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Making an fmf q stealth for my cr500

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well i've been wanting to do this for a while now and i finally pulled the trigger. I'm fitting an fmf q stealth for an 02-07 cr250 on my cr500. the inner core and mid pipe have to be up sized so it takes a fair amount of work. my bike is a 2006 cr500af. it built on a crf250r chassis. the goal is a quiet throaty sound and a spark arrestor not to mention it will just look cool and fit the custom theme of the bike.

cr250 mid pipe

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cr500 mid pipe

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the core for the cr250 is 1" and the cr500 is 1.25". i bought some 1.25" stock

3CD83386-4D26-47E9-8577-626FD0495141_zps

here is the new pipe that i hacked into. it was part of a trade so i don't feel too bad hacking it up. it's going to look nice on my gen 4 conversion. i'm really curious what it will sound like? the mounts are in the same spot as a cr500 silencer so at least thats easy

D3281285-37C7-4A81-A11F-0D0F72E10B54_zps

had to pull the end cap and spark arrestor out in order to enlarge the hole to accept the larger core. i just used a die grinder and it was quick and easy.
i was then able to re-install the end cap with some new SS rivets

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i then pulled the mid pipe end off the Q stealth off and removed the core and mid pipe with a cut off wheel. i then upsized the hole in the cap to accept the larger mid pipe.

 

46EA0AA0-8036-402A-B742-7C5D92251A62_zps

i got it mocked up for a test fit. it will require some spacers which my buddy is making me tonight. this will get the larger can far enough from the rear wheel but still has nice clearance from the number plate. the cr250 mounts are indeed the same as as a cr500.

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i also got the mid pipe tacked in place and will finish the welding tonight. then i just need to weld the larger core in place and put the packing back in and shes done.

97DC576D-873C-49EB-8344-F52341D1F71E_zps

 

 

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guess you gotta drop $10,000 bolting titanium and carbon fiber on a bike to get a reply these days huh?  :lame:

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Cool set up, seems excessive though, cut the 500 mid pipe off and weld it in place of the 250 mid pipe. Strip the paint and be done with it

had to uspize the core as well from 1" to 1.25" so the 500 can breathe! also had to not only change the size of the mid pipe but also the angle of the mid pipe to clear the rear wheel and line up with the mounts.. the first donor pipe i bought of ebay was an oem silencer from a 1991 cr500. it wouldn't work because the damn thing was all aluminum and the core and end cap are steel. i found another steel mid pipe off a cr500 but i had to add 1" in length and change the angle. nothing excessive just what needed to happen to do it right. a few guys tried to just leave the smaller core and it was too restrictive.  almost done

 

 

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FCB4AC8A-8954-449D-A422-F52B8353581D_zps

Edited by rodgini
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My CR500af came with a Q-Stealth on it (I didn't build the bike). I haven't analyzed how they did it, or what the silencer was originally for, but it does not appear to have been altered.

Edited by Redlined

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My CR500af came with a Q-Stealth on it (I didn't build the bike). I haven't analyzed how they did it, or what the silencer was originally for, but it does not appear to have been altered.

Maybe you have a q but not a q stealth? Got a picture? The mid pipe has to be upsized as the cr250 mid pipe won't mate to a cr500 expansion chamber. I know Fmf definitely doesn't make a q stealth for the cr500 but they do make a standard q.

 

edi- also- fmf doesn't make any q stealth pipes with a larger mid pipe. the largest bore bike they make it for is a euro 300 and they have the same size mid pipe and core as a 250. also note- not only is the core larger diameter but the holes are much larger. either you have a standard q or somebody did a nice job modifying a q stealth.

Edited by rodgini

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Good job.  Where did you find the perforated tubing?

 

So the stealth is a normal glasspack plus a spark arrester?  With a name like stealth I was expecting a baffle. 

 

FMF also doesn't make a stealth for the early steel frames so I've been thinking about altering a later year muffler.  By the time I alter the inlet tubing and the mounting brackets, it might be no more work to just extend the existing core and body tubing.

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Looking good. Looking forward to a vid clip of the Q Stealth 500AF. It's gonna be deep sounding! Oddly I've seen a few Euro 125s with the Q Stealth so no reason to restrict them to just the 250s! 

