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Motorcycle Discussions => British Bikes => Topic started by: tractorman on January 20, 2011, 06:20:48 PM

Title: Triumph crankcase damage
Post by: tractorman on January 20, 2011, 06:20:48 PM

On stripping a pre-unit Triumph engine I find damaged to the crankcases and I am trying assess how important a repair would be. On the inlet side, the internal bosses that surround the tappet block and are joined by a ¼" screw have broken off at some stage. As these don’t actually clamp or support the tappet block, I wonder if they are really important and I need not worry about scrapping the cases or getting the area built up with alloy weld and re-machining the opening and screw drilling.

Any thought please

Title: Re: Triumph crankcase damage
Post by: rogerwilko on January 20, 2011, 09:24:45 PM

Show us a picture please.

Title: Re: Triumph crankcase damage
Post by: tractorman on January 21, 2011, 10:43:21 AM

I wish I knew how. tried advanced options, isert image, broused to file. Its a 114KB .jpg file, but I get the error message "the attachment upload is not writable"

Title: Re: Triumph crankcase damage
Post by: VintageBike on January 21, 2011, 01:44:00 PM

Hi,
I'll take a look at this problem now.  We moved the website last night to improve performance.  I'll PM you when  its fixed.
Sorry for the inconvenience
Nigel

Title: Re: Triumph crankcase damage
Post by: VintageBike on January 21, 2011, 01:58:54 PM

Should be OK now, but if you have any problems, please let me know.

regards
Nigel

Title: Re: Triumph crankcase damage
Post by: esometisse on January 21, 2011, 06:56:39 PM

these bosses don't serve any purpose regarding the tappet blocks as these are held in the barrel base flange. The likely cause for their breakage is that someone has forgotten to remove the bolt prior to separating the cases.
These two small bolts are only there to strenghten the crankcases a little. If they are really doing any good in this respect is anybody's guess especially when you consider that they are not present at all in the later unit construction crankcases (1971-on I think).
If you are building a standard engine (no excessive power or torque) I wouldn't worry too much about the absence of these bolts.

Cheers

Title: Re: Triumph crankcase damage
Post by: tractorman on January 21, 2011, 07:45:09 PM

OK lets try again

pictue of damage

Title: Re: Triumph crankcase damage
Post by: Revband on January 21, 2011, 08:55:15 PM

Yes not a pretty site is it?.

I would expect that the only real problem with not repairing this area is that you will have great difficulty making it oil tight.

Title: Re: Triumph crankcase damage
Post by: Rex on January 21, 2011, 09:46:26 PM

But that's on the inside of the barrel, so oil tightness isn't an issue.

Just use it. You'd be amazed how many Saturday morning mechanics forgot that screw, inserted large screwdriver and heaved until the lug broke off.
No biggie, just looks crap while you're rebuilding it.. ;)

Title: Re: Triumph crankcase damage
Post by: rogerwilko on January 22, 2011, 12:56:12 AM

Out of sight out of mind!

Title: Re: Triumph crankcase damage
Post by: Revband on January 22, 2011, 04:27:52 PM

This post was incorrect and misleading, corrected by Rex below. So I have removed it, Sorry

Title: Re: Triumph crankcase damage
Post by: Rex on January 22, 2011, 06:06:19 PM

Nah, the tappet block is a tight press (bash) fit in the cylinder block. This hole formed in the cases just allows the tappet guide block/tappets  "access" to the cams. The tappet guide block isn't a tight fit in the c/cases.

Title: Re: Triumph crankcase damage
Post by: Revband on January 22, 2011, 08:25:58 PM

Hmm, obviously the memory is not fully up and running today.  :-[

Thanks for correcting me on that, no beer tonight then and it may work better tomorrow. :)

Title: Re: Triumph crankcase damage
Post by: tractorman on January 26, 2011, 01:46:07 PM

many thank guys.
consensus seems that Triumph wasted time and metal in creating these lugs
so I will cut off the piece left, [before it vibrates off and does more damage]
tidy us the ragged bits and put back together.