Difference between Gen I and Gen II stock header

[UselessPickles]

Just an FYI. I know that a couple people have confirmed that the exhaust header is physically interchangeable between Gen I and Gen II FJRs, but I wanted some more details about why they were different part numbers before I bought a header from a 2005 for my 2008. I contacted Yamaha "customer relations", and after a day of waiting they called back with more information than the obvious "they are different part numbers, so we can't guarantee compatibility".

They say that for 2006+, the collector (the big fat chamber) received some catalytic converter material in addition to the catalytic converters that already reside in the two exit pipes from the big collector. So it looks like the only possible side-effect of using an old header on the newer bike would be less restricted airflow (and more emissions).

 

[Constant Mesh]

The oxygen sensor mounted in the exhaust assembly also changed. The '06 sensor includes an internal heater which the earlier models didn't have.

Maybe the sensors are mechanically interchangable too -- same thread diameter and pitch.

 

[UselessPickles]

Yes, the O2 sensor bung (gotta love the opportunity to use that word correctly!) is the same on the Gen I and Gen II headers. But that's a good point - you can swap the headers, but keep the O2 sensor for your bike's year. In my case, it doesn't matter because I have an aftermarket wide band O2 sensor paired up with a self-tuning fuel system.

 

[FJR919]

Pickles, I'm using an '05 on my '08. I put them side by side and I can't see any difference. I wanted to use the gutted cat header from my '05 on the '08. I never could get an explanation for the different part number.