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Motorcycle Discussions => British Bikes => Topic started by: rannsachair on January 26, 2009, 09:14:48 PM

Title: T120 Tacho drive in crankcase thread problem
Post by: rannsachair on January 26, 2009, 09:14:48 PM

I have a 1969 T120, there was a slight oil leak from the tacho drive, so decided to investigate.

The left hand thread in the crankcase has been partially stripped (I suspect a previous owner has tried to remove it as a right hand thread). :'(

I believe it was a right hand thread up to 1969.

Any repair suggestions, I wondered if I strip it all down if I could get a helicoil for the crankcase and rethread it for a right hand thread and fit an earlier tacho drive?

Anyone else had the same problem or suggestions on how best to fix?

Thanks

Title: Re: T120 Tacho drive in crankcase thread problem
Post by: Hunter on January 26, 2009, 09:19:29 PM

Could you get away with ptfe tape around the thread, should work.

Title: Re: T120 Tacho drive in crankcase thread problem
Post by: rannsachair on January 26, 2009, 09:42:43 PM

Might work, but I decided to to partially strip anyway to fit new rings, valves etc. Found a tappet fitted the wrong way round that was starting to pick-up!

Engine currently has all clutch removed, barrel etc. so not too much work to split the rest for piece of mind.

So I would prefer to make a permament repair.

Thanks

Title: Re: T120 Tacho drive in crankcase thread problem
Post by: L.A.B. on January 26, 2009, 10:37:30 PM

As you are in Scotland you could try Grintriumph? They may be able to repair it, or at least suggest how it could be done?: http://www.grintriumph.com/

Otherwise try SRM Engineering:  http://www.srm-engineering.com/

Title: Re: T120 Tacho drive in crankcase thread problem
Post by: Rex on January 27, 2009, 03:37:20 PM

Don't bodge it having got that far in.
IIRC it's a UNC thread so use a helicoil insert. The one-time use kits aren't so dear anymore, but SRM (among others) do one-off repairs too.

Title: Re: T120 Tacho drive in crankcase thread problem
Post by: Hunter on January 27, 2009, 07:11:00 PM

Quote

Don't bodge it having got that far in.
IIRC it's a UNC thread so use a helicoil insert. The one-time use kits aren't so dear anymore, but SRM (among others) do one-off repairs too.

Not necessarily a bodge, but I agree an expensive repair would be a more reliable solution as you have the engine in bits.

Title: Re: T120 Tacho drive in crankcase thread problem
Post by: rannsachair on February 12, 2009, 07:59:20 PM

Just visited GrinTriumph and advised to weld up and re-tap for RH thead.  Were very helpful.

Thanks :)