Pipes too big by 1mm.

André Bourbonnais · Apr 17, 2018

Hey everyone. Just bought new silencers and pipes and the pipe ends are 1mm to large in diameter. Anyone else encounter this? Should I just sand away till they fit?

chaztuna · Apr 17, 2018

André Bourbonnais said:
Hey everyone. Just bought new silencers and pipes and the pipe ends are 1mm to large in diameter. Anyone else encounter this? Should I just sand away till they fit?

I would not suggest doing that. What is the OD of the pipes? What is the ID of the silencer [muffler]?

Charlie

André Bourbonnais · Apr 17, 2018

Original is 73mm and new one is 74mm.

850commando · Apr 17, 2018

Andre; did you purchase both from the same source? in any case please post the od of the pipe and id of the mufflers. i have a similar situation where the mufflers are not supplied to fit over the pipe discharge.

André Bourbonnais · Apr 17, 2018

850commando said:
Andre; did you purchase both from the same source? in any case please post the od of the pipe and id of the mufflers. i have a similar situation where the mufflers are not supplied to fit over the pipe discharge.

Bought them both from the same place. Mufflers fit fine, it's at the head exhaust that it won't fit past the threads.

L.A.B. · Apr 17, 2018

André Bourbonnais said:
Original is 73mm and new one is 74mm.

That's almost 3 inches.
Do you mean 43mm and 44mm?

kommando · Apr 17, 2018

NOC has a thread on this exact issue with the flange oversize so it's won't enter the head, supplied by Norvil who will swear blind it's correct and your head is wrong 'You must have had the thread repaired and now it's too small'. Get out the file and never buy from Norvil again.

Fast Eddie · Apr 17, 2018

André Bourbonnais said:
Bought them both from the same place. Mufflers fit fine, it's at the head exhaust that it won't fit past the threads.

In that case, so long as you’re happy with the rest of the fit and quality, I’d just file them down.

Always good to let the supplier know about such things though.

850commando · Apr 17, 2018

okay so its not the exhaust pipe fitup to the muffler which is causing a problem. can you fill in some more info?

750 or 850 commando, single exhaust or balanced system, seperate system with crush washer or 75 system with spherical swivel?

have you tried to fit the exhaust pipe without using the exhaust nut or collet? a picture might help

sometimes a new one piece collet might not go into the exhaust port thread. i massaged the collet (break it and grind the end till it will allow the pipe to slip in and the threads to engage)...

André Bourbonnais · Apr 17, 2018

L.A.B. said:
That's almost 3 inches.
Do you mean 43mm and 44mm?

Oups. Yes

André Bourbonnais · Apr 17, 2018

850commando said:
okay so its not the exhaust pipe fitup to the muffler which is causing a problem. can you fill in some more info?

750 or 850 commando, single exhaust or balanced system, seperate system with crush washer or 75 system with spherical swivel?

have you tried to fit the exhaust pipe without using the exhaust nut or collet? a picture might help

sometimes a new one piece collet might not go into the exhaust port thread. i massaged the collet (break it and grind the end till it will allow the pipe to slip in and the threads to engage)...

Yup. So its 1mm too big and it wont go past the threads. Even with the exhaust lock nut off it still wont go.

850commando · Apr 17, 2018

is the collet still in one piece? then break it ,grind the ends at the break till flush then gentle grind the outside dia at the ends, shown in red, i think the collets as supplied are slightly wider at the ends and where they are joined , hence you cannot get them inside the thread.

hopefully someone will respond with a possible better solution...

André Bourbonnais · Apr 17, 2018

850commando said:
is the collet still in one piece? then break it ,grind the ends at the break till flush then gentle grind the outside dia at the ends, shown in red, i think the collets as supplied are slightly wider at the ends and where they are joined , hence you cannot get them inside the thread.

hopefully someone will respond with a possible better solution...

I'm talking about the actual pipe itself. The pipe that fits in the exhaust port and gets tightened by the lock thread. The circonference of it is 1mm off.

L.A.B. · Apr 17, 2018

850commando said:
is the collet still in one piece? then break it ,grind the ends at the break till flush then gentle grind the outside dia at the ends, shown in red, i think the collets as supplied are slightly wider at the ends and where they are joined , hence you cannot get them inside the thread.

There are no collets on '750' (unbalanced) pipes (it's a '72 750).
https://andover-norton.co.uk/en/shop-drawing/46/exhausts-mufflers-mute-passenger-footpegs

Collets are required for the balanced pipe exhaust rings as they have to fit over the flange because the balance stubs prevent the exhaust rings being slid up from the silencer end.

candyapplered · Apr 17, 2018

I had the same problem with exhausts from another supplier (not Norvil). I went round the circumference with a dremel like tool very gently, grinding a small amount off and it worked perfectly.

Bob Z. · Apr 17, 2018

As a side question, does an exhaust port thread repair reduce the inside diameter of the port?

André Bourbonnais · Apr 17, 2018

candyapplered said:
I had the same problem with exhausts from another supplier (not Norvil). I went round the circumference with a dremel like tool very gently, grinding a small amount off and it worked perfectly.

Smart

candyapplered · Apr 17, 2018

Bob Z. said:
As a side question, does an exhaust port thread repair reduce the inside diameter of the port?

I nearly went down that thought process when my flanges wouldn’t go in. I’m pretty certain my threads are not original. Then realised that the original exhaust lock rings still fitted.

candyapplered · Apr 17, 2018

André Bourbonnais said:
Smart

Thanks, wish I could take the credit, but it was my brothers idea. He’s always been more practical than me !

NortonMKIIA850 · Apr 17, 2018

kommando said:
NOC has a thread on this exact issue with the flange oversize so it's won't enter the head, supplied by Norvil who will swear blind it's correct and your head is wrong 'You must have had the thread repaired and now it's too small'. Get out the file and never buy from Norvil again.

+1 on that, that was my experience. A few minutes' filing will show you that it's easy to make these pipes fit, and that you must never buy from Norvil ever again, if you can possibly avoid it.

Pipes too big by 1mm.

André Bourbonnais

chaztuna

André Bourbonnais

850commando

André Bourbonnais

L.A.B.

Moderator

kommando

Fast Eddie

850commando

André Bourbonnais

André Bourbonnais

850commando

André Bourbonnais

L.A.B.

Moderator

candyapplered

Bob Z.

André Bourbonnais

candyapplered

candyapplered

NortonMKIIA850

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