The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Viking on 09.09. 2017 20:25

Title: leaky exhaust in SR head
Post by: Viking on 09.09. 2017 20:25
I have problems with leaky exhaust pipes in the SR alu. cylinder head.

The exhaust hole is bit larger then the pipe.
Used asbestos string to seal, but don' t last long.
Fitted exhaust putty, no luck.

What can be done with out removing the cyl.  head ?
Title: Re: leaky exhaust in SR head
Post by: Billybream on 09.09. 2017 20:52
PTFE tape might be worth a try
Title: Re: leaky exhaust in SR head
Post by: muskrat on 09.09. 2017 21:47
G'day Viking.
You could take it to a car exhaust pipe shop and get the pipe expanded a tad. Take the bike and drop the pipe off there so it can be checked for fit and adjusted.
Cheers
Title: Re: leaky exhaust in SR head
Post by: RichardL on 09.09. 2017 21:53
Do you have a finned exhaust clip? For a while I used a little rope twisted from aluminum foil and wedged between the clip and the circumferance of the exhaust port. Not as good as Muskie's method but maybe a temporary fix.

Richard L.
Title: Re: leaky exhaust in SR head
Post by: chaterlea25 on 09.09. 2017 23:52
Hi,
Yes Muskies is the "proper " cure
BUT!
Some silicone sealer can work wonders  *eek*
High temp "Dirko" is the best I have used
My old ally head Ariel defied all the other treatments until I tried the Dirko  *wink2* *wink2* *wink2*

John
Title: Re: leaky exhaust in SR head
Post by: duTch on 10.09. 2017 03:57

 The Header pipes I ranted about recently elsewhere also had inward tapers that made them loose and flappy, so I made a 'tool' that enabled me to stretch them out- much the same as Muskies suggestion, but then I had to chop them short anyway *conf*
Title: Re: leaky exhaust in SR head
Post by: Tomcat on 10.09. 2017 08:11
Expanding the pipe as Muskrat says, is the way to go. The tools aren't that expensive if you prefer to DIY. http://www.radum.com.au/product/7289-3pc-tail-pipe-expander  A bit of automotive silicone will seal the deal! The surfaces must be clean and the silicone needs to set overnight.
Title: Re: leaky exhaust in SR head
Post by: BSA_54A10 on 10.09. 2017 09:15
Expanding the pipe as Muskrat says, is the way to go. The tools aren't that expensive if you prefer to DIY. http://www.radum.com.au/product/7289-3pc-tail-pipe-expander  A bit of automotive silicone will seal the deal! The surfaces must be clean and the silicone needs to set overnight.

AT that price the tool will be trash.
I have seen a lot hat are soft cast and break the first time they get used.
A proper tool will have a steel retainer spring, not an O ring and cost near $ 200 for a single size.
The tool they show is only fit for alloy or copper tube.
It takes a large amount of force to expand a steel tube and a hydraulic expander is the only way to go
Title: Re: leaky exhaust in SR head
Post by: JulianS on 10.09. 2017 09:56
I use PTFE tape with exhaust paste. Works for me. Cheap also.

Tried to expand my pipe with a tool I got from ebay. Pipe stayed the same and the tool broke.
Title: Re: leaky exhaust in SR head
Post by: cyclobutch on 11.09. 2017 15:49
Hmmmm. The Armours pipes I bought were too fat to fit in my head. They told me my head was wrong and I should grind it out. Nice.

But maybe my pipes would be better for your bike (I never used them of course)? I could have a measure. Not sure about costs of posting to Denmark, nor on how they might not have the right bends (see other ongoing post on this).   
Title: Re: leaky exhaust in SR head
Post by: bikerboy on 25.09. 2017 01:25
Being a total bodge artist at times I tapered a bit of steel bar on a lathe and hammered it into the end of the pipe when mine was like that.

It only expanded it marginally right at the end of the pipe but with the help of some silicone it sealed in the head.
Title: Re: leaky exhaust in SR head
Post by: Viking on 16.05. 2018 11:26
Qvick up date.

The leaky exhaust pipes has been a pest for long time. ( tuf tuf, sound like a steam train ).
Tried asbestos string, exhaust sealant, aluminum foil, etc.
The small bracket on the exhaust pipe, next to the Lucas horn, snapped off last weekend, and the exhaust pipe would not keep in place. Happened at 80 mph. on the motorway !!!!

