Help Troubleshoot

[Stan_R80/7]

I meant, is there spark when this occurrence happens, and you can't get it started? Issues with the ignitor, bean can, or especially ignition switch can appear and disappear seemingly randomly. It makes no difference if you had successfully adjusted timing recently, where the failure event is somewhat random. If you take an inline spark checker with you, you can check for spark right after it dies and won't start. Then you can eliminate, or focus on, your electrics.

+1

F.A.S.T - fuel, air, spark ,timing

I carry spark thread extenders for balancing the carbs, but they work great to check for spark also. The next time it dies, check for spark. If you have spark, then you have F.A.T remaining.

[manitou_commando]

Update!

Took the advice of someone who commented and adjusted the valves. Removed left valve cover first and the nut on the top-front stud was loose. This seemed like a dead giveaway that one or both of the left side valves may tend to be out of whack.
Loosened and torqued the head, adjusted the valves and put the valve cover back on. Checked the right side while I was at it. Perfect in there.
Stared right up and didn't die in 1/2 mile. However, I am not at all certain that I am any closer to having located the source of the mystery stalling.

Tomorrow morning will be a better indicator. I will keep you all posted.
Hasta

[bikerfish1100]

not wanting to rain on your parade, but a loose valve cover nut has no connection to valve adjustment or head torque status. did you happen to check your valves before you loosened things up? (sounds like answer would be no).
hope you're lucky.

[manitou_commando]

Bikerfish,

I didn't say that the valve cover was loose. Do you ordinarily jump to conclusions before reading closely?
Thinkin' that answer is Yes.

Thanks.

[bikerfish1100]

Rick- apparently i misread this statement to think you were referring to the valve cover stud.. "Removed left valve cover first and the nut on the top-front stud was loose". If you meant one of the head bolts was loose, then your actions were correct. but your attitude is a bit lame, especially given that i was among those recommending that your valves should be checked/adjusted as a first option.

[lkchris]

Just a note about ignition timing ...

... like wheel alignment on a car, you never need to do it.

It's in fact physically impossible for your RS' ignition timing to "go out" and/or need checking or adjusting unless bearings associated with the system are worn and it's wobbling. In that case, you need new parts, as there's no "adjusting" to fix this.

Of course timing may be out if it was done incorrectly last time, but that's pretty silly, isn't it? "Done incorrectly" obviously includes failure to tighten it down, but then if that happened what's to say it only moved "a little bit" from the correct postion? If it's loose it could just as easily move so much the engine wouldn't run. These concepts are simply silly.

I know these engines are getting older and older, but I still think the first thing to check is always valve adjustment. Chances of just about any problem being "timing" are about zilch. In the desert southwest it's always good to check for vacuum leaks related to the fact German rubber isn't so great with this sort of climate.

[bikerfish1100]

Kent- don't forget that timing can/will go out if points gap is incorrect, as points wear, or as points rubbing block wears down.

[Stan_R80/7]

Valve train timing is affected by valve clearance. If the valves are too loose then the valve timing changes. Stretching of the timing chain affects both the valve timing and ignition timing. I think Timing it is last in the F.A.S.T. acronym to a.) make the acronym easier to remember and b.) it is generally more difficult to check than the fuel, air, and spark when troubleshooting. YMMV.

[manitou_commando]

Update: After following sage advice mentioned herein, the valves were adjusted, carbs balanced and the timing was check, though not much needed there. More of a verification that timing is within range.

Upon turning the ignition key, the gen, oil, and neutral lights come on. It starts. Then after 1/2 mile it still dies. So we are onto the assertion of others that this is electrical in nature.
Wen I switch off the key in the ignition, the oil light may or may relight though the other two still do. The starter is able to churn away. Benzene is in the bowls.
As this is an electronic ignition, what is the recommended way to check for spark without damaging the ignition? I figure that working backward from the plugs through the ignition circuit (should no spark be extant) then it may be a simpler process.

Thanks,

Rick

[Stan_R80/7]

I keep an official BMW tool kit with my airhead. This kit includes a socket to remove the spark plug. If my airhead died on the road (and I did not have my carb balancing tool) I would remove the plugs from the head, reattach them to the plug wires, and rest them on the cylinders to test for spark. The plugs should not be 'torqued' to use the BMW socket but instead tightened using the tool to allow plug removal when the bike stops.

It sounds like an electronic ignition problem that could be from a defective hall effect sensor. But, testing for spark the next time it dies is needed to be certain. Good luck!

[happy wanderer]

I made one of these from an old spark plug and a spring paper clip and keep it in the tool bucket under the seat. Take one spring out and bend it so it clamps onto the plug nice and tight and fit it back into the clip like so.



Clamp it to a cooling fin like so and watch the electrode for spark. Or not...



When you have a no spark condition almost the last thing that goes wrong is the plugs themselves so unless I suspect a bad spark plug I don't bother removing them unless this test fails.

[lmo1131]

Thanks for posting this. It enlightened me in two ways.

1) THAT is the cleverest-est way to hold a spark plug I've seen to date.

2) I recently posted that I replaced the OEM BERU spark plug caps on my '73 /5. I replaced them with new parts from MAX without thinking about, or understanding that post 1979 they were 5Ω.