Exhaust Header Question?

[Tom H Ca]

'73 R75/5. Do the exhaust headers need to be fully seated in the head for the header nut and rings to seal them? Or can they be 15mm or so short of fully seated and still seal with no exhaust leak??

I needs to know .
Tom

[Rob Frankham]

In principle, the seal is made by the compression rings which are at the edge of the spigot on the head so, as long as the header actually goes into the head, it will seal... but... there are a couple of very good reasons why the header should be fully seated...

1) The change in diameter in the head followed by the second change at the start of the header will disturb the gas flow. A slight effect but not for the better.

2) The header is partly supported by the physical fitting into the head. If it isn't fully home, then the pipe can rock at the joint which will eventually cause leaks, potential fracturing of the pipe itself and even the head casting. 15mm is a long way from fully home.

I would not want to fit it like that...

Rob

[Tom H Ca]

So it could work, but it's best to not do it. BTW: 15mm was just a guess, need to work on it some more.

I bought a set of headers on flea bay that are not bent exactly right where the muffler slides on. The angle looks right, but where they started the bend for the muffler I think is too far back. With the header fully seated in the head and the header clamp under the foot peg attached (which all looks fine), I can not slide the muffler on as it hits the foot brake lever.

I am going to look closer today and see what the exact issue it.

Thank you,
Tom

[Tom H Ca]

Well it turns out that the bend is not correct where it sweeps up for the mufflers. Stock header was bent at 20 deg and the flea bay were at 15 deg. That is why I could not get the RH muffler on, it would hit the brake arm when I tried.

I'm going to see if a muffler shop can correct the bend in the next week or so.

Tom