FMF Mega Bomb = fittment problems

Was all excited to finally get my FMF Megabomb in the post today, but this soon turned to dismay to find that it doesn't even go close to fitting....

The 2 main problems i have are that the outlet size from the M/B to where it mates to the muffler is way, way, too big. It's like a cock in a sock - just flops around big time. I thought that this problem itself may be overcome with a sleeve as such, and i have read on other posts here that this may be the case depending on what type of rear muffler is being used. ( My case i have the GYTR rear pipe ).
( I'll have to look at my original rear pipe set up to see if that would have been a "better" size to match up. Only problem is that i can't even check that right away as the original pipe is in a remote storage shed, so unable to check until the weekend ).

The other fittment concern is that the 2 hole mounting flange where the header bolts onto the exhaust port does not slide over the 2 studs, due to the placement of the holes in the FMF flange plate - they are not drilled out quite "wide" enough. Again, whilst this alone "could" be rectified by further elongating the holes, i feel that this may point towards it just being the wrong part to start with, or maybe it's from a "bad" batch so to speak.

One other noticable difference is that the internal diameter of the exhaust port end of the FMF header pipe is noticably smaller than the original internal pipe diameter ?. It would seem a bit strange for this to be such a difference to go smaller at this end of the header ?.

Anyway i will make contact with the USA supplier soon to give them the full run down & see what they have to say, but i thought i'd just ask here first to make sure that iv'e covered all of the "basic's"..... I know that plenty of you guys on here have fitted this header, so i'd have thought that if there were any major fitting problems then it would proberly be mentioned here. ( But as i've just mentioned above, all i can find in a search here is about the possibility of the "adaptor" sleeve at the outlet end ).


Lastly the header seems to have come in the original FMF box, which has a "barcode" part number sticker on the box - it lists as below.


" FMF   YAM WR250R/X '08-13 S/S MEGABOMB HEADER"   ( So by this description alone it "should' be correct ).


On this same barcode sticker is a short number below the barcodes, the number is listed as " 044356"  


There is also a date code & patent number on the FMF pipe as well, it's on the "spot welded FMF plate". ( I don't believe this is a relevent ID number as such ?? . But i will list it here if anyone thinks that it may be a relevent cross reference number ).


Anyway i'm hoping that some of you guys on here with the FMF M/B can give some feedback & maybe shed some further light on this.

Would be perfect if anyone with the same set up as me can post please. ( FMF MegaBomb with GYTR rear pipe ).


Cheers guys.

Sounds like you need the "coupling spacer" thingy to mate the FmF header to the GYTR pipe. 

click me  <-- see my melted spacer here 

The FmF ID/OD of header pipe is larger than the stock ID/OD. 

So if your GYTR muffler was a direct replacement to the stock muffler, and did not require a coupling spacer, yeah - you'll not be able to mate to the FmF header. 

As for the holes in the flange plate - I can't answer that.

Thanks for the above reply Moto...


Anyway after some more "searching", i ended up finding this thread as per below right here in our very own "back yard". ( Had not seen this thread here on our forum in my previous site search, for some reason unless i actually type in "FMF PB Header" as the minimum words on the search function it won't come up ? - I actually stumbled on to it during lots of "FMF WR250R" google searching ).


In any case it seems to relate directly to my concern, and it also points to the fact that the o2 sensor equipped bikes have a different diameter GYTR rear pipe. ( See 'ol mate OP below is from NZ ).


As i've mentioned i'm not really too surprised or alarmed about the header to rear pipe issue, i will just look at the required "adaptor" sleeve.....but the main concern was for the exhaust port flange plate that doesn't quite fit over the studs. Anyway it seems all else is "correct", so maybe i have just been a bit "unlucky" with a slight production defect. I will just use a small die grider bit to slightly elongate the holes as needed. 


Anyway thought i'd just add the below "thread link" to my own posting as it may help others out in the future as well. I will look at doing the required mods over the next few weeks as i get the "free" time, and then report back here with my results just to round out this thread.


[url=https://wr250rforum.forumotion.com/t1179-fmf-pb-header-wrong-fit?highlight=FMF PB Header]https://wr250rforum.forumotion.com/t1179-fmf-pb-header-wrong-fit?highlight=FMF%20PB%20Header[/url]



Cheers guys.