450 Plastic on 426 COMPLETE WITH PICS


215 replies to this topic
  • Speedracer747-400

Posted January 31, 2010 - 03:32 AM


I plan on doing this conversion on my 02 YZ426F. I'm planning on buying new exhaust anyway, most likely FMF Q4 muffler and Powerbomb header. Would it be better to buy the muffler and header for a YZ450F? Less likely to have clearance issues with the subframe and rear shock?

Will the conversion work with an aftermarket desert tank? Most likely getting a YZ450F Acerbis tank.

  • myoung

Posted January 31, 2010 - 07:33 PM


I plan on doing this conversion on my 02 YZ426F. I'm planning on buying new exhaust anyway, most likely FMF Q4 muffler and Powerbomb header. Would it be better to buy the muffler and header for a YZ450F? Less likely to have clearance issues with the subframe and rear shock?

Will the conversion work with an aftermarket desert tank? Most likely getting a YZ450F Acerbis tank.


I would say get the header for the 426, but there are guys running a 450 slip on and say it bolts up fine, maybe go that route. I'm running the Q2 and Powerbomb for a 426 with a 1" drop bracket I made and have no clearance issues. I've read that some guys were able to get a 426 slip on to line up with the 450 subframe, but I wasn't able to.

I would think the 450 desert tank should work, but it's hard to be 100% certain. There are different size desert tanks and the biggest ones might run into something a smaller one wouldn't, but I don't know for sure.

Edited by myoung, January 31, 2010 - 09:05 PM.


  • moto2000

Posted January 31, 2010 - 08:39 PM


One thing to be aware of with a larger tank is the oil fill on the frame backbone.

I use an IMS 3+ gal tank and had to heat it slightly in the front to get it to form around the oil fill. Otherwise, it sat too far back and the seat wouldn't line up. Not a big deal....sounds worse than it is.

Not sure about clearance with an Acerbis tank though....they seem to carry more fuel up high in that area vs the IMS which carries the fuel lower on the sides.

I run a 426 FMF Powerbomb and Q2 with no issues. Silencers like the Q2 are nice because they have the moveable mounting strap instead of a fixed mount...I've also used a full 450 system (FMF) with no major issues, but the headpipe bend seemed a tad off when mounting to the silencer.

Maybe the best setup would be a 426 header and a 450 silencer?

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  • myoung

Posted January 31, 2010 - 09:10 PM


One thing to be aware of with a larger tank is the oil fill on the frame backbone.

I use an IMS 3+ gal tank and had to heat it slightly in the front to get it to form around the oil fill. Otherwise, it sat too far back and the seat wouldn't line up. Not a big deal....sounds worse than it is.

Not sure about clearance with an Acerbis tank though....they seem to carry more fuel up high in that area vs the IMS which carries the fuel lower on the sides.

I run a 426 FMF Powerbomb and Q2 with no issues. Silencers like the Q2 are nice because they have the moveable mounting strap instead of a fixed mount...I've also used a full 450 system (FMF) with no major issues, but the headpipe bend seemed a tad off when mounting to the silencer.

Maybe the best setup would be a 426 header and a 450 silencer?

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Good catch on the tank, I didn't think about the oil fill.

You made me think, I got my post wrong. I had Q4 on the brain, I'm actually running a Q2 as well. But I think you're right, a 426 header and 450 pipe would be the best set-up. I think in the beginning of this we all thought the 450 pipe wouldn't work. Turns out it does, but the 450 header will be off a bit.

  • myoung

Posted December 12, 2010 - 10:06 PM


Sorry I didn't see this sooner. I know it's a bit late, but maybe some one else can use the info.

Here is the template........

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Easiest way to lay this out is to locate the top two holes at the 3 15/16", then use a compass to locate the other two holes with the two measurements that will cross each other and give you their position.

Here is the pieces..........

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Here it is mounted.........

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I had to update my Photobucket account, here's the pics again with the updated links.


The template.......

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The pieces........

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Assembled........

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  • mx250s4life

Posted December 14, 2010 - 04:02 PM


is there a kit or way to do this for a 01 yz250f?

