'48 G80 oil pipes

bushman175 · Post by **bushman175** » Sun Aug 07, 2011 7:46 pm

hello,
Help. I have a damaged crankcase where the return oil pipe attaches. I think I have a way of fixing it, but if anyone has had this situation occur, I would be pleased to hear your advice. Apparently this wasn't unusual in the '50s as Bernal Osborne comments about this problem in one of his service articles. The problem occurs whilst tightening or loosening the return pipe at the crankcase. The spanner acts as a lever against the oil feed line and breaks the crankcase. In my case, a previous owner had "repaired" with filler, and as soon as the pipe needed to be moved (to remove the gearbox)the filler broke out as might be expected.
My first question is: what thread is the oil pipe union (return). It measures 1/2" but the thread appears to be 18tpi which doesn't appear to tie in with any threads. Anyone know? Where can I buy a set of taps, and a die? And finally, if I use a length of flexible oil/petrol hose would there be any adverse effects?
I tend to ride rather than polish my bikes, so a slightly non-standard set up is fine as long as it works.
Thanks,
Rick

itma · Post by **itma** » Sun Aug 07, 2011 8:09 pm

quote: The problem occurs whilst tightening or loosening the return pipe at the crankcase.

actually its caused by tossers who can't work a spanner; get hold of a 5/16 whit ring spanner of a decent make, cut a slot in it to go over the oil pipe and you'll have no grief.

I think its 1/4 BSP thread but I will double
check.
yes you can use a flexible pipe.

wilko · Post by **wilko** » Mon Aug 08, 2011 2:09 am

One must be careful buying crankcases on ebay for this reason!The bottom fitting has an extension on it for a bit more clearance.[IMG]http://i244.photobucket.com/albums/gg3/ ... 0_0713.jpg[/IMG]

Don Madden · Post by **Don Madden** » Mon Aug 08, 2011 5:21 pm

The pipe is not intended to seal at the threads. They are a type of reverse flare, I have heard referred to as an "olive" fitting by Brits. It is similar to the AN compression fitting used later which had a sleeve slid onto the pipe that is sealed by compression when tightened. Both need to be tight to seal so not helpful in your situation. You need to seal the pipe end to the crankcase so will have to experament with plastic type sealers such as Three Bond, which is resistant to hot oil. The good news is that the return is a low pressure system so be sure there is no restriction at filter or otherwise. Cheers, Don.

clive · Post by **clive** » Thu Aug 11, 2011 10:51 pm

someone did a repair on a crankcase on a bike I bought many years ago, ran it for a while before replacing the cases and of course the damaged one has been on the shelf since. Looking at it I see the fix was done by using a short pipe with a thread on the outside of it. Presumably a similar thread was cut into the case and the whole lot has then been glued into place. If I remember correctly the pipe was then connected by a rubber one run to the tank. Its a bit ugly but well hidden when on the bike.