FMF PB Header, wrong fit ?

Hi all . . I recently bought an FMF PowerBomb for the WR from the TT shop. On going to install it I find that, whereas the stock header is a snug/slip fit INSIDE the stock muffler front pipe, the FMF is much larger & slips OVER the muffler front pipe .. . but, it's a VERY loose fit that isnt going to seal.

Looks like it is either the wrong header, or there needs to be a cylindrical gasket to close the gap . .. . but in that case the header would need to be split & clamped down onto the gasket. . . .

So, chances are good that it's the wrong header . .. .

I'm awaiting a response from the TT Shop, but I'ld like to be armed with some independant feedback if possible, so would anybuddy care to comment from having already installed one of these (succesfully!) .. . . . .

Thanks guys.


BrooC DownUnder

FWIW the stock header pipe end (which slips INSIDE the muffler front pipe) is 38.5mm OD, whereas the new FMF header pipe end measures 42mm ID.

Why on earth would you replace the header pipe yet keep the stock muffler?????

Is that what you are trying to do?

The Powerbomb won't fit the stock pipe. If you buy a FMF pipe it comes with an adapter to fit the stock header, but you can't put a FMF header on a stock pipe. I agree with Motokid, why buy a header and keep the stock pipe? Why not get a full system?

Probably worried about noise.

I'd get the FMF Q4 muffler to go along with the header you just got.
Perfect fit, you get more gnads, you lose the silly cat inside the stock muffler as well as some weight, and although it is louder, it's not too loud. :)

Quote :

The Powerbomb won't fit the stock pipe.

I had one on my WRR for several weeks before I went back to the stock header with a bung for a PC V / AT setup. You don't use the wire/fiberglass gasket, just slips into the stock mid pipe. It IS a tight fit. I had the stock muffler and the GYTR muffler each mounted with the stock header and the FMF Power Bomb. All 4 combo's worked.

I found it easier to leave the stock muffler mounted on the bike and slide the FMF in as you also seat it in the exhaust port. You have better leverage and control than doing it the other way.

The FMF header does not fit OVER the stock mid pipe.

I'm surprised it fit so well. I didn't think the Powerbomb would work with the stock pipe. Also, just about every exhaust system I have ever seen has the forward most pipe mate INSIDE the one to the rear of it as you go back to the tailpipe outlet. In other words, you want the pipes to be inside the one to the rear for better sealing, no matter how well the fit. Just seems logical to have the pipe go inside the one to the rear since it makes it harder for the exhaust gases to travel back forward to get out of the joint. If you have the forward pipe OUTSIDE the rear pipe, you better have a good seal and clamp as you stand a better chance of gases escaping from the outer pipe of that joint just from the shear direction of the flow and pressure. Does that make sense?

Quote :

Also, just about every exhaust system I have ever seen has the forward most pipe mate INSIDE the one to the rear of it as you go back to the tailpipe outlet.

The last sentence in my post:
The FMF header does not fit OVER the stock mid pipe.

The second sentence of my post:
You don't use the wire/fiberglass gasket, just slips into the stock mid pipe.

ramz wrote:

Quote :

Also, just about every exhaust system I have ever seen has the forward most pipe mate INSIDE the one to the rear of it as you go back to the tailpipe outlet.

The last sentence in my post:
The FMF header does not fit OVER the stock mid pipe.

The second sentence of my post:
You don't use the wire/fiberglass gasket, just slips into the stock mid pipe.

My bad. Guess I should clean my glasses more often. I was going by what the OP said that his PB fit OVER the muffler pipe.

Nah...not enuf beer there, sweetie.

This is straight from the FMF website:

Our
headers, whether it be the PowerBomb or the MegaBomb, are fitted to
match an FMF series muffler. We do not recommend or guarantee you try
to match it to a stock muffler.

So if it fits, it's luck & still might not be the best idea.

SheWolf wrote:

Nah...not enuf beer there, sweetie.

Cut me some slack Wolfie. It's only 10 am here. I just finished my coffee. Beer-thirty isn't for another hour or so.

Hey it's October...Oktoberfest! But yeah...that header is made to go with the FMF pipe. I wouldn't be trying to screw with it otherwise.

Thanks all . .. I guess I should have had a lawyer review my post for 'errors & omisions' prior to sumission huh! ;-]]

OK, the bike presently has a GYTR muffler . . . I was comparing the FMF PB to both stock & GYTR muffpipes in trying to make sense of what to do for a fit .. .

