Leaky seals and wandering sparks.

[Sunbeem]

Something's going on with the RS, and if anyone can shed any light I'd be grateful.

About a thousand miles back, I felt the engine wasn't happy, and checking the timing with a dodgy light, it was at the position appropriate for single plug heads, while mine is double plugged. I retarded things as best I could with the light, to the recommended position, and the engine ran in a much more relaxed manner - so I was happy.

Shortly after, I noticed the slight seepage of oil from the barrel/case joint was getting worse, with a clean line visible all round the joint, as if the oil was being blown away from the immediate area.
I retorqued the heads, (albeit with a spring balance one foot away from the nut), and reset the valve tappets, and that seemed to do the trick for a few hundred miles. Some studs started turning as the pull passed the 10ft lb mark, most were around 20. All set to 26.

As the plugs get very oily, and need frequent cleaning, I wanted to get the mixture as lean as reasonably possible.
I think the needles will be worn, but I'm not sure if it's enough to justify dropping them a notch, or if that would work, but I set the idle jets leaner, so it just pops slightly if I overrun downhill in second gear. I plan to check the needles when I've read up on the carbs, which I've yet to open.

This all seemed to have been successful, until the familiar feeling of "hardness" returned gradually, as if the engine is too advanced again, and the leak is returning as before.
The bike has electronic ignition, and the sensor which revolves where the points used to be concerns me a bit, as the end of the shaft it fits on was seen to be in rather poor shape when I changed the timing chain. However, it doesn't feel loose, and I assume any movement would retard the ignition, while mine seems to have found a way of advancing itself ...?
I've never changed the paste under the box that sits under the frame's rear top tube, so that's on my list.
So I'm wondering if the engine studs are pulling out due to the timing advancing itself somehow, or if the timing is OK, and the harsh feel is due to the tappet gaps altering as the studs pull out ...

I can't borrow the timing light again, as the owner has lost it, and finding another may take a while, but I understand there is no other way of timing the spark ?
And if the studs are pulling out, does that involve sending the cases to a machine shop, or can it be done by a short sighted botcher with a few hand tools ?
The engine is a '78 so there may have been other ssb's there before this one.

Suggestions, derision, flowers etc, all welcome,

Sunbeem.

[Garnet]

Sounds like you have a Dyna ignition. The rotor on the end of the cam has a habit of slipping, causing the timing to change. Usually it slips to a retarded position rather than advanced though. It has been a real long time since I had a Dyna, and it wasn't on a BMW, but if my memory is correct (highly suspect), there is a set screw holding the rotor in place. It needs a drop of blue threadlocker on it.

[ME 109]

Sorry I can't help much Sunbeem, 81-84 is my preferred period of ignorance.

[Sunbeem]

Thanks Garnet, I was thinking the rotor may be at fault, as I can't think of anywhere else that the timing could slip, and remember having some bother with it last time in. (Unfortunately I've lost the relevant brain cells since.)
The direction of the change is counter-intuitive, but still worth a good gaze in that neck of the woods. I may have filed the shaft end back to shape and created a gap which needs a bit of filling, so I'm not only depending on the tightness of the screw.

Sunbeem

PS. No worries Jeff, this one falls neatly within my area of ignorance, (slipped right through me fingers ...).

[enigmaT120]

I don't think the engine studs nor the oil leak are related to the timing drift. There are kits for helicoiling the stud holes, and a special tool to make sure you do it right. I would probably have a local BMW guru do it if it happened to me. Oily plugs sounds bad, as does trying to make the air-fuel mix lean in order to compensate. Could you have worn valves or rings?

[Deleted User 62]

Something's going on with the RS, and if anyone can shed any light I'd be grateful.

About a thousand miles back, I felt the engine wasn't happy, and checking the timing with a dodgy light, it was at the position appropriate for single plug heads, while mine is double plugged. I retarded things as best I could with the light, to the recommended position, and the engine ran in a much more relaxed manner - so I was happy.

Shortly after, I noticed the slight seepage of oil from the barrel/case joint was getting worse, with a clean line visible all round the joint, as if the oil was being blown away from the immediate area.
I retorqued the heads, (albeit with a spring balance one foot away from the nut), and reset the valve tappets, and that seemed to do the trick for a few hundred miles. Some studs started turning as the pull passed the 10ft lb mark, most were around 20. All set to 26.

