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TimR

Physical differences between fmf fatty and gnarly?

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I have an 18' 300re. I was wondering which pipe was stocker, so I called fmf and gave them the part number on the stocker, 125081. They said that it pulled up as a fatty pipe built for beta. So I wanted to try a gnarly for my woods riding. Got one in today and after looking at it and the stocker, measuring length of sections, circumference of sections, it seems to be identical to the stock pipe. So I called fmf back up and got a different person this time. Asked him to look up the stock part number and he also said it is a fatty. Explained to him the gnarly I got was identical. So he looked up individual part numbers for each section of the pipe. Come to find out, the stock pipe and gnarly have the same parts. He then looked up the fatty and different part numbers. So the stock pipe is a gnarly according to the individual pipe section part numbers. I just wanted to be sure. Has anyone ordered or actually seen a fatty and a gnarly side by side? Where is the difference in the 2 pipes. Here are some pics of the stock, on the left and the gnarly. 

20190108_153158.jpg

20190108_153314.jpg

20190108_153408.jpg

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the stock and the gnarly are def not the same pipe. I have a gnarly on now after damaging my stocker. A little more low end but signs off earlier on the top. From what I've read, the fatty and gnarly are very similar except the taper back to the stinger that attaches to the silencer. that's why carbon fiber guards still fit all the same

Edited by randysoo
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Randy, I believe you, but I just can't find any difference in the two. Even measuring them. I haven't tried it on the bike. Just didn't want to waste the money if no different. 

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We’ve gone through a bunch of stock pipes and Fatty’s.  Never have been able to tell a difference in any dimensions or performance. 

Tried Gnarly’s a couple years ago. Other than the fact that it’s thicker and plated couldn’t tell any difference. 

I know a lot of people will argue this point, but other than the thickness and plating I wouldn’t be surprised at all to know they are all the same pipe.  I know we’ve gone through more pipes than anyone on this forum. When Ty ran FMF it didn’t matter which version it was, they all worked the same.

I never said that in the past because I know everyone will disagree 😂

 

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Is the one with the fresh, green orings the fatty?  Hard to tell in the pics but it looks like the one with the black orings has a longer head pipe.

A pipe designed for low end will generally have a longer head pipe and/or longer overall length. 

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7 minutes ago, turbo dan said:

Is the one with the fresh, green orings the fatty?  Hard to tell in the pics but it looks like the one with the black orings has a longer head pipe.

A pipe designed for low end will generally have a longer head pipe and/or longer overall length. 

Dan, the ones with the fresh new orings is the new gnarly, other is my stock pipe. It's hard to tell with pics due to angle of camera. I measured every weld of every section. No difference anywhere. 

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17 minutes ago, Cullins said:

We’ve gone through a bunch of stock pipes and Fatty’s.  Never have been able to tell a difference in any dimensions or performance. 

Tried Gnarly’s a couple years ago. Other than the fact that it’s thicker and plated couldn’t tell any difference. 

I know a lot of people will argue this point, but other than the thickness and plating I wouldn’t be surprised at all to know they are all the same pipe.  I know we’ve gone through more pipes than anyone on this forum. When Ty ran FMF it didn’t matter which version it was, they all worked the same.

I never said that in the past because I know everyone will disagree 😂

 

If they measure the same and same shape, how can they run differently? 

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7 minutes ago, TimR said:

If they measure the same and same shape, how can they run differently? 

They don’t. 

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Posted (edited)

The only real solution here is to also order a Fatty and see if it matches the Gnarly you bought, and also the stock pipe.  😂

Edited by mbrick

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Have you tried measuring the volume of each? Plug one end, fill completely with water, then dump it in a measuring cup and see how many cc’s each pipe is.

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I was always under the impression that gnarly pipes and fatty pipes were almost the same the only difference was the thickness of the pipes material? 

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Posted (edited)

I have both a Gnarly and Fatty for my KTM 300 XC-W. Gnarly was on the bike when I bought it. Yes the Gnarly's made out of thicker Steel, it also has more hit down low and signs off much sooner than the Fatty. The Fatty has much more over rev and broader power band. I run the Fatty 90% of the time. On my KTM there's a very noticeable difference.

Edited by racesla
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I have a 2001 CR250R and I have all three. A fatty, A gnarly, and a SST. and yes they all are different. The fatty imitates stock pretty well, The gnarly will actually chug out of turns . and the SST will loose a bit in the  bottom and going to the mid range will pull to the sky. Ed Shiedler of Yamaha once said " there is not an error in porting that cannot be repaired with a pipe, and there is not an error in the pipe than cannot be repaired with porting" Just a quote. In the late 60s and 70s before going to work for Yamaha Ed was well known for his expansion chambers in SoCal.

CR

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Yeah I’m sure the pipes are different for other brands of bikes. For the Beta not so much. 

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I've got a spare stock pipe and a Gnarly in my garage. I'm waiting on one of those Hydraforce kits, and then I'll measure with water, since I'll need to fill 2 of them up regardless.

Also, if the outsides are the exact same measurements, but the Gnarly is thicker - then the Gnarly will have a slightly smaller inside diameter. I'd guess it's negligible, but I have limited knowledge about two strike pipe design. I don't even know what the thickness difference between the 2 are. I just know you can feel the weight difference when you pick both up at the same time.

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Been through this with GGs and talked to Kevin Hines at ELine about it some years back.  What FMF does in many cases is just build a Gnarly and Fatty to the same spec but with 18ga steel vs  19ga.  They also have a std collection of section stampings, they use to build a pipe with if possible, so in some cases a pipe guard from a completely different bike will fit.  Bottom line is like Chris said there are not two different pipes each custom engineered for Beta applications and GG for sure as I have verified.

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