silencer repair/refurbish

[billywingnut]

My bike is fitted with an original exhaust system the chrome is very good. However I have noticed a small hole underneath water comes out during idling. Does anybody know if there are any companies out there  that can refurbish these silencers as they are as rare as rocking horse droppings.
When I removed it to check it out  a handful of rust came out which is a shame as it's pretty solid and  sounds good not loud.

[Johnwebley]

I think the four pipes all have drainage holes.

What bike is it?

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[Nurse Julie]

If its your 400/4 pipes, they don't have a drain hole in them, so its not a standard hole. It's a shame when these old pipes rot from inside out, you don't know anything about it until it happens unfortunately. Is it the silencer that the hole has developed in or the collector box.

[billywingnut]

The hole is in the silencer a couple of inches from where it enters the splitter box, there doesn't appear to be any blowing from it when engine is running.

[Nurse Julie]

The hole is in the silencer a couple of inches from where it enters the splitter box, there doesn't appear to be any blowing from it when engine is running.

Maybe the baffle is welded at that point stopping anything blowing out of the hole 🤔 I suppose it's something us 400/4 owners will all face at some stage. I gave my silencer, a Brituro, a good shake about 4 years ago and no rust came out then and I do tend to run my bikes very slightly on the rich side which helps with a bit of rust prevention. What do you plan doing with it?

[TrickyMicky]

I have an original exhaust on my 400, and the hole just behind the clamp is meant to be there, the idea is that any nasty fluid can drain out. Regarding its effectiveness, well that's another story! Maybe I'm fortunate that it is kept in a dry garage, but even so I've always tried to work on the practice that the engine only ever gets fired up if it's going to have a long enough run to get hot and everything is nice and dry by the time I get back home. Many, many years ago with my first CB750 I used it for work every day which involved a 4 mile journey each way, believe me, replacement exhausts were bloody expensive even then!

[billywingnut]

Thanks for your comments, I will continue to run with it until a suitable new replacement can be found.

[K2-K6]

They rust inside as most pipes are just bare steel.

Normally the most aggressive component in exhaust gasses has effectively been sulphuric acid resulting from the sulphur content of fuel going through the combustion process. The more unburnt fuel from (rich)  inefficient burn,  the more sulphuric affected liquid is present in the output. Most of the original fit had small holes to avoid this pooling at the lowest point of the system,  but short runs are always going to be an enemy.

With the cost of original type pipes for restoration etc being so high,  it could be worth thinking about jetting level as part of their preservation.

It's almost disappeared from cars nowadays.  Lowered sulphur in fuel and running them with mixture adjustment loop to avoid overfuelling has made exhaust last much longer on petrol cars as compared to fairly regular replacement some years ago.

[Johnwebley]

Go for a ride. If you can touch the exhaust. It's not hot enough.



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