Oil in cylinder

[bazajay]

Help! I am really starting to go a bit crazy with my bike. The problem - oil in the chamber. I have a 49 18s - total rebuild. The bottom end, cylinder, bore and valves were all done by an excellent engineer, all the bits are new from the club, and the cylinder is rebored with a new piston. New valves,guides, hairsprings everything new. It came with an alloy head (not correct for the year but thats ok for me).
All was going great I have been kicking it over quite a few times before it goes on the road proper. (Not letting it run too long, air cooled and all that)

UNTIL a few days ago I noticed a black sludge coming from the exhaust port. Okay a bit over oiling but not too bad. I first thought it was the exhaust valve over oiling but then I took the head off and the top of the piston was really dripping with oil. Okay new rebuild, all parts nicely oiled while building there is bound to be some oil around to burn off. But after looking at the top of the piston with the head off it was swimming in the stuff. And I have ran it enough times to burn all the rebuild oil off.

Okay time to restrict the oil a bit so I have;
First thing, inlet oil metering screw - turned it right in.
Little resevoir with hole for Ex valve restricted via plug with flat side.
Oil way by the cylinder base plugged (getting desperate)
Breather checked and even left the rocker inspection cap loose to relieve extra crankcase pressure.

The oil flows really freely through the two jets by the rockers (right hand one was blocked when I got the bike so I freed it and it really gushes out now)

Where is the oil coming from - I looked at the piston but couldn't tell if any rings were upside down (anyway rings wrong way round on a new piston -unlikely).

Also it not wet sumping.

Please ANY tips or tricks to help me find where the oil is coming from would really help my mental state!
After SEVEN YEARS work I was ready to go and have my beloved bike on the road but then this!!
HEEELLLPPP!

[Dixter]

Hi Barry, the first thing I'd check is too much oil in the crankcase. When there is too much oil in the crankcase, the flywheels sling massive amounts of oil up the cylinder, the oil control rings on the piston are unable to properly clean the walls, and the piston pushes the oil out the exhaust port, and oil drips from the exhaust pipe / cylinder connection.

This can happen from too much oil in the crankcase upon initial start up, from over flooding the cam case upon assembly, or over oiling the valve gear on assembly. Worse case is scavenge pump not properly clearing the crankcase.

I'd start by draining the crankcase. Starting the engine, and allowing to run at idle or slightly above, and observing the return of oil in the oil tank. Keeping a fan on the engine is recommended. If the oil filter gallery was not filled upon start up, oil return seen in the tank filler opening may take upwards of 4-5 minutes. On a new rebuild it will seem like a lifetime, but is normal. These pumps are notoriously slow.

The classic symptoms of oil flooded crankcases are, 1. Oil dripping from exhaust port. 2. Upper throat of the crankcase, like where the engine serial number are stamped, far too hot to touch after a 5-10 minute ride. 3. More than 2 or 3 fluid ounces of oil drain from the crankcase, when checked “immediately” after a 5 minute ride.

The reason the crankcase over heats is vast quantities of superheating oil from the underside of the piston over heat the crankcase.

Let's take this is steps. Make the above checks, report your findings, and we will concern ourselves with the oil pump later. It may be just too much oil on startup, and a drain will resolve the issue.

Ciao, DC

[SPRIDDLER]

In the silence, except for Dixter's thorough reply, you should be able to hear some of us scratching our head.
I can only add my ramblings of random thoughts.
Is the bike new to you? Or rather, did you have the engine running without this problem prior to the rebuild?
You mentioned that one of the jets at the rockers was blocked but now cleared and I freed it and it really gushes out now. Could the PO have blocked it to try to reduce the over-oiling?
When you loosened the rocker cover to help reduce any c/case pressure did you leave it loose for very long? I only mention it because our Worthy President had a similar problem last year. He found that when the 'O' rings at the base of the pushrod tubes were compressed they had distorted inward, partially blocking the drain holes. Oil puddled in the rocker box instead of running freely down the p/rod tubes, apparently causing severe over-oiling in the cylinder.
Of course the new piston is the correct oversize for the re-bored cylinder (silly thought ) but the rings will take a while to bed in, although there seems too much oil getting in the cylinder for that to be the cause.
Is the inlet valve metering screw correct? It should have a pointy end:

inlet valve oil dims 009 (840x630).jpg

[Mick D]

The oil flows really freely through the two jets by the rockers (right hand one was blocked when I got the bike so I freed it and it really gushes out now)

Hi

For me this is the pointer.

