Hi, I would be grateful for any advice on my newly rebuilt A65 engine (by SRM)
Engine starts and runs smoothly with exception of an annoying leak which looks to be coming from the timed breather up under the engine sprocket. (very difficult to see up.
This only happens when the engine is running and is not gearbox oil (no hypoid smell) or chaincase oil. (no level drop in chaincase SAE 20 after 150 miles) Over a period of 150 or so miles running on the engine oil level in the tank has dropped by circa 5/6mm.
I dont think wet sumping as oil level does not drop over a stored period of 2 weeks and it does not smoke on start up.
Any insights as to possible causes would be welcome however I suspect it is an engine out and strip job to fix if breather parts incorrectly fitted or damaged.
Thanks,
Peter C.
I had to scratch my head to try to remember how the engine breathing is done on an A65 but assume it's through the small hole just under where the LH end of the camshaft and timed breather is. It therefore vents in front and almost just above where the engine sprocket is.
I would have thought it would be very difficult to establish if it was the breather leaking oil rather than the clutch cover or seal by just looking under the engine - both will leak down the crankcase before dripping on to the floor. In practice some oil will inevitably come out of the breather since the LH camshaft bush gets oil which will then be blown out of the breather. In contrast, on BSA unit singles, the timed camshaft breather vents into the inner timing case before exiting high up at the back which tends to catch the oil.
If it was me, I would try to eliminate a chaincase leak first either by running the engine with the chaincase oil drained out or using oil with dye in. You say that you don't think it is gearbox oil but, again, using dyed gearbox oil would be a way to be sure of this.
However, if the engine was rebuilt by SRM, is it not under some form of warranty and, if so, shouldn't they be the ones to sort out the problem?
:) :) :) :)
It sounds very much like you are correct.
To check it, I would suggest. Get a large sheet of cardboard, or similar, Put it flat on the ground then put the bike on it on the centre stand and start it. Let it run for a fair period. If its the breather you will see oil on the cardboard very soon after start up. I'm about to do the same to my A50.
A point to look for: - are there any oil "spots" on the bike after a run as if its spitting somewhere?
Mike 8) 8) 8) 8)
Good morning,
It is possible that if the engine has done very little mileage than the rings are not yet bedded in. If so, then there could be a bit of pressure building up in the crank case. This could also contribute to a bit of extra oil consumption.
As suggested by Spaceman, contact SRM to see what they say.
Dave.
Gents,
thanks very much for the expert feedback. I will carry out the checks suggested before getting back to SRM with the full picture.
Thanks again
Peter C :)
:) :) :) :)
Hi Dave.
I'm hoping that my problem is simply un bedded pistons. My motor has done next to no mileage since rebuild. I certainly don't want to drag it to bits again at this stage.
I would certainly tell SRM of the problem and ask their advice. by email you then have proof of conversation. Etc. Tho with them I doubt you need it. Its insurance. If it aint in black and white, it aint been said.
Mike 8) 8) 8) 8)
If it does turn out to be excess oil being forced out of the engine breather then, assuming the LH camshaft bush isn't badly worn, I would have thought it must be due to excess oil getting on to this bush. Normally, the oil gets on to this bush mainly from being thrown off the LH big-end due to the oil pressure. If the big-end bearing was very badly worn or the oil pressure was excessively high then this could cause problems but that should not be the case here because the engine has just been rebuilt?
However, another reason for excess oil being thrown around the inside of the engine is if the oil in the bottom of the sump is not being scavenged properly and is being thrown around by the crankshaft fly weights finding themselves rotating in a pool of oil. I would therefore definitely check the scavenge side of the lubrication system and make sure the return to the oil tank is behaving normally - that is, after running the engine for a few minutes, it settles down from a continuous flow to spurting regularly.
Ideally, it would be worth checking that, after warming up the engine, there is no significant amount of oil in the sump when you stop the engine to show there is a scavenge problem. Unfortunately, on a BSA that is not so easily done, because they aren't fitted with a drain plug!
Hi,
As the engine was built by SRM they may have fitted one of their after market sump plates. Personally, I would contact SRM before taking a spanner to it. Any DIY may nullify any warrantee on the engine.
Dave.
I would have thought it highly unlikely that there is an engine problem because SRM have an excellent reputation. However, it might be possible to get this issue if the engine is not able to properly scavenge the oil in the sump because, for example, of a problem with the oil pipe back to the oil tank being partially blocked. That's why it might be worth doing the scavenge checks just to rule out this possibility. Apart from removing an oil drain bolt, if it has one fitted, it doesn't really need the engine to be touched in any other way!
Thanks again guys. Much appreciated.
I fitted an in line car type oil filter in the return. Maybe this is impacting oil return. It also has an SRM sunp plate and with drain plug fitted. I will drain and check qty of oil in sump tomorrow and also the return flow checks suggested.
Otherwise it is totally oil tight.
Thanks
Peter
:) :) :) :)
I'm interested in this as I also have an in line oil filter fitted. SRM bumf advised not to fit one so if you are thinking of removal please keep us informed. Tho I must say my return flow is satisfactory in all ways.
Mike 8) 8) 8) 8)
PS did you check against oil on the ground from breather outlet.
The breather hole at the end of the camshaft is the method used for crankcase breathing. The problem is lots of factors can make the pressure greater or smaller, such as blow by due to worn bores etc.
The A10 and Triumphs all have a similar set up. Oil will be evacuated via this and depending on the above, it may be a slight mist or alot greater. Either way, oil will end up on the floor to some extent.
My solution was described by Cliff Page in the March 2022 Star titled 'Unit Twin Crankcase Breather evacuation'. This works in that any quantity is prevented from being plastered all over the front of the gearbox part of the engine casing and then dripping off.
By fitting such an arrangement, you will be able to monitor how much is being chucked out and if excessive, at least you will know there is an issue.
The other possibility is if the SRM or other sump plate with a magnet in the plug is fitted. If such an item is fitted with the drain hole close to the suction pipe (with the non return ball in the end) then the magnetic field from the plug may be strong enough to hold the ball down and prevent it from lifting, restricting the suction flow, causing the crankcase to have more oil than desirable or intended, so worth considering.