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Author Topic: Loose head pipe joint  (Read 640 times)

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Stanley

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on: August 27, 2018, 12:36:05 pm
I'm considering three methods of improving the head pipe seal on my bike. Bedding the joint with copper silicone seal, an adjustable front bracket that adds pressure to the joint, or the time-honored spring method. Of course I lean toward silicone but wonder about future removal issues.

Has anyone regretted using silicone sealant?

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Arizoni

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Reply #1 on: August 27, 2018, 12:52:29 pm
All of the silicone RTV's have a very low sheer strength so they are very poor at bonding things together.

Just a little twisting on the pipe should break it loose from the exhaust outlet.
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Stanley

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Reply #2 on: August 27, 2018, 01:01:51 pm
Thanks, Arizoni. I've always been a little shy of using goo to solve issues but I trust your judgement.
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mrunderhill1975a

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Reply #3 on: August 27, 2018, 03:18:12 pm
I have not had good results with silicon sealers, even the copper sealer blew out relatively quickly.  I believe Ace suggested using thin aluminum can to take up the space.


AgentX

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Reply #4 on: August 27, 2018, 03:55:49 pm
I would take up empty space with a shim...copper sheeting or beer can.  A little rtv can help hold that in place but I wouldn't count on it for major sealing or support.

Me, I drilled wire gauge holes in the fins (head still on the bike) and had spring tabs put on when I made my header.  Dunno a good way to do that with an existing chromed pipe though.  The factory stuff just dabs silver paint over welds tho...


pushrod

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Reply #5 on: September 05, 2018, 11:17:50 am
You might try expanding the the pipe just a hair with a pipe expander.
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tooseevee

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Reply #6 on: September 05, 2018, 01:37:04 pm
You might try expanding the the pipe just a hair with a pipe expander.

       Pushrod's right. Any muffler shop can do this and if one of the guys does bikes, they'll get interested.

        The problem is you should have the bike with you.

         I've had a lot of crazy little jobs done by exhaust system shops since the '60s (Midas and also private little shops next to the owner's house by getting to know the guys who work there. 
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cyrusb

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Reply #7 on: September 05, 2018, 02:21:50 pm
My bullet has a tapered exhaust port. The exhaust tube will at some point have an interference fit if you adjust (bend) the mounting brackets to suit this. I have had my pipe off a few times and have never had a leak . The key is to mod the hell out of the mounting tabs, yes the chrome will peel off but thats what silver paint is for.


AgentX

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Reply #8 on: September 05, 2018, 07:24:09 pm
Mine's not like that at all.

There's no telling what you'll get and every machine's particular fit is a unique meeting of irregularities between the head and the pipe.


Honestly, I've considered doing what some Triumph owners did with their later-model heads that used an interference fit--add stubs to the exhaust port to fit earlier-model Triumph clamp-on pipes.  There are a lot of kits available to do this to the triumph heads, and those could be a basis, or I could find someone to do the AL welding straight to the head.  Think I know a guy...

Could have my current header modded to fit pretty easily on that arrangement, too.  I really detest the process of mounting and unmounting the stock header.  Always have, always will.  My exhaust springs were a pretty good middle ground, though.  They're what's kept me from doing anything more drastic.

Using something that's easy and repeatable is much nicer than a magic combination of shims and goo.  My Matchless has thread-on collars, and I almost giggle when I take the pipes off.  It's just too easy.  It should not be something you have to wonder about.

I know some headers and heads don't have that issue.  But some do.
« Last Edit: September 05, 2018, 07:26:52 pm by AgentX »


Tarnand

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Reply #9 on: September 07, 2018, 11:32:23 pm
It is certainly not an ingenious solution but I thought it might be helpful.
This is what I have done and so far it works fine for me.  The attached sketch should be quite self explanatory.  The exhaust port needs to be thoroughly cleaned with steel wool and degreased with some solvent.  Next I use a hi temp silicon to form a "oring" seal.  For that I just use just a finger.  Then I wait for the silicon to SET; this is critical.  Then I carefully insert, avoiding twisting etc. not to damage the seal, the exhaust pipe into the cylinder head so the pipe edge presses firmly against the described seal.  Even though in the end the exhaust pipe is not perfectly centered in the exhaust port the seal does seem do its job quite well.  Of course there is no guarantee that it will work for everyone but in my case it DID successfully eliminate the annoying exhaust leak.  It is required to repeat the whole procedure every time the exhaust pipe is fitted.
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solg

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Bilgemaster

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Reply #11 on: September 09, 2018, 09:10:31 am
This stuff just might work

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Fire-Barrier-Water-Tight-Sealant-3000-WT/?N=5002385+3293123929+4294921279&rt=rud

I just want to quickly concur with solg's recommendation. 3M makes unimpeachably great quality stuff with "grown up" descriptions of their products' precise properties and applications--none of that "wonder potion" vague feel-good marketing crap shoveled at you in superlative heaps by other manufacturers. That's why 3M's wares are so often the go-to accept-no-substitutes gear for sailors, where knowing exactly what to expect is a life or death matter. If you've got some below-the-waterline sealant, you just want the correct 3M goo for the materials and the job and nothing else. Their various waxes, polishes and other cleaners are also second to none. They may come in bottles that have all the eye-catching sexy shelf appeal of medical supplies--no gleaming Lamborghinis or glistening leggy vixens on those labels--but they get the job done well every time.

Something like Gun Gum Paste might also do the job you describe. I used it long ago to very good effect in a Norton Commando whose rattly threaded exhaust port had been partially stripped, but if I had a choice between a suitable 3M product and ANY other, I'd pony up the extra couple of bucks for the 3M every time.
« Last Edit: September 09, 2018, 10:31:34 am by Bilgemaster »
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finbullet

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Reply #12 on: September 09, 2018, 11:19:22 am
You could use an exhaust port seal ring from an suzuki gsxr 750 (early 90ties) it is a perfect fit between the head and the exhaust pipe. It will be located to the same place as the "goo" on tarnand's pictures. Then you should fabricate some kind of spring system which pulls the pipe against the seal ring. Maybe drill holes to the head finns and get that cooler ring and make some brackets to it for those springs to attach.
« Last Edit: September 09, 2018, 11:24:35 am by finbullet »


banjelele

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Reply #13 on: September 18, 2018, 09:25:56 pm
I've decoked my 350 Bullet 3 times and finally replaced  the head. I've been able to seal it with ultra copper hi temp silicone. I had concerns that it wouldn't seal but it has worked every time. I must have been lucky and had a pretty good fit from factory.


Tarnand

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Reply #14 on: September 19, 2018, 10:44:19 am
I've decoked my 350 Bullet 3 times and finally replaced  the head. I've been able to seal it with ultra copper hi temp silicone. I had concerns that it wouldn't seal but it has worked every time. I must have been lucky and had a pretty good fit from factory.
I must be very lucky too because silicon for me also works every time ever since I am letting it harden before fitting the pipe into the head.
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