Hitchcocks Forum

Hi again. Got a severe oil leak from behind clutch area of primary. Have renewed the oil seal in the inner case, together with the crankshaft seal.and drive sprocket nut as the shoulder protrudes through the oil seal. Took it for a spin today and again lost most of the oil over the centre stand and rear tire. Any ideas to point me in the right direction please. I did notice that the sprocket nut supplied by our hosts had a longer collar than the one removed,and the felt washer inside the recess had disintegrated so I fashioned one from a thick piece of felt. (Poundstretchers floor protection pads.) Engine running really well actually but cannot use it again till I resolve this issue. All comments gratefully welcomed. REgards. Dez

These cases are a bu**er to seal. The problem is more likely to be the crankshaft seal in my experience, the clutch/mainshaft seal being higher up. I know it's a pain but I'd clean it all up as best you can and do a short roadtest with a small amount of oil and try and see where it is comimg from. Use ATF type F if you aren't already, it's red so makes the leak site clearer. And don't forget to check the main case bead seal, these can leak in the oddest places!

REgards, Mark

Thanks for that Mark, but I should have also said that a new gasket band was fitted and I used engineers marking blue on the cases to check for high spots whilst I had them on the bench.The gasket groove is good. In fact The primary
seems to contain it's oil pretty well, but my main oil level is dropping from mid way between the marks to off the stick after a short run!!

Confused. What oil is leaking? Gearbox or engine?

REgards, Mark

Hi. To clarify.seems reasonably oil tight when idling, but leaking under load appears to be ****Ing oil from engine sprocket area. I now suspect the oil level in the primary is rising. Gearbox is oil tight, but engine oil level dropping dramatically on distick.also leaks from outer case securing nut. Cheers.

Ok, I wish you'd explained that in the first place! What you have is a breather problem not an oil leak problem. Any seal will fail if subject to pressure beyond it's design and this seems to be what's happening. Sadly it's quite common on Enfield Twins and causes and cures are many so, full disclosure, what's the history of the bike, has this problem recently started and what have you done recently or had done?

REgards, Mark

Hello again.The problem occurred following an overheating event whilst on a ride in june. Bikes performance rapidly reduced,so I stopped and allowed it to cool,then carefully rode home which was only a short distance. Oil tank nearly empty.Got the bike on hydraulic table,refilled oil and started it up and oil was flung from the drive sprocket area leaving a sprayed trail on the floor below. and dripping from frame and centre stand. I stripped primary. Replaced crankshaft oil seal,clutch oil seal,fitted new sprocket nut and felt (interceptor mk1 type as Bullet clutch fitted at some time in it's life.) Stripped and cleaned crankshaft breather bolt and disc then refitted it. Engineer blued the cases for high spots and fitted a new rubber seal. I previously asked the forum about the crankshaft breather,and the general opinion was this item was superfluous and could either be refitted or blanked off. I refitted it. Just about all I can tell you,sorry. Only other mod which has been done is a carb re_sleeve, otherwise all is standard. Cheers and thanks. Dez

Hello again.The problem occurred following an overheating event whilst on a ride in june. Bikes performance rapidly reduced,so I stopped and allowed it to cool,then carefully rode home which was only a short distance. Oil tank nearly empty.Got the bike on hydraulic table,refilled oil and started it up and oil was flung from the drive sprocket area leaving a sprayed trail on the floor below. and dripping from frame and centre stand. I stripped primary. Replaced crankshaft oil seal,clutch oil seal,fitted new sprocket nut and felt (interceptor mk1 type as Bullet clutch fitted at some time in it's life.) Stripped and cleaned crankshaft breather bolt and disc then refitted it. Engineer blued the cases for high spots and fitted a new rubber seal. I previously asked the forum about the crankshaft breather,and the general opinion was this item was superfluous and could either be refitted or blanked off. I refitted it. Just about all I can tell you,sorry. Only other mod which has been done is a carb re_sleeve, otherwise all is standard. Cheers and thanks. Dez

I fear you have been barking up the wrong tree. What you described sounds like a partial seizure, this means the pistons and rings are no longer sealing properly and are allowing combustion gases to pressurise the crankcase leading to leaks in unexpected places. Given your symptoms a top end strip would be the next step in any case so I suggest that should be your next action.

REgards, Mark

Many thanks Mark. I did not think of that. While I have the top end off,can you suggest any useful lube or breathing mods to undertaken at this stage. Will do rebuild over winter and if I need any more advice I know where you are!!!🤗🤗

Thanks again. Putting you on my christmas list right now.