Pro Circuit Pipe

[fbonneville]

Just a quick question. While changing my top end a few weeks ago, I forgot to put the washer that goes in between the pipe and the exhaust port. I rode a few times this way seemingly without a problem. Yesterday I went to replace my old plug (have been using same one for over 6 months) and noticed how the insulator had gone from thick black to a light gray.

Does anyone have an explanation for this? What's the purpose of this washer? Is it needed? Why did my plug start indicating I was running a good mixture...

All oddities.

 

[steve.emma]

i might be wrong but i think the washer is there to stop the steel pipe flange rubbing on the alloy cylinder head and causing the head to wear out of shape,as the pipe flexes or gets bumped and moves around.
also having a spacer such as a washer between the head and pipe changes the power band characteristics slightly and maybe this is why your bike runs better now.

 

[Moto Squid]

On my old kaw I had one of those spacers...if I remember correctly :confused: it helped slightly with low end power