TE/TC Inside scoop FMF "long" Jarvis muffler

lots of intertube gossip about the super long, (long smooth power) Jarvis FMF muffler seen on his competition machines.

Direct (very) word is, we may soon see it as an addition to the regular riders menu on the FMF site soon. If so I for one am in. I have been running my OEM muffler to get close to that lonf electric smooth power, my FMF turbine core actually hits harder than the OEM muffler.
When released the long FMF "2.1" can will be lighter as well as very quiet compared to the OEM muffler. Like the OEM muffler it will be a non S/A pipe, I'm sure there will be some sort of cap to add for S/A compliance if needed, either from FMF or another supplier like EE for example.

side note, talking about Jarvis you all may see a really shape strange FMF entire pipe/chamber on his extreme race bike as well.

i noticed that his pipe looks way different than stock. custom FMF

Thought I read it's a 4 stroke muffler modded to fit.

most likely will be called Powercore 2.1,
I'm in when and if it's added to the retail catalog.

I think it's just that, gossip. Long silencer does not make long smooth power like on a 4 stroke.

hate to disagree with an expert but I have used shorter mufflers and long Aussie WR muffler on a CR and WR 125s and it gives a longer , smoother power delivery in my opinion

I'm pretty sure you've got it wrong, I've changed the length of the muffler on a 2T 300 a few times & the power delivery was different with every change of length.

I have used many different lengths of silencers and or stinger lengths on my 165 - 144 - 125 and yes they all made a difference, The item I use now adds about 2" to the total length and make for a smoother slightly more low end type of power, If I go any longer the top end suffers and brings on a little detonation as a by product - Perhaps making the engine run hotter !!!

for sure, the silencer on a two stroke is just an extension of the stinger. longer tends to choke down top end and limit rpm, but boosts bottom and mid. cutting down the silencer usually does the opposite.
of course there are exceptions, where you have a very restrictive muffler and replace it with a different unit thats shorter you may gain everywhere. its just kind of a guideline. changing silencer length with everything else equal is definitely a tuning tool..

Optimum stinger length and its diameter, which should include the added length of the silencer and no more ideally. Makes all the difference in the world when building 2 stroke pipes. Done about 200 of them since 1975 or so. For everything from 80cc to 500cc Flatrackers to TT racers, Motocrossers for both 2 wheelers and Quads. Power valve equipped 2 stroke Motocross bike engine swaps into quad frames also, Like KX250s,KX500s, RM250s, CR250s, CR 500s, all swapped into quad frames. Even Banshee engines into early Gray Quadracer chassis mostly set up for shorttrack, Flatrack and TT racing. Sometimes for rough scrambles type racing also.

Pipes for Vintage early Maico's were a specialty.

I currently use the "2 stroke wizard" software nowadays. Much easier than the map out the ports and punch into the calculator method of days gone by. All hand rolled cones. some as many as 60+ individual, separate pieces. Can you say "manual projection layout" for each cone section. I usually matched all the seams too.

Unless building a pipe for one of my old Maico's for a restoration. You couldn't pay me enough to do this anymore. It's a lot of long tedious work that is greatly un-appreciated. Kind of like when I used to build Custom Western hand tooled saddles.

Used to build custom pipes from provided specs from Kuykendahl Performance who was a 2 stroke tuner for "King Kenny Roberts". When he specified a particular overall stinger length on one of his pipes and he was very specific about it. I didn't mess with that length, he didn't care if the silencer ended up in the top side of the airbox on a quad and it did a few times. The airbox lid would be then refabricated, insulated with reflective insulation tape and the original airbox lid put away in a drawer somewhere. Quad chassis were especially difficult to build pipes on some of engine swaps for. Sometimes requiring doubled slip fit cones, spring loaded and secured mid stream in the pipe itself to fit on the chassis and still be able to be removed. The silencer's would all be hand made as well and packed so tightly it was like a straight piece of tube. The engine would hardly know it was on there but overall length was absolutely critical for optimal results with regard to port work and head modifications.

Kuykendahl designed all the production pipes for the Suzuki 2 stroke RM series of bikes from the beginning in 76'.

Also built more than a 150 production pipes for John Cowgill at "Quad Dynamics" in Stockton CA. I did several 1 of a kind custom pipes in every conceivable configuration for him and many others that were racing at the Lodi Cycle Bowl up in the Central Valley in CA. In the late 80's to early 90's.

Stinger length changes make for optimum power delivery that can change drastically up or down through the available powerband window. Saying it doesn't have any affect is like saying it doesn't make any difference cutting the pipe right down the middle of the belly and adding or removing a straight section of an inch or less for top end power or mid range grunt.

Length matters on any stroke!

PS this was only an info thread to let everyone know that most likely FMF will market/retail the PowerCore "2.1" xtra long version of the Powercore 2 muffler. The XL version seen in fotos on Grahams bike was custom made for him.

yea and if its only gona take 2 the length better be i had a friend[rip]we called him 2 stroke 1, 4 u 1, 4 me thats he wood say i sure miss him he was a true friend

i appreciate this work greatly, im very happy dynoport is around to make all the liquid cooled husky pipes..the fit and workmanship is great as well.

yea but they dont have a mailbox at the shop i,v been waiting 2 weeks for rich to go to the PO to get the S/A screen i sent so he can make mine and their always two weeks behind he must make a buttload of sled pipes

I always ran the longer Husky Euro spec/ non Sparky silencer on my '09 WR125, instead of the CR125 shorty that US spec bikes came with. I had zero problems with my jetting, compared to most guys' '09 WR125's on this forum. Bike ran super smooth from bottom to top.

90 percent of their business is snowmobile, you probably picked their busiest time of the year!
rich does a nice job tho. lil thicker than other brands as well.

oh yea i have a full set up on my KDX trouble is Cobra stopped making the sparky so no more S/As i came up with a FMF screen that has a USFS # on it