Making an FMF Shorty from an FMF PowerCore II HOW TO

[Joshmcmillan]

Hey guys, one of my friends mentioned he had done this to the FMF from his CR years ago, so I decided to give it a try and here's how I done it.


1. Screw out the two rivets at the rear of the pipe using a 1/8" drill bit. You can leave the end-cap in there.

2. Use a piece of tape to help line up where you're going to cut. I'd go as close as you can to the mounting point (I didn't, and it definitely isn't TOO loud).

3. Cut your shiny FMF muffler in half, as well as the packing material, you can leave the pipe in the center.

4. Use a long flat-head screw drive or pry bar and a mallet to tap out the exhaust end-cap, as you'll be needing it.



5 . Now you need to remove all the remaining packing.

6. Undo the three allen key bolts at the back of the pipe, and use a screw driver or pry bar and mallet to tap out the other end.

7. You need to cut the main exhaust pipe a bit shorter than the length of the outer tubing, as shown in the picture below. This is to allow the end-cap to slide on far enough. Make sure that the cap slides over the end easily, you might need to smooth off your cutted edge.



8. Wrap the silencer packing material back around the remaining part of your pipe, and slide the outer material back on. I tapped mine on some wood till it was on far enough and the holes for the screws lined up. Tighten the screws.

9. Place the inner part of the end cap over the pipe to make sure it slides on and you've cut the inner pipe to the right length.

10. You'll need to line up the holes in the end-cap with the outer tubing and mark about where the holes will need to be. Drill a whole the size of an appropriate pop rivet you have. (I just roughly drilled my hole and opened up any slight differences after)

11. Now for by far the hardest part, put the endcap back on. I didn't find any real trick to this, but it took me quite some time to get it all lined up and started so I could tap it on. I even ground a bit down on the inner side of the outer tubing to make it easier.

12. Once it's on, pop rivet it all together, smooth off any edges and away you go.





Looks better, doesn't get smashed on rocks and stuff as easily when you drop it. Sounds a bit more refined/deep at idle, and a bit louder. Overall worth the short amount of time/effort and zero cost :)

[newbbewb]

Nice! funny you mention this mod, with the little time I have right now for dirt bikes, I'm cutting up an FMF sparky for a kdx250 and making a sparky for the kx200.

I like to use rtv on the both endcaps and rivets to prevent the spooge from leaking.

[bufftester]

Hew Newb, keep in mind that at least in WA state, if you modify a spark arrestor (not just a silencer like the power core) that you could face a pretty steep fine if tagged by the rangers in a check (and they DO check, I have been in the middle of nowhere at Taneum creek and had rangers ride up and do sound checks). Also, if you do shorten your silencer, it may not pass sound checks for your area, and right now sound is one of the hottest buttons for banning our sport from public lands. For those of you in other parts of the world it may be a non-issue, but at least check first before cutting up that pretty 200$ hunk of aluminum.

[newbbewb]

Thanks for the heads up, didn't realize sound was such a big issue. I'm making it the same EXACT size as the FMF sparky for the E series, which happens to bolt onto the kx200. The KDX250 FMF sparky has seen better days, so won't be sad. As far as for them checking it, it WILL be a spark arrestor, and it will be quiet. I'll even be able to cut it up so that the laser engraved USFS notice will show. If I get a ticket, then that will be one educated smoky, and I'll blame it on anyone that rides a stock KDX250, because they didn't buy it when I had it for sale :)

[Joshmcmillan]

We have similar rules here, but I've never even seen a ranger.
This didn't really make it much louder, definitely slightly more 2-stroke sounding but nothing that anyone other than a KDX owner would notice over the normal fmf. I think it looks a lot better tho!

[ICRage42]

yea I ride almost all private land around a state park. I had a ranger following me. He waited till I got my bike loaded one day and was going down the road. I had to put fuel in and start it up and he hit it with a decibal meter. Stock silencer and aftermarket exhaust expansion and I just passed. Yea not fun. This guy was watching me for a week and kept getting closer. I wound up getting a stock silencer off of here and it wasn't a week later I got hit. Good thing too the one I had didn't have a spark arrestor and it was considerably louder then stock sound. It would of been a good 500 dollar fine Im sure.

Now that he stopped me I haven't once been bothered by him again. He sees me just gives a quick glare and walks away now.

It just takes once to get ya really. With any violations it just causes hell for a lot of other things too Ive found out. You get problems with getting hunting licenses. I do believe in some states it also reflects on your insurance. Ive heard horror stories from people going to pa from ohio here and let me tell you they had to pay more in insurance caused them not to hunt. All kinds of problems that no one really wants. In PA they are really strict. Try hauling a bike to ride with a modified or aftermarket silencer without spark arrestor. They look for that all the time. I don't know if its because I have Ohio plates but I always get a once over when going to my favorite park.

Private land riding wont get you into any worries or mx track but public riding areas you gotta follow the rules.

Nice mod tho good info for sure!

[6 Riders]

yea I ride almost all private land around a state park. I had a ranger following me. He waited till I got my bike loaded one day and was going down the road.

Sorry but I would have told him to "go Fluck himself"...Bikes in trucks don't need to meet ANY sound restrictions or have spark arrestors. What a WAD! (not you, him).

I'm not anti-law enforcement, I am anti-Power trip ****-wad cop that want's to make a point! Guy was either bullied in high school, or the bully and just can't let H.S. go.

[newbbewb]

I got a ticket for ORV tag being expired by three days here in WA. I neglected to take care of it right away and forgot about it. 3 months later I got a notice that my license was going to be suspended unless I took care of it. Fair enough, I paid the stinking fine and everything was good until my auto insurance went up $10 a month because of the ticket. It was a non-moving violation, I'll be damned if I stop ever again, come get me.