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Jetting with gnarly/shorty

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I just ordered a fmf gnarly with a shorty muffler for my 05 yz250. I d'like to know what are the "cummon" jetting change ill need to do. My bike run well with stock pipe at the moment (a bit rich but good). Does the fmf pipe will require leaner or richer jetting?

Ty for the advice!! 👍

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For me, it was richer on my 03. I had more mods than just a pipe for my bike though. I'm in the process right now jetting my bike.

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Every gnarly user I've spoken to runs 1-2 steps leaner than the chart in the jetting post at the top of the section says (pg 7)

You should notice the bottom sharpen up and the top not fall off so abruptly by experimenting with this.

All bikes are slightly different, but FMF and my experience recommend leaner.

Sometimes moving one jet size gives the wrong impression because of the small change.

If you're at 175 say, you can run a 180 vs. a 170 and really clear up any confusion which way was best by going with a 2 step check.

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More Velosity means leaner jetting not richer!!! 172 main, 48 pilot and get Klotz R50 and run it 50:1

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Frank, what are your altitude, temperature, type of riding?

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I do mostly sand dune / wood riding. I usualy run in the range of 60 to 80F. and im about at sea level.

Thanks for all your advice

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Frank, because you are running near 60F sometimes and with the sea level, gnarly and sand,

go with 48/175. The 172 would be fine except for the sand.

Imho you need a little more fuel for cooling/detonation in that condition so the 175 would be better..

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Every gnarly user I've spoken to runs 1-2 steps leaner than the chart in the jetting post at the top of the section says (pg 7)

You should notice the bottom sharpen up and the top not fall off so abruptly by experimenting with this.

All bikes are slightly different, but FMF and my experience recommend leaner.

Sometimes moving one jet size gives the wrong impression because of the small change.

If you're at 175 say, you can run a 180 vs. a 170 and really clear up any confusion which way was best by going with a 2 step check.

if my optimum jetting for the stocker pipe is at 45 pilot and 172 main jets (plus assuming N3CW at 2nd clip) does it mean that when i re-install my gnarly and powercore combo, i need to lean out to 40-41 pilot and 168-170 main 👍

i thought the gnarly pipe was already homey with my present set-up (N3EW, 2nd clip, at present) based on the stocker pipe when i installed it the first time last may 2008, although it was too early to tell as i tested the set-up only once.

...same observation also goes with the DEP header pipe and the stock silencer. thought i didn't need to rejet.

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If your riding/bike ran best on the 45/172 stock, I'd go 42/170, or 42/168 on warmer days, with the gnarly.

Both reported jetting and FMF recommend one step leaner with the gnarly.

The needle could prob. be dropped to the #1 3EW at that point although you may

either need to pull a degree of timing, richen the A/S or go back to the #2 3CW for minor detonation.

Of course if you got any detonation above about 2/3 throttle, I'd also go back to the next bigger main too.

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