Forum

[Rattlebattle]

Yes, that is a known issue. The groove machined into the plate is wider than the o ring usually supplied. This results in a small leak which some owners, and possibly dealer “mechanics”, then try to stop by tightening the two bolts a little more. You can guess the result. The oil filter plate o ring sometimes leaks for the same reason. On the main drain plug the problem is not helped by the RE manual advising the use of thread sealant. I’d rather put up with what isn’t usually much of a leak than stripped threads. In my experience they usually seal themselves anyway.
As has been said, there are many happy owners who have had no issues with their UCE singles, but there are a lot of low mileage ones for sale out there too. As most will know, they are not making any more 500cc bikes, probably because they wouldn’t pass Euro V and, more importantly, the Indian equivalent. These bikes are likely to become similar to the iron barrel models, eventually reaching classic status in their own right. I’m keeping mine because I now know its internal condition, it’s been upgraded bearing and exhaust valve-wise and it’s really handy for local and winter use and is just so easy and convenient to ride on my own ( ie not with other riders). For me it really isn’t a suitable candidate to be my only bike or to do serious mileage on, solo let alone with a pillion, but for light local use it’s fine.
BTW I wouldn’t take pleasure in someone’s misfortune with their bike, whatever it is. I know just how depressing it can be, forewarned or not.

[windmill john]

Thanks RB, I do get pretty down when things go wrong.
I wasn’t aware of the strainer issue being new to these bikes. Wished I’d known before changing oil, would have used a bigger O ring.


John

[Wheaters]

There’s no reason why you couldn’t drain the oil into a clean container, do the repair and re-use it.

[windmill john]

Yes I thought that after posting.

On the off chance, does anyone have the o ring and can measure the diameter, so I can see if I have a fatter one or order one.

Thanks

John

[windmill john]

Actually ignore that. I didn’t realise the parts book online on our host’s site shows the actual O ring size!

[Harald]

@RB : The groove is not machined in the plate. The oil pump housing is made in a sand cast process leaving a rough surface. The O-ring has to seal against this rough surface on the pump side and a machined surface on the engine cover side. That is an impossible situation and a misconstruction. O-rings are intended to seal between flat surfaces. No matter what diameter the O-ring is this place is prone to leakage.
There is no easy answer what diameter exactly is needed as it depends on different facts. We have to take into account that the distance between the backside of the oil filter compartment has to be filled by the O-ring to give a reliable seal. This distance depends on fabrication tolerances, the thickness of the engine cover sealing and the thickness of the oil pump sealing between the oil pump and the crank case. A thicker sealing between the crank case and the engine cover will make things worse when using an O-ring with the factory dimensions, a thicker sealing between the oil pump and the crank case will have the opposite effect.
The factory sealing for the engine cover has a thickness of 0.4mm, while the replacement sold by Mr. H. is 0.7mm thick. Normally a good idea, but potential lethal for the engine in this special case. You may decide yourself if it would be a good idea to install this thicker sealing or not. If so, it is mandatory to have a thicker O-ring installed, too. But even with a thicker O-ring the whole system is prone to leakage as the O-ring cannot seal correctly at the oil pump side as explained above.
There are different ways to modify the system in a way that it will become leak-proof. I am just testing different solutions and will open a new topic soon discussing this issue in depth.

[PeteF]

I think Windmill was talking about the o ring on the oil strainer Harald.

[windmill john]

I was, but interesting as I’m new to these, that a thicker gasket on the rhs case will remove pressure on the oil pump O ring; well, interesting is not really the right word....

[PeteF]

I was, but interesting as I’m new to these, that a thicker gasket on the rhs case will remove pressure on the oil pump O ring; well, interesting is not really the right word....

Yes John, I'm seriously thinking of fitting an oil pressure guage

[Rattlebattle]

Yes, I wasn’t talking about the oil pump joint either, though it appears that may also be suspect. Not sure how you could plumb in an oil pressure gauge. I would have thought it would be low pressure anyway because there are no plain bearings in the engine other than the rocker shafts. It’s more about flow than pressure, though I stand to be corrected. This engine really is a weird design that nobody has rushed to copy....Presumably if the oil delivery is leaking at the pump seal the oil would leak into the outer t/s cover. Could this explain rising oil levels?
On a cheery note I’ve just read last week’s MCN in which someone has ridden a 2017 C5 a long way (10,000+) without undue problems. He only passed his test shortly before he went and learned how to change the oil en route. I notice his bike has the original silencer and is probably unmolested. I can’t help thinking that tinkering with these bikes causes more problems than it solves. Maybe just accept it for what it is, don’t take off the outer covers, change oil more often than specified or touch the EFI and just ride it??? Just a thought.