As the plugs get very oily, and need frequent cleaning, I wanted to get the mixture as lean as reasonably possible.
I think the needles will be worn, but I'm not sure if it's enough to justify dropping them a notch, or if that would work, but I set the idle jets leaner, so it just pops slightly if I overrun downhill in second gear. I plan to check the needles when I've read up on the carbs, which I've yet to open.

This all seemed to have been successful, until the familiar feeling of "hardness" returned gradually, as if the engine is too advanced again, and the leak is returning as before.
The bike has electronic ignition, and the sensor which revolves where the points used to be concerns me a bit, as the end of the shaft it fits on was seen to be in rather poor shape when I changed the timing chain. However, it doesn't feel loose, and I assume any movement would retard the ignition, while mine seems to have found a way of advancing itself ...?
I've never changed the paste under the box that sits under the frame's rear top tube, so that's on my list.
So I'm wondering if the engine studs are pulling out due to the timing advancing itself somehow, or if the timing is OK, and the harsh feel is due to the tappet gaps altering as the studs pull out ...

I can't borrow the timing light again, as the owner has lost it, and finding another may take a while, but I understand there is no other way of timing the spark ?
And if the studs are pulling out, does that involve sending the cases to a machine shop, or can it be done by a short sighted botcher with a few hand tools ?
The engine is a '78 so there may have been other ssb's there before this one.

Suggestions, derision, flowers etc, all welcome,

Sunbeem.

Sun, as I understand it, dual plugging is for reduction of pinking at low rpms, so the timing shouldn't need retardation. Oily plugs has nothing to do with mixture, that oil is coming from somewhere. Do your crankcase breather tubes go into both carb spigots? It could be your breather has failed (broken or weak spring) but more likely your rings are shot and the blowby is dumping oil into the carbs, hence the oily plugs. Popping on deceleration is too lean, I'd put it back where it was. Remember, these type carbs are semi self adjusting, it's timing, valves, coils, etc that change over time. You can check your timing with a static timing light, just a bulb with a wire. Clip wire to contact coming from condenser, ground light bulb, turn ignition on, but don't start bike, then turn engine with allen in alternator rotor and see where it comes on in timing window. I'm not sure if your description of the alternate torque wrench will work. If I were you, I'd spring for a simple beam type torque wrench, or beg borrow steal one. When torquing oily connectors, you should use less than spec torque, maybe 25ft/lbs, but if they indeed did start turning at 20ft/lbs, well you've got bigger fish to fry, so to speak. These guys sell a tool for fixing pulled studs, but it's very pricey: http://www.cycleworks.com/ edited to add: excessive blowby, from worn rings might increase seepage from seals/ seams that were already on their way out.

[Major Softie]

I'm just glad this title was talking about your motorcycle...

[Sunbeem]

I'm not sure if the oil is coming past the rings, or through the valve guides, but it makes it tricky to see what the mixture's like on the plugs. Now that I've got a weatherproof shelter over the bike, I can contemplate addressing the oil issue, I've had to put up with it for a while. Hence tuning the mixture on the hoof.
Supposedly the cylinders were rebored by the PO, when he had it dual-plugged. I suppose I won't know 'til I look, but since the bike runs so nicely, I don't really want to rush in.
There are various ideas concerning timing, I've gone with the school of thought which recommends retarding from standard, as the flame fronts achieve their objective faster than a single plug. Certainly that seems to work for me.
Following Garnet's suggestion I had a look, and found that the rotating sensor was rock solid on the shaft.
The Phillips screws which retain the timing backplate however, were manky in the extreme, and obscured by the disc holding the sensors, offsetting the proffered screwdriver. A case for Allen screws I think. My suspicions centred around the timing marks, since nothing lined up amongst the proliferation of scratches to be found on the relevant surfaces.
Marks around the retaining screwheads witnessed to movement. I reckon the thing needs a good clean when I change the screws.
I reset the timing to the mark I used last time, which involved retarding it by about 3 or 4 mm against the mark, gave the studs a careful nudge, reset the tappets, and fired up.
And we were back to normal.
I took her out for a relaxed canter, and everything was fine, so a good fettle is required to secure the backplate more effectively.
I can see that too much advance could put a strain on the studs, so now it is under control, I'm hoping things will stay as they are ...

Sunbeem.