one thing I am going to try before I go down this line is to change the oil and filter and double triple check the oil level. I usually run my bike just above the max line. I was wondering if it was being pushed past the rings because of being slightly overfilled? trying to eliminate everything!
You could just drain down to the min oil level to eliminate over filling, I believe some ss's had the max level decreased, there was a factory fitted sticker over the max mark on the casting, early 90's. This may apply to yours.
I stumbled across that issue while researching my "issue". must admit its something I hadn't seen before as ive always run my 900 a little over the max level mark which on my bike is at the bottom of the sight glass. Not really had an issue in that respect. That said, im tring to iliminate everything before i pull the motor!
Here is my level marker..... the level is showing a little high as the bike is sat on a paddock stand tilted slightly over to the right. Having topped the oil up and triple checked the levels, I started the beast which ran and ticked over fine however as you can see from the photos oil is obviously still entering the combustion chamber and being pushed out the exhaust. There is a distinct amount of unburnt wet oil being pushed from the exhaust joint which is spattering over the frame. On another note, I cleaned the exhaust pipes out with meths before startup so its not "residual" oil. This now leaves me with no option but to motor out (again) and check everything relating to the rear cylinder and head.... my rather large gut feeling is rings or bore and on that note, if it comes to it anyone know where I can get the bore re nikasiled or a replacement cylinder? This is seriously pissing me off, I just want to ride the damn thing
That's the same marker as on my 907 although I think it is slightly higher on it, level with the upper of the 2 cast in lines. I usually fill it to ½ to ⅔ up the sight glass with no issues. I'd be surprised if oil level is the cause of your problem.
Thats exactly where i have run this bike, between the two cast marks. I "reset" the level in order to eliminate any possible excess pressure caused by overfilling to no avail. Alas its engine out nothings ever simple!
If you've got an air compressor I'd be tempted to do a leak down test rather than relying on the compression test.
Right folks, back again with this damn oil leak...... An hour this morning separated the frame from the engine. I popped the vertical head off to be confronted with the following. I took the head off VERY carefully so as not to disturb any telltales in relation to the oil path. What is clear is that oil is getting into the combustion chamber and being fired out the exhaust port, quite a bit of it from the looks. In the right of the cylinder looking forward are the oil feed with the green o ring and the two oil returns with the black o rings. There is no evidence of oil leaks around these o rings or the oil feed. On the rear mating face of the cylinder, there are traces of oil where it appears that oil is being forced between the joint under pressure. The head itself appears normal with the exception of being a little coked up because of the rich running. I took the head to my table in the back garden in the sunshine where I removed the inspection covers and all appears normal. The seals are in as new condition, which is to be expected as the valve guides and seats were replaced in this head. just to make sure, I flipped the head over and filled the combustion chamber with meths then went and made a brew. Zero fluid loss so all is well in the head dept. So its back to the cylinder. The bores look smooth without any noticeable wear or other marks, in addition there has not been any metal fragments in the oil suggesting any ring breakup or the like. I am looking for some suggestion as to what I might be missing in relation to this problem. It seems apparent that the oil is getting into the chamber past the piston which may suggest a stuck or defective oil ring, although at 143 PSi on the compression, this doesn't feel right. Anyone help?
barrel off and piston out. Its an Arias HH8935. No apparent damage to the rings all of which are free moving. there is a tiny amount of wear on the piston skirts which corresponds to the "marks" if you can call them that, on the bores.
although it's hard to see as still coated in oil from dismantling, the two corresponding faces on head and barrel required to seal the combustion chamber don't appear to show evidence of sealing as per usual, so despite healthy compression reading on that bore, it doesn't look to be oil-tight to me.
Hi Chris, this is whats causing my consternation, There is zero evidence of a leak at the o ring seals. If there was I would assume the oil leak to be on the outside of the cylinder between the head and barrel and nothing in the combustion chamber. My feeling is that the oil on the mating faces has been forced out of the barrel under pressure together with the quantity coming from the exhaust port. Im not entirely convinced its anything to do with the "outside " of the oil circuit, i.e the o ring seals etc. Question, If it were anything to do with the cranckcase breather, wouldn't both cylinders be blowing oil?
yes, both cylinders would be affected by a severely blocked crankcase breather but it's unlikely and would be unusual to affect combustion chambers to that degree. If it did happen, results wouldn't necessarily be identical in both cylinders is the short answer. Did you check breather gauze and pipes to catch tank and air filter? If you had crankcase compression as a result of compression and/or oil ring problems then you would see oil smoke puffing from crankcase breather exit (pipe removed) on a hot engine.Were there signs of excess oil in air filter body? Just a long shot - has anyone replaced/looked at the oil pump and pressure valve prior to problems? also, is the oil gallery sleeve in troublesome bore the one that was original to the engine?
With that amount of oil in the cylinder you can't rely on the compression figures. I'd be tempted to measure the piston to cylinder, ring to land and the ring gaps and cylinder bore.
Hi Paul, to be fair, im contemplating getting another set of pistons and thinking of sending the cylinders off to Langcourts for rework, at least that will eliminate the pistons / bores which I'm beginning to think is the issue.
The other issue I’ve experienced in the past is the hole in the carb that feeds the pilot jet becoming blocked. Took ages to diagnose because the pilot jet itself was clear and I’d blown the carb out with air. I cleared it in the end by poking thin weld wire up the hole until the blockage shifted.
