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tribsa alloy 8 stud pre-unit head #714366
11/09/17 11:45 am
11/09/17 11:45 am
Joined: Nov 2011
Posts: 141
kelso scotland
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yosemite Offline OP
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yosemite  Offline OP
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Posts: 141
kelso scotland
Hi
About to start rebuilding the Tribsa engine, but the head needs sorting, usual cracks and the threads in the exhaust ports are not really useable, apart from filling the ports with weld and recutting the threads in a milling machine,apart from this, so far I have thought about about using alluminium brazing rods, and simply filling around the stub, (but not sure the repair will survie the temperature when the engine is run.) or simply boring the port and using a push in stub.
Any suggestions as this bike is a tribsa not really bothered about originality but any repair must be durable
To fix the cracks was going to ream the holes and make a couple of steel hollow dowels to press in
Yosemite

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Re: tribsa alloy 8 stud pre-unit head [Re: yosemite] #714668
11/11/17 9:32 pm
11/11/17 9:32 pm
Joined: Nov 2009
Posts: 622
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bon Offline
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If you go onto "gordy's goodworks" on youtube, you will see how he does it. If it were me i'd bore out the ports and weld in a fresh piece of aluminium and recut the threads.

Re: tribsa alloy 8 stud pre-unit head [Re: yosemite] #714848
11/13/17 1:06 am
11/13/17 1:06 am
Joined: Aug 2012
Posts: 122
AR
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bryan johnson Offline
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have you thought about just using this as an excuse to switch to a 9 stud unit construction top end?

Re: tribsa alloy 8 stud pre-unit head [Re: bryan johnson] #715005
11/14/17 10:25 am
11/14/17 10:25 am
Joined: Nov 2011
Posts: 141
kelso scotland
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yosemite Offline OP
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yosemite  Offline OP
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Joined: Nov 2011
Posts: 141
kelso scotland
Originally Posted by bryan johnson
have you thought about just using this as an excuse to switch to a 9 stud unit construction top end?

thought about it , still thinking but would need 9 stud barrels,and would probably end up putting a big bore kit on it, high comp pistons.......

Re: tribsa alloy 8 stud pre-unit head [Re: yosemite] #715210
11/15/17 2:51 pm
11/15/17 2:51 pm
Joined: Aug 2012
Posts: 122
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bryan johnson Offline
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It is a slippery slope...

Re: tribsa alloy 8 stud pre-unit head [Re: bryan johnson] #715227
11/15/17 5:21 pm
11/15/17 5:21 pm
Joined: Nov 2011
Posts: 141
kelso scotland
Y
yosemite Offline OP
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yosemite  Offline OP
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Joined: Nov 2011
Posts: 141
kelso scotland
Originally Posted by bryan johnson
It is a slippery slope...

maybe nows the time to take up a new hobby.......skiing

Last edited by yosemite; 11/15/17 6:35 pm.
Re: tribsa alloy 8 stud pre-unit head [Re: yosemite] #734588
05/09/18 7:04 am
05/09/18 7:04 am
Joined: Aug 2014
Posts: 981
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Les P Offline

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Les P  Offline

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How far gone are the threads, you might get away with an oversize spigot ?


More bikes and projects than you can shake a stick at but they should be done in two shakes of a lamb's tail.
Re: tribsa alloy 8 stud pre-unit head [Re: Les P] #735276
05/14/18 6:58 pm
05/14/18 6:58 pm
Joined: Nov 2011
Posts: 141
kelso scotland
Y
yosemite Offline OP
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yosemite  Offline OP
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Joined: Nov 2011
Posts: 141
kelso scotland
The threads in the exhaust port are too bad to use an oversize stub, the cracks are the usual ones from the valve seats to the bolt holes, but the rebuild has had to be put on hold, due to having to spend time working on the new house



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