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Good job.  Where did you find the perforated tubing?

 

So the stealth is a normal glasspack plus a spark arrester?  With a name like stealth I was expecting a baffle. 

 

FMF also doesn't make a stealth for the early steel frames so I've been thinking about altering a later year muffler.  By the time I alter the inlet tubing and the mounting brackets, it might be no more work to just extend the existing core and body tubing.

i got the tubing from these guys-

 

http://www.cruisercustomizing.com/1-x-24-inch-perforated-stainless-baffle-tubing/part/LA-1210-24

 

the q stealth is the same as the q really with a turbine style arrestor. however the can is larger in diameter and holds more packing.

 

do you have a steel frame 500 or 250?

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Good call on the larger inner pipe diameter.

I to found it to be to restrictive when I did he same mod on my cr 500afc. Thanks for the link. Now I know were to get the inne r pipe.

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i got the tubing from these guys-

 

http://www.cruisercustomizing.com/1-x-24-inch-perforated-stainless-baffle-tubing/part/LA-1210-24

 

the q stealth is the same as the q really with a turbine style arrestor. however the can is larger in diameter and holds more packing.

 

do you have a steel frame 500 or 250?

 

I have a steel framed 250.  So the core would be the correct diameter, but I'd need to fab new mounting brackets and reshape the input tubing.

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I have a steel framed 250.  So the core would be the correct diameter, but I'd need to fab new mounting brackets and reshape the input tubing.

Gotcha. Well the mounts for the 02-07 cr250 line right up with the 89-01 steel frame cr500 as that is where I put my mounts when I did the af conversion. You might not have to move any mounts if you get lucky? I have a brand new mid pipe off the stealth that I chopped off. If you want to Experiment with it just pm your address and I'll mail it to ya.

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Thanks for the offer.  I'll take some measurements and get back to you on that.

 

If indeed the steel frame CR250 mounts match those of the '02-'07 CR250, that would save some fabbing.

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here are a few more pics.

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and a video. sound is a subjective thing really. it is quieter than the DEP enduro pipe i was running. i can hear the engine noise much more than the exhaust now. no noticeable change in power delivery. i'll get some go pro footage as soon as i can.

th_IMG_1332_zps4f301fbe.jpg


 

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Nice work, nice bike too...Is that set up for trails, I was thinking it was a dez rig but saw your from Virginia.

 

Thanks man. Yeah it's my do it all bike. We primarily trail ride these days but she does just fine on an mx track. I just had to up my fitness leveI to be able to ride it for a 30 minute moto on the track. I'm 6'2" tall 200 lbs and that helps. I built it as a novelty project but once i rode it I fell in love. It has good manners and if it starts getting unruly you just shift it up a gear and things smooth back out. I ride goat trail style off camber single track on it no problem and i'm just as fast as i was on my 2008 yz250. A 250 2-stroke feels anemic and hyper to me now. I'm addicted to the big bore 2-stroke. My next build will be a cr500 in a modern ktm chassis with a linkage. Here's my list of trail friendly mods-

 

magura clutch with midwest mountain engineering lever

2011 brembo front master cylinder with midwest mountain engineering lever

170mm front rotor

18" rear wheel

acerbis oversized tank

gpr v4 stabilizer

flexx bars

tall seat

pmb kick stand

38mm smart carb

porting and squish adjusmtent

decomp button on head

DIY suspension re-vavle for woods riding w/ RT gold valves

fmf q stealth with a fatty up front

mohard racing rad cages and various off road armor

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There were a couple guys out here in Hawaii that tried the af500 for trail but the bike was too much for the tight technical greasy stuff we ride.

A few stalls, picking the bike up a few times in the heat and humidity here and your gassed for the day.

 

Kauai just had their anual hare and hound and from the reports I heard first place  A class finished in 6 hours...with only a few A-riders finishing.

The last few that did manage to finish did it 10 to 12 hours comimg in after dark.....I heard it was beyond brutal...as usual!!!

Guys were laying in the river botton pools trying to cool off enough to just ride out.

I stay away from that race just because.

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