If oil is gushing out of the rocker feeds then too much oil is being pumped to the rocker box, my feeds just drip every few seconds.

If the flow to the rockers is too great I'd be investigating why, (as it means the flow to the bottom end is incorrect and possibly starving it).

Quick check would be to separate the rocker feed pipe at the rubber sleeve, start the engine and observe the oil flow from the pipe, it should be minimal and you should be able to stop the flow with finger pressure. If not I'd strongly suspect a blockage in the bottom end feed from the pump to the timing side bush or onwards in the galleries inside the crank shaft, if there is a restriction here the pressurised oil will be forced to vent via the rocker feed.

Regards Mick

[bazajay]

Thanks so much for the replies, in response; there is not to much oil in the crankase, I have ran it then checked the level several times (also after standing overnight) the most I get out is about a third of a tea cup which I think is okay. Yes Spriddler I have ran it for quite a while with the top of the inspection cap ajar, letting extra pressure out and the metering plug is new and pointy.
Mick D I think you may have a point because there is so much oil dropping on to the rockers, especially the Ex rocker. I am going to test this later by doing what you said with the rocker box oil pipe. I am really scared about this because wouldn‘t that mean a complete strip down. Aw my god the thought of it makes me ill!!! Or are there any tips for such a problem?
I shall report back later on the oil test, one tiny hope is that if I block the rocker oil pipe for a bit (there's plenty of oil in the top end to let it run ok) it may dislodge the blockage or is this only an (oil) pipe dream, you have to laugh or else you cry - which will be me if the bottom end is blocked!
Thanks again and it is wonderful to think at least I am not alone!
Cheers - Barry

[Mick D]

Hi Barry

Look at it this way, if you strip it down to discover the cause it will be a lot less heart breaking than if you strip it down to remedy the result of a blockage.

My diagnosis could be incorrect but you certainly seem to have an excess of flow to the rockers and if this is the case the only place it can be depriving oil of is the bottom end.

Regards Mick

[SPRIDDLER]

Indeed, oil 'gushing' from the rocker after you cleared the 'blockage' isn't right.
Don't like to be negative but if the timing side bush has rotated (it should be pegged in place) then its cutaway would become out of register, inhibiting bottom end oiling and over-oiling the top.

[bazajay]

20200308_112702.jpg

Just tested the oil flow to the head, disconnected it and looked at the flow I have attached a pic - is this normal? I could put my finger over it and I could stop it ok and it didn't squirt past my finger. this is the flow with a pretty fast tickover. What do you think. Hi Spriddler I was with with the mech when he pegged the timing bush so I don't think it is that.
Anyway what do you think about the flow, I think it is not excessive - but then again I have no experience to say what is normal!
Cheers again - Barry

[bazajay]

Just thinking about testing the bottom end oil flow, if I stopped the oil flow to the rockers, by letting it flow into a jar (bearing in mind I have blocked the flow at the cylinder base - the one that used have the ball in) is then the only oil path working the one to the big end? If I drained the crankase before starting (just to make sure)and as I said stopped the rocker oil flow would I see oil returning to the oil tank if the big end isn't blocked?? Or is the flow to the big end so minimal i wouldn't see any anyway?
Your thoughts would be much appreciated!!
Regards Barry

[bazajay]

Me again.. (hope I‘m not just posting to myself!) just did the aforementioned test (rocker feed into a jar and checking oil return to tank) and there is a flow, obviously reduced but a good trickle. Emptied crankcase beforehand and let it run for 3/4 minutes and the oil kept returning. (Please oh motorcycle god in heaven let my big end oil feed be free)!
So I hope its not a blocked big end feed - thoughts?
Again thanks all!