The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Josh Cox on 17.04. 2010 10:47

Title: Exhaust pipe staining ?.
Post by: Josh Cox on 17.04. 2010 10:47
Evening Gents,

Have stainless pipes on my bike and it is suffering from exhaust staining, how do I stop this happening ?.

Have heard of:

* Painting the inside of the pipes with high temp paint,

* Putting copper wire in the pipe, guessing they were suggesting copper loops inside the pipes at the exhaust port end, guessing this would disturb the airflow ?.

What is the best way to remove stain, have heard of a nitric acid "pickling solution", has anybody used this ? (paint stripper, oven cleaner ?).

Look forward to some new ideas.
Title: Re: Exhaust pipe staining ?.
Post by: BSA_54A10 on 17.04. 2010 11:57
Stainless Steel sauce pan cleaner will work wonders.
It will leave the pipes quite dull ( etched ) so you will have to follow up with an abrasive polish like Autosol.
The discolouration is due to the heat in the pipe and is a natural and quite normal occurance.
If you take them off and polish them to a mirror shine this will reduce the surface area and reduce the tendency to colour.
Spraying the inside with a ceramic coating will reduce the temperature where the coating is but may cause mufflers to discolour.

Proper tuning will have the greatest affect on pipe colour.
Running larger exhaust valve gaps will also reduce the discolouration ( but sound like a bomb on 2 wheels).
Increasing the inlet overlap will also help but increase the fuel consumption and may also lead to detonations inside the muffler.
Bike Beesa
Title: Re: Exhaust pipe staining ?.
Post by: muskrat on 17.04. 2010 13:18
G'day Josh,
               I second Trevor's thoughts. You might be running a little lean on the mixture and/or the wall thickness of the headers is a bit thin. I've had ss pipes and mufflers on the '51 since '84 and show verry little discolouration. I think they were from Overlander for $320 back then.