Author Topic: FMF Fatty YZ 490 not the same as WR 500 FMF Fatty :(  (Read 757 times)

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Offline vader-nator

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FMF Fatty YZ 490 not the same as WR 500 FMF Fatty :(
« on: November 14, 2017, 04:28:43 PM »
I was doing a strip down clean up of my newly purchased WR 500 when I discovered that the good FMF fatty pipe it has on it may be shiny but its been hit. It has a crack in the weld along the bottom bend near the lower frame mount and its way off true at the manifold. Blowing goo all over the place.

After all the banter about the YZ 490 FMF fatty being an easy fit for the WR 500 I grabbed one...........BUT  I was surprised that there is a little more to it than just bolting one on.

We all know the WR 500 has a lower frame bolt mount at the outside left of the pipe and the YZ 490 just has springs to mount the pipe. This is potentially an intersting thing. I have 2 pipes for the bike and both have stress cracks along the welds of that bottom section of the pipe near the frame mount. I ask - Is that WR 500 frame mount a blessing or a curse? My owners manual doesnt even depict the lower frame bolt at all for the 1992. Perhaps its better off with just 490 springs.


Next problem

The stinger is straight and way longer on the brand new YZ 490 pipe I just bought and doesnt have a bend before the air box. Then it has no bend for fitment to the WR gen muffler and is pointing straight back when it needs to be turned about 30 degrees.

I am no pipe doctor but I am a problem solver.

I am going to cut the extra 2 inches off the end of the 490 pipe and then make a v cut and bend the tip to fit the muffler. No way in hell I can weld it but without making it into swiss cheese.

Then it will be a matter of getting radiator hose to fit snugly over the pipe joins and to fit over the v cut I make.

Any warning tips before I get the grinder out would be much appreciated. But as it is, the YZ 490 pipe will melt the airbox and will be over 2 inches too long to go to muffler..... and wrong angle.

Thanks guys

Rob


Offline Jamie70

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Re: FMF Fatty YZ 490 not the same as WR 500 FMF Fatty :(
« Reply #1 on: November 14, 2017, 09:02:43 PM »
I’d be tempted to find a good welding/fabrication shop that does TIG welding and get them to do it the way you need. Get them to modify the YZ pipe using the WR pipe as a guide (knowing that it’s out of whack further down).

Offline 4V5

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Re: FMF Fatty YZ 490 not the same as WR 500 FMF Fatty :(
« Reply #2 on: November 15, 2017, 12:21:52 AM »
have it welded.. make the join to the muffler the same setup as the factory and use a propper joint.. same amount of work for a much tidier result.

IT465x4 IT400C IT175F YZ465G YZ250C YZ250WR XJ650G RD350LC RD250LCx5 DT175Nx3 TW200x2 DT200L DT200R RT3 RX100G GT80F YZ80L PW50J KH250B1 KZ250D1 PE175C TS250ER TS185ER AG175B AG100

Offline vader-nator

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Re: FMF Fatty YZ 490 not the same as WR 500 FMF Fatty :(
« Reply #3 on: November 18, 2017, 10:09:37 AM »
Thanks guys.

I guess I just need to be patient about it.

One thing my younger self never had when I owned my last wr 500.

Better to do it great once  than do it twice :)

Will tell you how I go :)


Offline vader-nator

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Re: FMF Fatty YZ 490 not the same as WR 500 FMF Fatty :(
« Reply #4 on: December 10, 2017, 10:09:52 PM »
I did cut the pipe myself and made a nice joiner for it out of car radiator hose.

I guess the need to tinker in the shed got the better of me.

All is well that ends well. The pipe angle before the muffler was good as it just missed the air box and all I had to do was install it.

Easy fix that became a mammoth task because I spent too much time pondering and not enough time doing.

A YZ 490 pipe will fit. It just needs a bit of trimming off the end :)