My bike has had the gearbox drain hole rethreaded with a very fine thread which is crossed, consequently the drain plug I have does not fit flat with the casings.Can anyone advise me what size and thread the drain plug shoud be.I am hoping I can obtain a tap / helicon like to try and repair it.Thankyou Gordon
The gearbox drainplug in a plug within a plug. The larger, outer one has a standpipe for filling to correct height. Is that the one that's stripped or is it the inner drain.
If you're fixing with correct new parts, the vendor will tell you the size and thread (I believe it may be 9/16" and 16 thread/inch.)
Do yourself a favor and buy or download a parts and repair manual.
Unfortunately the previous owner has put one single bolt in,there is no drain pipe just the one nut which as I say is cross threaded.
Hi Gordon,
I think that '66/'67 saw a change in the oil level and drainage arrangements. This may have resulted in a change in thread for the drain plug hence if the wrong one is fitted then it may have been forced to fit, hence a rethread.
Is your oil filler in the inner timing cover and have a plastic cap/dipstick? This would have a plain drain plug.
If the oil filler is in the top of the gear box and is a metal cap then the plug in the bottom is a drain plug with a level tube built in. Unfortunately I do not thread specs. but they could well be different. The later ones are and would not go in without a struggle so again perhaps the wrong one forced in. My '67 parts book has both setups in.
Dave.
Thanks Dave,mine a 66 has an aluminium screw in filler plug in the top of the engine,no dip stick,and as I say a plain drain plug in the bottom,pictures I've see of drain /oil level plug are all a much coarser thread.I will have to measure the drain hole and see what size I can rethread it to,once again many thanks.Gordon
I think you may struggle re threading without pulling out the gear assembly. There is not a lot of room from the plug opening until you hit something inside!