R65 Ignition Settings

[sdmdc]

I have a '79 R65 which is supposed to burn 93 Octane, if I read the book right.  Does anyone have a suggestion for ignition settings (dwell, timing)when using 91 Octane?  Thanks - Malcolm

[Rob Valdez 79 R65]

I read (on Boxerworks?) recently that octane is calculated differently now that it does not contain lead, so the information in your rider's manual may be out-of-date.

I have a '79 with a 1980 engine in it (no real differences).  With both engines, I have always used "regular" (lowest grade), and never had a detonation problem.   I don't even know the octane number on the pump without stopping and looking.  I also have no idea what my dwell angle is.  The bike runs - seemingly happily.

[sdmdc]

Thanks for the input.

The owners manual and my more recent repair manual call for 98 octane using the Research method to determine octane and 88 using the Motor method.  Here in the States, an average number is what is posted at the pumps.  That's (R+M)/2 or, in this case, 93 octane.

My question was prompted not so much because of ping but because it runs poorly at low speeds unless it's really been run hard.  It's the original engine with only 2300 miles on it but it sat outside for 22 years.  I've gone through the carbs and the ignition and reset the valves.  The compression is excellent.  I use a mechanical manometer to balance the carbs.  I have not replaced the points or coils so I may have to look further into the ignition.  I also had an issue with bad threads in one plug hole that could not be solved with a standard insert so I fabricated one.  Because it has a shoulder on it, that plug sits out of the head a little farther than normal.  I've tried it with and without a seal.  I plan to replace the insert with a flush one heli-arced in place.

So, I have more places to look and will leave the timing and dwell where the book says.  In the meantime it's drivable but not the smooth machine it should be.

Thanks again,
Malcolm

[Justin B.]

Octane will have no affect on how it runs, other than pinging.  Time with timing light at 3500 RPM (or higher) for the "Z" mark in the timing window.  If it doesn't ping then you're good to go.  If it pings then go up a grade, try a different brand of gas, or knock it back a degree or two.

It's possible that maybe whoever "tuned" up the bike last retarded the timing so that it could run on regular, that would decrease performance and could affect idle quality and low speed running.  

If it has sat outside for that long it sounds that you just need to do a complete tuneup - valve clearance, points adjust, plugs, timing, carb sync, etc...  You still could have carb issues as well as maybe degraded spark plug wires.  Without starting off with a known baseline for the basic tune then you are just chasing your tail in the dark!