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Possible Exhaust Leak
#796360 01/23/20 3:46 am
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mrcarb Offline OP
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When the throttle is twisted on my A65 it sounds like there is an exhaust leak coming from the head area. Would someone here have ideas on how to repair this? Tighten the exhaust pipes somehow?

Thank you in advance.

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Re: Possible Exhaust Leak
mrcarb #796368 01/23/20 7:53 am
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Different methods,

Buy a pipe expander. -best way.
Or

Ptfe tape around the pipe, or rtv silicone.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Possible Exhaust Leak
mrcarb #796375 01/23/20 10:11 am
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As previously mentioned, expand the pipe till it just won't go into the port
Start the bike and warm the head turn off & fit quick then leave the whole shebang to cool down.
Most specialist muffler shops will expand the pipe for a few bucks or some cold beer.


Bike Beesa
Trevor
Re: Possible Exhaust Leak
mrcarb #796381 01/23/20 1:06 pm
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After you get the pipe fitting better, make sure all original mounting point
are used for entire exhaust.


Bill
1974 Norton Commando
1966 Lightning
1965 Lightning Rocket
1966 Norton Atlas
1967 Norton Atlas
1948 Panhead
Re: Possible Exhaust Leak
mrcarb #796430 01/23/20 10:26 pm
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ptfe tape around an header pipe? cant see how that would last more than 5 minutes .........?but then ive never tried it ............you used to be able to get this stuff in a tube called fire gum ive used that


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: Possible Exhaust Leak
mrcarb #796432 01/23/20 11:35 pm
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RTV106 is good for 500 deg. F. Loctite 596 is good to 600 deg. F. Not too much or you will need a torch to burn it out or put the head in concentrated sulphuric acid. Resistance to gasoline is poor so you might be able to loosen it by dropping the head and pipes into a bucket of that.
If you do not need to keep it original you can have spigots put in the head. Plain spigots with push-over pipes or spigots with a female threaded ring and male threaded pipe.

Re: Possible Exhaust Leak
Ignoramus #796458 01/24/20 7:35 am
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Originally Posted by Ignoramus
ptfe tape around an header pipe? cant see how that would last more than 5 minutes .........?but then ive never tried it ............you used to be able to get this stuff in a tube called fire gum ive used that


Depends how big the gap

I used it year ago on a WDB40, it was loose enough to send flames out of the silencer on over-run. It solved the problem. This was before I learned that RTV sealer would do the same job and used that since if it needed it.

Last edited by Allan Gill; 01/24/20 12:53 pm.

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Possible Exhaust Leak
mrcarb #796460 01/24/20 10:09 am
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Fire gum is a pain, it works but once it fails then getting it cleaned up is a real pain, RTV bathroom silicone works just as well and is easy to clean up.

Re: Possible Exhaust Leak
mrcarb #796478 01/24/20 4:06 pm
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Years ago I used to cut strips of aluminum from coke cans, wrap it around the exhaust and force it all into the head, seemed to work but OK but only if the exhaust port was sufficiently worn.

Subsequently I've tried fire gum but never really succeeded in getting a good seal as it sets hard and doesnt flex.

RTV works best and is simple to apply, I've never had a problem removing it, seems to scrape away quite easily with a knife. I've never tried the bathroom version of RTV and usually use Loctite 5990 Copper high temp RTV which is cheap enough.


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: Possible Exhaust Leak
mrcarb #796491 01/24/20 9:05 pm
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I'll try the pipe expander. I am thinking expand the pipe until it just fits into the head or else it will not fit. Any comments about the size to expand it to?

Re: Possible Exhaust Leak
mrcarb #796493 01/24/20 9:22 pm
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It won’t be an easy task to expand a chromed pipe with a normal pipe expander, so open it up best you can and keep trying for size, also wear in the port will make the size individual to your pipe. You will also find that the pipe will flare, if you put enough of the expander in to spread the pipe properly you will most like bust the expander (mine broke after doing a couple of sets). You’ll most likely get about half of the length of the expander in and the pipe will flare instead. But this is fine!

Also to stop the end of the pipe becoming octagonal in shape, open it up and bit, then back it off and turn the expander a bit and wind it open again, it’ll stop this.

Hth


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Possible Exhaust Leak
mrcarb #796509 01/25/20 2:09 am
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Not to take anything away from the solutions outlined above, I thought I might add a "quick and dirty" fix, perhaps a temporary fix if one is needed until a more permanent fix is employed.

It's called "fingertip caulk", a putty-like substance that's used to seal up storm window or storm door frames. It comes in a roll, and you can shape it with your fingers. The idea is to roll a bit of this stuff into a thin ribbon, wrap it around the header pipe at the head, and then shove the heat sink up against it, forcing it into the space between the header pipe and the exhaust port.

The caulk does deteriorate after a while, gets brittle and cracks. I find I have to redo mine twice a year. But it's an easy job and the fingertip caulk comes in a big roll, cheap. I've been working on the same roll for many years.

There was a product specifically designed for this purpose; I believe it was called Moto Seal, but I don't know if that or any equivalent product is available today.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: Possible Exhaust Leak
mrcarb #796530 01/25/20 8:42 am
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Do your down pipes have a balance pipe or tie bar fitted? If not it would be worth looking at doing so, the lack of support is probably why they wear so poorly in the first place.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Possible Exhaust Leak
mrcarb #797147 01/31/20 10:47 pm
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I am thinking that the pipe should be expanded so that it just fits in the hole. Also it sounds like a good tip by Allan Gill to expand the pipe a little and then back out and rotate the expander and do it again to prevent the pipe from becoming octagonal in shape. My pipes have the connector pipe between them which may make a difference.

Thanks for the replies!

Re: Possible Exhaust Leak
mrcarb #797149 01/31/20 11:01 pm
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expand the pipe , clean the port with a rotary steel brush till all is shiny bright, then wipe it clean with petrol 3 times, , let dry , wipe down with vinegar.
Apply a bead of bath sealer in your colour choice to the port and a second bead to the cleaned pipe, be generous.

Push the whole lot together and wipe up with a rag soaked in vinegar.

If its really bad , like mine , make up shims from beer cans to take up some of the space. try not to cut yourself.

On my bike , no beer can shims . lasts less than 2k, beer can shims, lasts ages longer than strip downs.

All silicone RTV sealers will take exhaust temps. hi temp stuff is snake oil.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod

Moderated by  Allan G, Jon W. Whitley 

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