Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 head oil leak

I have had a problem with my head gasket leaking and dripping a bit of oil on the left rear of the barrels from the time I got it about two years ago. When I pulled the head I found that it was about .004" high in the center between the two cylinders.



Sent the head to Ed V for some head work and he also surfaced it at that time. I had the barrels top surfaced here by a shop. New head bolts and studs. The cylinders were a bit glazed so had them honed at 170 and installed new Hasting rings I annealed and used my old head gasket that was in good shape. After 300 miles I have good compression, 165 on each side. Right plug is nice and clean but the left is a bit wet with oil, but getting better.

Have been doing an aggressive break-in but have held the rpm's below 4,500 till yesterday when I took it to 6,000. When I got home and looked down to shut off the gas, this is what I see.



The head gasket is nice and tight not a bit of oil to be found anywhere. I didn't install O-rings in the two small oil weep holes from the head, but then again like I say not a hint of oil from the gasket. I am at a loss as to what is going on here

That isn't unusual, it's just coming up the stud. Take the nut and washer off clean them and the stud and put some sealant under the washer and nut and on the thread and re-torque the nut.
My guess to why oil leaks there is compression gets past the gasket to the stud then comes up the stud and thread. If it comes right across the gasket it will weep oil between the head and cyl and you would need to pull the head off to fix, it's not worth doing that for this sort of leak, I always put sealer on those nuts and washers when I refit a head.

Thanks Mark...but where would that much oil be coming from?

Went for a ride this past Sunday and bike was running great for about the first 10 miles when all of a sudden ( more like instantly) it started to crap out on me. It was like it was running on one cylinder and only firing intermittently on that one cylinder. When I would pull the clutch in and feather it a bit I could keep it running. Didn't think I was going to make it the 3 miles home but playing with the throttle and clutch I could get the RPM's up. After a mile or so I got it running fairly strong but it was still missing and cutting out at times, got home, shut it down and walked away from it and went inside. The entire time while I was trying to get home I was thinking it was something electrical like one coil might be bad or an intermittent short. Next morning went out and it started on the first kick, ran fine and took it for about a half mile ride. When I got back it would start to die out at idle, could keep it running fine with some throttle.

Some background on what I have been dealing with are stated in the first part of this thread, basically high oil consumption, high carbon build up on pistons after only 1,000 miles.



The right cylinder seams to be fine, the plug is nice and dry with a light yellow tan color. The left plug is very wet with oil. This is the side where the oil was coming up through the stud. That is a lot of oil to be coming out in a short run at 6,000rpm.

Are there not only three places it could be coming from???

One... valve guides (new valves, guides, and springs by ED-V)
Two... bad rings (new Hastings) Yes the beveled side was up
Three...from the head oil weep holes to the cylinders

Is there enough pressure to push that much oil past the gasket at the weep holes? Both surfaces where skimmed. I just cant see where this much oil is coming from. Could a badly fouled plug have caused the motor to fire on one cylinder? I know it will on a two stroke. When I pulled the head today the gasket looks fine, but there was a lot of oil on the top of the pistons and down the sides of the cylinders as well. The last two times I have pulled the head all was dry in side, not this time.

I am just about at the end of my rope with this thing, any help would be greatly appreciated.

You have five head bolts inside the valve area that can leak oil down to the head gasket. Once there, combustion gas can blow it between the mating surfaces and out where ever it is not sealed. Your middle pushrod tunnel bolt hole looks wet, with oil?
It does not look as though you used Copper Coat on the head gasket. You can also use Locktite Gasket Eliminator on both sides of the gasket. Use it on both sides of the head bolt washers also. Those surfaces are often beat out from people over torquing the bolts thrying to keep it from leaking rather than fixing the problem. You should see impressions of the head and cylinder machining marks in the gasket if it was annealed properly. Annealed copper is very soft but work hardens quickly if bent.
I do not see how the right plug can be fine with that much oil coked on the piston.
Did you have the head checked for pin hole porosity leaks? One way to be sure is to paint the inside of the head with Gyptal which also helps the oil return.

Just a adition to what DMadigan says:
AFA I can see it on the photo of the carbon on the pistons,
the head gasket has not been tight around the threaded hole
in front of the pushrod tunnel and between the pushrod tunnel and the cylinders.
That's where the oil comes from.
The bolt hole corresponds with the bolt deep down in the head which is sometimes forgotten at retorque.
If that bolt is too long, it touches the bottom of the hole and does not push the head down.

Yes that will foul the plugs and cause the misfiring. Cylinder pressure will push oil up a stud even with very little oil being in the cyl. Too rich a mixture will cause plug fouling as will excess oil which can enter the cyl through guide to valve clearance, guide loose in head or lack of ring seal are the main most common reasons. If the oil drain holes in the front of the head/block leak it leaks out the gasket at the head joint at the front. If it wet sumps it will force oil up past the rings. This can be checked by checking oil level before and after riding the bike, if the level is higher when you arrive back from a run, the extra oil was in the sump. If its overly rich fuel will wash the oil off the bore. Have you opened the throttle a bit running it in? Cyl pressure gets behind the top rings and pushes them against the bore helping them bed in, if its babied too much they might not bed in very well.