  • grayracer513

Posted December 14, 2010 - 04:08 PM


No, there's no kit.

  • myoung

Posted December 14, 2010 - 05:18 PM


is there a kit or way to do this for a 01 yz250f?



There's no kit, but an '01 250F for the purposes of this swap would be the same as a 400/426. The parts needed and the fab work described in this thread is the same for your bike. :thumbsup:

  • mx250s4life

Posted February 08, 2011 - 12:33 AM


There's no kit, but an '01 250F for the purposes of this swap would be the same as a 400/426. The parts needed and the fab work described in this thread is the same for your bike. :thumbsup:


sorry if this is a bit late but i have read this entire thread before and was a little skeptical but now my dad wants to convert our 2001 yz250f. unfortunatly i need help making the list of parts from what bike along with years that are needed and any cutting or trimming needed, like for the subframe. i got the specs for the tank mount. however, i'm not clear as to what happens to the oil reserve for the rear brake right side of the bike. where on the bike does it get moved to or does the newer master cyclinder eliminate the need for it? mine is being held on with zip ties atm. if anyone could help me figure out the specs and parts list i would be eternily grateful.

  • myoung

Posted February 08, 2011 - 01:09 AM


I'll dig this from my memory instead of going through the whole thread again.

Parts are from '03 to '05, 450 or 250 YZ. The list of parts needed is in the beginning of this thread.

Modifications are fairly simple, you need to make some brackets for the tank, and you need to either narrow the frame or widen the subframe on the right side of the top mount location, I think it was like 5 or 8 mm's or something. On mine, I cut the subframe instead of the frame in case the bike was ever put back to stock. Also, I've posted the drawing I made for my tank brackets which are fairly easy to make.

The late model rear master cylinder would solve your remote reservoir problem, it doesn't have one. Otherwise you'd have to fashion some kind of mount. After that, it's all a bolt on operation.

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  • grayracer513

Posted February 08, 2011 - 09:01 AM


The info on parts is in the thread. If you buy new, it will cost you a fortune. The parts you want are from the '03-'05 model years.

  • umu24013

Posted April 01, 2011 - 08:59 AM


Here's another version of the tank bracket made of 14 Ga. aluminium:

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  • myoung

Posted April 02, 2011 - 10:28 AM


Here's another version of the tank bracket made of 14 Ga. aluminium:

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Looks good! :cheers:

I was looking at doing mine similar, but I decided I didn't want to use the engine mount. This is good so people can see a couple options. Nice work!

  • jb034

Posted August 05, 2011 - 07:14 PM


Can i put a newer number plate on my 1999 yz400f?

  • myoung

Posted August 05, 2011 - 08:03 PM


Can i put a newer number plate on my 1999 yz400f?



If my memory serves me correctly, the triple clamps are different where the plate mounts. I think the top clamp uses a screw through the front of the plate on 98-99 where 00-on uses a screw behind the plate into the top of the top clamp. I think the locating pins/holes on the bottom clamp are the same.

  • jb034

Posted August 06, 2011 - 07:01 AM


If my memory serves me correctly, the triple clamps are different where the plate mounts. I think the top clamp uses a screw through the front of the plate on 98-99 where 00-on uses a screw behind the plate into the top of the top clamp. I think the locating pins/holes on the bottom clamp are the same.


Yea id say thats correct, you think theres any way to put a hole in a newer plate and mount it up like the 99 style? id be putting a number decal on it anyways so you wouldnt see the hole

  • Parx_400

Posted September 12, 2012 - 11:58 AM


Has anyone done this using a 6.6 gal tank? I have owned both a wr450 and wr400 in the past. I'm thinking of getting a 2002 426 CA plated but the only thing holding me back is the gas tank sizes. I had the 6.6 on my wr450 and really want that size. I don't see why it would not work and I have a buddy who will help me fab up the lower and upper tank brakets.

  • Parx_400

Posted September 12, 2012 - 12:55 PM


Looks like I found one.

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  • Blodhgarm

Posted December 24, 2012 - 10:56 PM


Is there a way you can get just the 450 side panels and airbox?

  • gstewtec

Posted January 10, 2013 - 05:50 PM


This is my conversion.

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