Brazed the bracket back on the header pipe with SIF Bronze Brazing rods + flux. Nice fit, but the chrome was “evaporated”

Purchased fresh new British header pipes to the bike.  Same problem.
Tried the old & new pipes in the two cast iron head I have on stock: Same problem
The old and new pipe “ Made in England “ are not correct diameter to fit the heads. !
But it is typical with UK parts: Cheep, but you need to finish them off yourself !

Heated the end of the pipes to cherry red and expanded the pipes with a Rothenberger expander tool. Filed and trimmed the pipes correct round to a correct fit.
No exhaust leak, but the chrome plating was damage. The damages areal is concealed by the cylinder head and the finned exhaust clip, and will do for now.

Wish I could get stainless steel header pipes. They can be “finished” without losing the chrome protection and appearance.   
Title: Re: leaky exhaust in SR head
Post by: duTch on 16.05. 2018 13:06
 In theory (and practice) 1,3/8" tube or bar should fit snug inside the 1,1/2" headers, which is the basis of the 'tool' I made...pein a taper to the end of a bit of pipe or cut short slots in so it fits inside and use imagination (I made a tapered washer arrangement that slid inside the aforementioned tube, then wound it out with threaded bar and various nuts and washers)       *work*.... and I could control the effect
Title: Re: leaky exhaust in SR head
Post by: Billybream on 16.05. 2018 19:47
Armours in the UK provide stainless steel exhaust pipes.
Good form and fit on my Super Rocket but others have found fit challenging
Title: Re: leaky exhaust in SR head
Post by: a101960 on 16.05. 2018 20:52
Quote
Good form and fit on my Super Rocket
You must have been very lucky. Mine were absolutely dreadful. The short pipe radius where it exited the the exhaust port was way out. The finned exhaust clip would not align flush to the cylinder head because the radius was so far out, and there was a dreadful kink on the inside of the radius too. When I complained the response was:  well file a taper on the back of the finned ring!!! Oh and regarding the kink I was told that he (the then owner) had been making motorcycle exhausts for so many years that he was not going to take any criticism from the likes of me. I did have some pictures of the faults on my old PC but when the hard drive failed I lost them. Anyhow I bought a set of pipes from Cake Street Classics not stainless steel unfortunately  but they were a perfect fit in every way, and they came fitted with the correct welded on frame attachment bracket.(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2F&hash=d56b4b7995135993e6b438e299f2e6c5)
Title: Re: leaky exhaust in SR head
Post by: Sav on 16.05. 2018 21:42
Armours in the UK provide stainless steel exhaust pipes.
Good form and fit on my Super Rocket but others have found fit challenging

My Armours pipes were like a sausage up an alley, HT silicon has arrived!
Title: Re: leaky exhaust in SR head
Post by: kiwipom on 16.05. 2018 22:39
hi guys, yeah like most things today you need to modify to suit the requirements. I am going to make some stainless Siamese pipes at some time, with SS pipes and fittings available to day it shouldn't be that difficult, cut and tack all the bits then get a welder to tig it all up/file and polish. i know it sounds easy but can be done. Many years ago i did the same with mild steel fittings to make headers for the 57 ford V.8 customline that i had, of course mild steel was easier to weld up so could do it myself using oxy/acet a good wee project, cheers
Title: Re: leaky exhaust in SR head
Post by: metalflake11 on 16.05. 2018 22:45
Bathroom and kitchen sealer for me, start the bike soon after and it burns it and grips like a good 'un.

I was told to do this by a very well reputed British bike specialist firm and it works a treat for my loose pipes.
Title: Re: leaky exhaust in SR head
Post by: BSA_54A10 on 17.05. 2018 10:17
hi guys, yeah like most things today you need to modify to suit the requirements. I am going to make some stainless Siamese pipes at some time, with SS pipes and fittings available to day it shouldn't be that difficult, cut and tack all the bits then get a welder to tig it all up/file and polish. i know it sounds easy but can be done. Many years ago i did the same with mild steel fittings to make headers for the 57 ford V.8 customline that i had, of course mild steel was easier to weld up so could do it myself using oxy/acet a good wee project, cheers
That is in fact the way the bulk of motorcycle pipes are made.
The pipe makers buy box loads of standard bends then weld them together and why most aftermarket BSA piped look ( and are ) wrong because they are not triaxial sweeping bend by a pile of biaxial bends welded together.

While Bob is a PIA to deal with, he is the only person I ever get pipes made by as he has the only 3 dimensional mandrel bender I know of.
When the price come down for the 3 axis computer benders then perhaps we will get a lot better pipes but at 1/2 million a tad too expensive piece of kit for making Pommie bike pipes.