Thanks for the help guys...should have been more clear on the photo of the head gasket. That was taken the last time I had the head off trying to stop the leak from the gasket at rear of the left cylinder. There was about 3,00 miles on it at that time. Was just trying to show how much carbon was building up

This picture is 300 miles after having the head and cylinders skimed,new valves and guides done along with the new head bolts, studs, and new rings. Again in the pic with the oil on the fin, the oil only started to show up after taking it to 6K for the first time at about 250 miles. Never showed oil there till then although the left plug was quite wet from the start.



I didnt take this pic. right after pulling the head so put the gasket back on for this shot. It might be upside down from the way it was on when I pulled the head. So looking at the right side here might be the left cylinder. The front bolt and stud for the left looks like there might have leakage. Would the oil be pulled into the cylinder from the bolt and then pushed out the outside stud as in the first pic?


I used a Napa product made by Permatex called Copper Spray-A-Gasket on both sides of the gasket and on the head and cylinders.
I can see some impressions in the gasket.
Will use some Gasket Eliminator under the washers and bolt heads. Will it still seal under the washers and bolts after retorqueing the head at 100 miles?


Like I posted earlier....I have new guides, valves and springs by Ed-V
I might be running a bit rich...this is a Thunderbolt and should have a AMAL 928, I got it with a new 930 on it and has been running fine but on the slightly rich side. Again the right side plug has good color to it. I have been thinking of getting a new 928.


It wet sumps a bit not much over a week to ten days.
If it wet sumps will it not smoke a lot at start up? This one doesn't smoke at start up.
If it is wet sumping a bit but not much, doesn't it pump it back to the tank in a relativly short time?


Have been pretty aggressive with the running in. Got on the bike right after first start up, no idling, have kept it between 3K and 4K most of the time. Have a few nice low hills close by so have been keeping a load on it and staying off freeways.

After all the surfacing, head work, new studs and bolts, rings,and copper spray-A-gasket it is just a bit disheartening to still have a major oil problem like this.
The only thing I didn't do was put a sealant under the washers and bolt heads.

One more question, will I mess the rings up if I pull the cylinders being careful not to disturb the rings to much?

Know you guys like pics. so this is what it looked like going back together before all this started.



Again..thanks for all the help.
Roger

My opinion about pulling the cylinder is that no, you won't hurt anything by taking the cylinder off.
Just that when you pull the cylinder, DO NOT let the cylinder rest on any ring that has expanded, once the cylinder cleared any of the rings.
Maybe having two people pulling the cylinder at once, will help kill that possibility?
Up, off, and out!


You can then look to see if any ring broke. Or was broken before.
You can see if any sets of ring gaps lined up with each other, instead of staying staggered.
IF there were any marks on the rings, you might look for those, making certain they are positioned correctly?

Roger.
The pistons looks like they have been put on the wrong way..the bigger pockets (for the inlet valves)is in front(?).

Thanks Arnstein...I think its the angle of the shot, from the right rear that makes them look different.

Just went out and put my digital calipers on them and they are the same front and back. Do some pistons have a larger pocket for the intake?

when it was running was the crankcase breather working properly ?
If so there should be some oil " leaking " down onto the drive sprocket.
If the breather is blocked or broken then excessive crankcase gasses will be forced past the rings although this usually will be the same on both cylinders

Hmmm, I don't recall noticing any pocket size difference in the 9:1 Hepolites I used but anything is possible especially with after-market & high-compression pistons.

But in returning to the original oil leakage problem, I had the same leak at the same stud on the opposite side of the engine. This was some years ago but as I recall I ended up having the head & the cylinder skimmed, used a new copper head gasket (well coated with Copper-Coat....it had ALWAYS worked before!) reassembled, torqued & took it out for a ride....came back with oil leaking past the SAME stud.....Rats says I !
I pulled it apart again and found oil still leaking somehow past the gasket & ending up at the stud base whereupon pressure succeeded in blowing it up & out at the top of the stud.
At this point, my brother suggested trying a sealant he'd had good luck using: Hylomar-Blue. It's sticky, it's kinda thick, it's Blue....it WORKED! You have to be careful not to apply it too thick as you don't want it to extrude into any areas where it might not be welcome. I put a thin layer on each side of the copper gasket, left a little room for extrusion & bolted it up. Never had a problem with oil leaking from the head again. :bigt

Just my 2 cents; HTH

May be similar to what I use at the hanger on our aircraft. Has the same properties and use.



Tite Seal Sealing Compound

Hylomar is a good sealant.
It was originally developed by Rolls Royce aero engines for use in their piston engines ( late 1940s I believe). Very widely used in UK and it is available in US.
HTH

From their website:

"Hylomar® Universal Blue sealant was originally developed by Rolls-Royce Plc Aerospace Division for sealing joints in jet turbine engines. Hylomar® is a polyester-urethane based sealant that transforms from a gel-like material into a re-sealable, non-setting, non-hardening putty within minutes of application. Because it is non-setting, Hylomar® sealant offers unlimited assembly time and is resistant to vibration and thermal expansion."

Well---in the spirit of Christmas--I guess we are just about agreed on this one, Gary.
Best Wishes for the Festive Season.

Copy that. Happy holidays.