til up in the 6000rpm range i wouldnt ride it, i have an engine that likes that big rpm, its got its place, but that huge portwork can ruin a guys 500 experience pretty quick when trying to do anything other than compete with it. Keeping the port work conservative so its not having to blow more fuel out the exhaust to make the pipe work and adding big torque down low is going to make that thing useable everywhere AND decent on fuel stil.
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Post by dannygraves »

I found that opening up the boost ports was the single biggest thing to simply improve power all over. everything I did after that moved the power, but nothing made as much aditionaly power. I did my porting in stages...
first I did a general cleanup and opened the hell out of the boost ports and easily a %20 increase in power. the next time I widened the shit out of the exhaust and reshaped, that only slighly reduced my power right off idle and gave a good improvement in the midrange, but up top it still fell flat. the next time I drilled additional transfers and opened the hell out of the 4 main transfers. this brought back some bvottom and helped all the way across. infact, this is when it got hard to control down low. Then I added the 250cdi and thats when it started looping everywhere.
then I added a 41mm powerjet carb, had dewayne custom shape my head and installed a fmf fatty, at the same time I finally modified timing.. ~200* ex ~160*in
I also matchign the height on the upper boost port and angled it back some. now the thing is WICKED! and no one wants to ride it :lol:
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Post by Roostius_Maximus »

i would :lol:
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Post by dannygraves »

:wink:
'09 kx450f 4-Poke
Gen-4 trail bike --SOLD--
Gen-3 badass trail/mx bike --SOLD--
Gen-1 built dunes bike --SOLD--
'05 klx110 --SOLD--
'95 pw80
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LOVEMYCR500
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Post by LOVEMYCR500 »

thanks for the help and I will keep all this in mind. 100HP, my head was cut a long time ago and I went tame at 14:1 on the comp ratio. I didn't cut it, I had a local guy do the work that specializes in large single cylinder 2 strokes. If I were going all out on the porting on this, I would have him do all the work but this is a play around bike for me and I want to ride it and have fun with it. That dyno chart is impressive but I'm not going for peak hp on this bike. I already have the stock carb bored as large as I could get it, head is milled and rechambered, and all the other bolt on stuff is in place. Like I said, some guys have the skills to hold steady with the porting tools, I don't have them but I also have done a bunch of other motors over the years and will set this motor up right.

I have a 431 cc TRX puma that I am in the process of turning into a drag only bike, have a 250r play around bike, and the 500. I enjoy riding all of them.
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Post by 100hp honda »

agent wrote:little more info. on the chart please, what kind of mods are we talking?

Rick
you wondering if its trail freindly ? i wouldnt recomend it :lmao:
StinkFinger
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Post by StinkFinger »

Is there any video of that 89 hp beast on the net? I would sure like to see it in action!
1ugly85cr500
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Post by 1ugly85cr500 »

dannygraves wrote:FMF Fatty, or old regular gold series all the way. power characteristics like a stock pipe with a little more all over. :twisted:
I've got one of each and the gnarly is leaving with the next bike I sell. :wink:

my pipe says gold series on it no Gnarly or fatty on it I was always told that's a burley/gnarly with out the name were they wrong? Is it more like a fatty? Please explain a little more
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Rhino89523
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Post by Rhino89523 »

Just thought I would revisit this one. My Stock pipe got gouged pretty bad, dented really good, and then cracked really bad right where it makes the wrap in front of the ignition cover where it is two layers. Anyway I am in the process of fixing it and had to take the cover plate off to get at the crack that was under it, have that fixed and am rebuilding a cover plate, then I will knock the dents out paint it black and run it some more......If anyone has one of these garbage stockers laying around I am in the market.

Anyway in the process I ran out of time and decided to put on one of my other pipes for the weekend. I went with my old gnarly pipe that I repaired and had in stash....man I forgot what a pain they are to mount in comparison to the stocker. First its like a bar puzzle to get it in there twisting it around to get it to clear this and that, oh yeah it rubs on the radiator guards lets tweak those out of the way, oh yeah the rubber mount at the bottom either gets twisted like a pretzel or you have to make something else....where is that one I made for this? Dumping the box of shame on the floor spreads out to about 15 ft in circumfrance with parts from every bike I have torn apart in my short 40 year life. Digging I find the piece....don't tighten up anything until its all together so you can tweak it all to shape. I went to do it the way I put on the stocker.....I still have RTV residue on my hands. I am kind of looking forward to riding it...where I'm going grunt is good, I still wish I was on my stocker.
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2strokeforever
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Post by 2strokeforever »

my gnarly fits fine
the 450 will have less power and will be harder to start, and will be heavier, but to make up for it it will require more maintenance.
4stroke=dead fish
Redlined
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Post by Redlined »

1ugly85cr500 wrote:
dannygraves wrote:FMF Fatty, or old regular gold series all the way. power characteristics like a stock pipe with a little more all over. :twisted:
I've got one of each and the gnarly is leaving with the next bike I sell. :wink:

my pipe says gold series on it no Gnarly or fatty on it I was always told that's a burley/gnarly with out the name were they wrong? Is it more like a fatty? Please explain a little more
If I remember correctly those are similar to if not the same as the Fatty. I ordered one for my old YZ back in the 90's, they were calling them Fat-Boys I think, but the pipe arrived and only said Gold Series.
I've got a Gnarly on my AFC, haven't ridden it enough yet to have an opinion, but I prefer the OEM pipe on my CR250, the Gnarly nuetered the top-end on the 250. I'll try something else once I crush the Gnarly
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NightBiker07
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Post by NightBiker07 »

My bike came with a PC. I couldnt imagine this thing having more low-mid power. revving it out make the bike feel slow, so I'm not sure what you guys mean by the PC having good top-end. But, all Im comparing to is my 250, and that thing was all upper-mid and top end power, you had to rev it out. I short shift the 500 like a mofo, and that keeps it accelerating hard.
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