FMF Powerbomb

[Kram Nella]

Ok, so I got a fmf power bomb header from ebay and the ad said for 01-06 YZ250/WR250's. When I compare the power bomb and the stock header I notice the power bomb has a larger circumference exit pipe (where it attaches to the midpipe / silencer) than the stock header. So my midpipe gaskets' ID is smaller than power bombs' OD. Also the power bomb is about 3/4 inch longer. The bag that the power bomb came in said YZ250. Did they send me the wrong header? Is there a thinner gasket that will let me use my stock silencer w/GYTR tip?

here's the ad:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200318568600

What do you think? How do I remedy my dilemma?

[KJ790]

I believe if you use the midpipe gasket out of an 06 YZ250F it will work. They didn't make it to fit the stock silencer, it was made to fit FMF silencers, which are the same diameter as the 06-09 headers at the midpipe. The bend changed slightly for 07-09, but you can still get those pipes to fit fine (should the one they sent be for an 07-09 instead, but I doubt it is). It should have a part number on it, you can always match it up on their website to be sure.

[Toby_S]

The gasket out of a 426 (probably 400 and 450 too) works. It has the same header OD as a power bomb. I put one on my '02 and it was perfect. Check the dimension when you get it though, just to make sure I remember right. I have put an earlier post up about this. You might look for it.

The models above probably work too, because they stepped the header in those models (I think). You can compare part numbers on the Yamaha of Troy website.

I confirmed it: Here's the link. https://www.thumpertalk.com/forum/showthread.php?t=498580&highlight=

I am also currently running a Powerbomb in a White Bros. E2 muffler. It turns out that a copper fitting for a 1 1/2" pipe works perfectly for that. I slit it half way from both ends with staggered slits so that it could compress, and it works fine and doesn't leak.

-Toby

[BazookaJoe]

The older Powerbombs have a larger exit diameter than a stock 01-05 YZF or 01-06 (and maybe newer?) WRF muffler inlet diameter. If Toby's info is correct, you're in business, otherwise, you may need to run the PB with a FMF pipe.

[KJ790]

The gasket out of a 426 (probably 400 and 450 too) works. It has the same header OD as a power bomb. I put one on my '02 and it was perfect. Check the dimension when you get it though, just to make sure I remember right. I have put an earlier post up about this. You might look for it.

The models above probably work too, because they stepped the header in those models (I think). You can compare part numbers on the Yamaha of Troy website.

I confirmed it: Here's the link. https://www.thumpertalk.com/forum/showthread.php?t=498580&highlight=

I am also currently running a Powerbomb in a White Bros. E2 muffler. It turns out that a copper fitting for a 1 1/2" pipe works perfectly for that. I slit it half way from both ends with staggered slits so that it could compress, and it works fine and doesn't leak.

-Toby

Only the gasket for up to an 06 YZ450F would work, after that Yamaha increased the size of the pipe. The 06-09 YZ250F uses the same gasket at the 03-06 YZ450F.

[Kram Nella]

Great to know I can still use my stock silencer. I orderer the gasket from the 06 YZ250F from TT. This should work. Many thanks to all!

Mark

[Kram Nella]

Oh yeah, two other things. What about the length difference? Do I slide the PB header into the midpipe further, or do I need to cut it off? The header doesn't look as if it will go past the swelled part of the midpipe.

And how in the h@#$ do you torque to specs the bolt and nut at the head? There isn't enough room to fit the torque wrench between the header and the nut, and between the bolt and frame.

I removed the stock header before I realized the size differece of the two headers. I cut the end off a 6mm allen and inserted it into a 6mm socket to remove the bolt, and used a wrench to remove the nut. When I put the stock header back on (it's going to be a few days / week before the new gasket arrives and want to ride tomorrow) I stated the nut on the stud, and put the bolt in the other side. When I went to torque the the bolt it seemed like i used a lot of force before the torque wrench clicked. Did the long 6mm allen change / increase the torque even though the wrench was set to 17 ft/lbs? The header flange looks bent now.? Then tightend the nut with a wrench to what I thought was 11 ft/lbs.

[KJ790]

Oh yeah, two other things. What about the length difference? Do I slide the PB header into the midpipe further, or do I need to cut it off? The header doesn't look as if it will go past the swelled part of the midpipe.

And how in the h@#$ do you torque to specs the bolt and nut at the head? There isn't enough room to fit the torque wrench between the header and the nut, and between the bolt and frame.

I removed the stock header before I realized the size differece of the two headers. I cut the end off a 6mm allen and inserted it into a 6mm socket to remove the bolt, and used a wrench to remove the nut. When I put the stock header back on (it's going to be a few days / week before the new gasket arrives and want to ride tomorrow) I stated the nut on the stud, and put the bolt in the other side. When I went to torque the the bolt it seemed like i used a lot of force before the torque wrench clicked. Did the long 6mm allen change / increase the torque even though the wrench was set to 17 ft/lbs? The header flange looks bent now.? Then tightend the nut with a wrench to what I thought was 11 ft/lbs.

Most people don't use a torque wrench on the nuts that hold the header on, as it isn't crucial to be right. Just make sure you go tight enough that it won't come loose, but not so tight that you bend the flange. If the powerbomb is held on by springs (like most are) then you can put the flange and outer collar on first with a torque wrench, then slide the pipe in and put the springs on.

As for the length difference, are you sure you got all of the mounting hardware? If it is held on with springs then there should be two collars, a flange, and two springs with it. These may make up the difference in length between the two pipes.