First ~ I can see how the PB would slip inside the stock front pipe with gasket omitted, but obviously I wouldnt bother running a PB with a stock muffler.

Next, the frontpipe of the GYTR is made to be a snug fit over the end of the stock header WITHOUT the gasket, ie it is approx the same 38.5mm ID as the OEM gasket.

Finally, the PB header is made to fit INSIDE the clamping joint of the stock muffs frontpipe WITHOUT the gasket, ie 44mm OD.

So, while the PB would mate with the stock muff, it is a NO-GO sloppy fit OVER the GYTR frontpipe.

I expect that FMF have done it this way to gain max pipe diameter as far as possible. Nevermind that it is made to fit a Q4 ~ those just arent available here without big airmail charges, but GYTR are available so that's what I got . . .


TT Shop are going to fwd my query along to FMF, but I expect that the response is going to be that the FMF product just aint compatible with the GYTR muffler.

It wont be worth postage back to the states from NZ even if they do offer a refund, so I guess I'll be looking to get my tame machinist pal to do some cutting & butting with the 'electrick glue'!

However, it might be worth posting somewhere that these parts are NOT all interchangeable . .. .

I'll come back later & post re any further developements or solutions.

Cheers
BrooC DownUnder

whooooooshhhh, answer back from TTShop "Thats the thing about FMF. They will not tell you if one header or another will fit with any other exhaust stock or aftermarket. They are crazy with that."

So, there ya go . .. . . now off to see my machinist/welder mate.

The 'learning point' here? DONT assume things are interchangeable, ask around first, mutter mutter .. . . .

Regards from the Blunderer DownUnder.
BrooC in NZ ;-]]

Here's a picture of the FMF Power Bomb header INSIDE the GYTR mid-pipe:



Here's a closeup:



Closer still:

That answer doesn't surprise me. The people at FMF couldn't find their butt with both hands on the map. Glad you got it figured out though. Post up some performance results when you get the PB mated to the GYTR. I think that would be a first. Interested to hear how it runs with that combo.

Oooh I think that wound got opened up there... At least you got your packing sorted out with those yahoos, Mark...

Well, I'm not so sure about the packing until I redo it next time to see how this stuff lasted. And I never got a reply from the President of FMF who I wrote a very long nastygram to. BUT, I do see where they have revamped their web site a bit to make it easier to pick the correct packing, so maybe I did get through to "somebody"!!

http://www.fmfracing.com/Mode/Category/47/

Notice how the Q-Pillow packing now says it is NOT for use with the Q4 muffler. It didn't say that before!!

Sorry for the thread hijack BTW. Didn't mean to get off topic.

That was my fault... Header connects to the tailpipe that needs to be repacked with fluff and stuff...preferably not mousie nesting material... Ok, enuf out of me.

.. . those pics from ramz sure muddy the waters coz NO way will my FMF-PB header fit INSIDE my GYTR pipe!

My GYTR pipe-end is 38mm ID & 40mm OD, whereas the PB hdr end is 42mm ID & 44mm OD.

Looks like there might be different series of these various products around, just to confuse things further . .. could be part of why FMF wont attempt to get into what will or wont fit what etc..

The fix for mine will be fairly simple, just a 1mm sleeve of 40mm ID belted onto the start of the GYTR pipe, & the FMF should sleeve snugly over it, with mebe some HT silicone sealant . . .if worst comes to worst I might have to slit the FMF to allow a clamp to pinch it down tight against any leakage.

I'll post again when its sorted.

Cheers from DownUnder

Maybe the "down under" version of the GYTR with the O2 sensor bung has a larger diameter pipe?

ramz wrote:

Closer still:

Hey ramz, is that a little K&N breather filter you have on that hose next to the airbox? Is that the hose to the valve cover or the AIS?

My machinist pal turned up an ali sleeve that does the trick nicely .. . . doesnt even need a clamp or sealant. . . . . . I'ld post a pic but so far I've not sussed how to use a hosting site .. . . . .there's always something new to be learned!

Cheers
BrooC DownUnder

. . . further to my previous re image hosting sites (like mebbe SmugMug?) does anybuddy have any special advice/clues/tips to pass along . .. something very simple would suit, & 'free' would be nice too .. ..

Thanks

BrooC DownUnder

If you're looking for an image hosting site, www.photobucket.com does it for me, and it's free. :)