FMF Silencer for 400/520 EXC

Joined
Jun 5, 2001
Messages
65
Likes
0
#1
Hey all - I searched and found nothing on FMF exhausts for KTM 4-strokes. Has anyone had any luck with the FMF Powercore IV SA or the new Powercore IV Q (quiet series). I would be interested in getting one of these, but would like to hear of other's experiences first. I have always had the most success with FMF products, but I know the aftermarket is having a heck of a time improving an already fine performing 400 or 520. I heard Lafferty runs a KTM SX silencer on his 400 for a little more ooomph, but I really like the way the FMF's look and sound. I guess bottom line is I am not paying $300 for no increase in perfromance!! Thanks!!:cool:
 

jeb

Member
Joined
Jul 21, 1999
Messages
633
Likes
0
#2
Most people are running the stock exhaust so I haven't heard much about performance comparisons going to the aftermarket ones except the one you mentioned, using the KTM SX silencer. All of the aftermarket silencers I've heard about, even the quiet ones, are anywhere from much louder than stock to way louder than stock. I won't add to dirtbikers already long list of problems by making my bike any louder.

You should try rejetting the bike first. Use the OCEMN needle in the middle position (#4), 1 turn out on the airscrew, 168-170 main, stock pilot. It gives the bike a noticeable but not dramatic increase in power in the low to mid range. Makes 3rd gears wheelies, for example, much easier to do.
 
Joined
Jun 5, 2001
Messages
65
Likes
0
#3
Hey Thanks Jeb!! Yeah, I hear ya' - I definitely don't want to make the bike any louder and give our sport a bad name. I have heard good things about the new FMF Quietcore though. It supposedly brings the Yamaha 4-strokes to meet the USFS/State sound requirements - impressive if true!!

Thanks for the jetting specs. I trust this is what you run on your '01 400 EXC? I am looking for just that - a little more ooomph! I don't expect (nor want) to transform it into a fire-breather. Do you run different jetting combos for different conditions or have you settled on the specs you gave in your post? Also, do you run pump or race gas? Thanks Jeb!!
 

jeb

Member
Joined
Jul 21, 1999
Messages
633
Likes
0
#4
Yes, those are the specs I currently run. I'm using a 170 main but you may want to play with that. Seems luggers like me like fatter mains where screamers might get more out of the leaner ones. Like you, I didn't want to have YZ4xx type of power. This spec just makes a nice woods powerband into a perfect one.

This is the only spec I run and I only run 92 octane pump premium. We don't vary much in elevation here in the upper Midwest so it's not a problem. It seems to have improved the mileage, too. A win-win.
 

KTMMIKE

Lifetime Sponsor
Joined
Apr 27, 2000
Messages
29
Likes
0
#5
I had a '01 400SX for awhile. It was completely stock. I rode a friends '01 400SX with a FMF PC IV Quiet series. It also was completely stock (except the FMF addition). I liked it alot better. It was more responsive down low & pulled OK on top. Mine did seem to be better on top. But I would much rather have the FMF feel. If anything it seemed quieter than my stock exhaust.
 
Joined
Jun 5, 2001
Messages
65
Likes
0
#6
Thanks for the input fellas! Hey Jeb - I've never worked on an FCR carb (only PJ, PWK, TMX and the such). Anything I should know before I go ripping things apart? Thanks again!!:scream:
 

jeb

Member
Joined
Jul 21, 1999
Messages
633
Likes
0
#7
Originally posted by KTMMIKE
I had a '01 400SX for awhile. It was completely stock. I rode a friends '01 400SX with a FMF PC IV Quiet series. It also was completely stock (except the FMF addition). I liked it alot better. It was more responsive down low & pulled OK on top. Mine did seem to be better on top. But I would much rather have the FMF feel. If anything it seemed quieter than my stock exhaust.
Thanks Mike. Good to hear some of the quiet ones actually are! How much louder is the SX silencer than the EXC? I didn't notice a whole lot of difference when we rode together in Missouri in Feb. Still got those 2 new RFS's sitting around? I may know someone interested in the 400EXC.
 

jeb

Member
Joined
Jul 21, 1999
Messages
633
Likes
0
#8
Originally posted by triplephatmx
Hey Jeb - I've never worked on an FCR carb (only PJ, PWK, TMX and the such). Anything I should know before I go ripping things apart?
A couple of things. You'll have to take the seat and tank off to work on the carb. The best way, not easiest, to get the carb out and back in is take the rear hose clamp all the way off and man handle the airboot. The easiest way is to take the seat off, loosen the rear hose clamp on the carb, remove the 2 lower subframe bolts and swing the subframe with the airboot up and away from the carb.

You'll also have to remove the crankcase vent line from the exhaust side of the carb. Take the accelerator pump apart while you have the carb off and make sure it's clean. The top side of the diaphram gets dirty.

When you re-install it, make sure the plastic cover on the exhaust side is not touching the exhaust pipes. Experience talking here. I burned the bottom part of that guard off already. ;) You can change the main and pilot without removing the carb by just loosening the carb and tilting the top towards the exhaust (make sure those pipes aren't too hot!).
 

KTMMIKE

Lifetime Sponsor
Joined
Apr 27, 2000
Messages
29
Likes
0
#9
jeb-When we rode together at Chadwick I was running an EXC silencer so I would have a spark arrestor. The SX silencer is quite a bit louder than the EXC.

The only RFS we have is a 400EXC.
 

Shaw520

Damn Yankees
Joined
May 14, 2000
Messages
1,082
Likes
5
#10
The SX silencer is alot louder than EXC,... to find and aftermarket pipe that makes more power, and is as quiet as the stock EXC pipe, would be next to impossible. In fact, the little gained from a louder aftermarket, is not worth the money or the decibles. I have two riding buddies that have put FMF's on their RFS's with almost no noticable difference, except of course the noise. Some guys claim the EXC's are too quiet, and for this reason go out and spend $285 on a pipe. If this is the case, remove the wads (2) of packing from the silencer and you will then hear your bike.
Oh yea, and those guys that put the FMF's on, can no longer get their hands between the pipe and the sub-frame to lift their bikes. Go figure.:think
 

trewent

Subscriber
Joined
May 26, 2000
Messages
72
Likes
0
#11
I put a SX silencer on my '00 400 exc, it woke up the power a bit, revved quicker and was alot louder, I'll run it when riding MX, but for trails I like the stealthness of the EXC pipe, the FMF Q series looks like the Euro technology KTM uses on its EXC's over the pond. By the by, a friend put the EXC pipe from my 400 on his 520 SX, claimed it made the midrange much more potent, cut top a little, I found that the 520 became much more manageable, this big low end rush smoothed out, but it still has monster torque. I was thinking about a 520 for a bit and decided to stick with the 400 for another season. Although putting a 520 P/C on the 400 is still a curiousity question for me.
another .02:cool: