Ignition Timing trouble 1978 r100s w/ Dyna II

[5446dailey]

I recently moved from 6,500 feet (N. Lake Tahoe, CA) to sea level (Morro Bay, CA). My 1978 r100s would always run very rough with a high idle at sea level. Shortly after moving I bought a twin-max balancer and got the idle mixture and sync just about right. I left the mixture a little rich just to be on the safe side.

For the past six months or so, since I moved my bike's been running really hot. I also bought a timing light, thinking that the overheating was caused by the ignition timing being too advanced.

The F (full advance) mark shows up at about 4100-4200 rpm, but no mark registers at idle 1000-1200rpm. Also the Gen light comes on when the rpm drops to or below 1050.

The manual says that with points the idle should be set at 700-1000 rpm, but with an electronic ignition it should be set between 1000-1100rpm. Is this the reason no mark registers at idle?

Can I do a static timing adjustment with a normal timing light from the auto parts store or is the flywheel marked for a 700rpm idle?

I know there is a special BMW light box, but I don't have the right connector or the money for that part.

I kind of just want to convert it back to points.

Any feedback would be greatly appreciated.

Thanks,

Brent

[toooldtocare]

A guess here. My 78 R100RS has a Dyna III and a lightened flywheel. San Jose BMW did the work in the 80s. When they lightened the flywheel, they cut off the timing mark for the static timing and applied a dab of red paint to the flat surface of the flywheel. Hard to see, but it is there. For TDC, which was also cut off, they applied a dab of white paint. Does your bike have an aftermarket lightened flywheel?

Also, you can remove the plugs but leave them connected to the wires and lay them on the cylinders. Then slowly turn the engine using the rear wheel in 5th gear. There is enough spark generated to create a snap which can be heard. This is how I timed my bike recently because I could not see the red dot while the engine was running.

[20774]

I have the Dyna III on my /7 and haven't had any timing problems with it. I also have a Twin Max.

I've not heard that the RPM for idle should be different for points versus an electronic ignition. IMO, 700 to 900 is too slowly regardless. Shoot for 1000 to 1100 for idle RPM.

Over 4000 at full advance is definitely too high. It should reach full advance around 3000-3200 RPM. When using the timing light, do you see a single full advanced symbol in the timing window? You should, if you've got the two pickups on the Dyna set right.

As previously suggested, pulling the plug, or better yet, just pulling the wire and sticking in a spare plug while the plugs threads are in direct contact with the fins might be easier. Of course, if you leave the plug in, it will be more difficult to rotate the engine using the rear wheel in 5th gear.

Remember that the Dyna III is nothing more than a switch just as the old points were a switch. The Dyna allows independent adjustment of each cylinder's firing point. Just as the points made and broke the current flow to the coils, so does the Dyna. You can also monitor the ground signal at the coil where the Dyna attaches. When the "points" open, you will see the loss of ground at the coil.

If you'll recall, the Dyna has the separate adjustments for each pickup head, but the whole plate can be rotated to shift the firing at idle back to where it should be. HTH...

[5446dailey]

The electronic ignition is actually a Boyer Branson Type-Mk3. I don't know why I was thinking Dyna II. Maybe it was from all the snowbum reading I was doing. All the fly wheel markings are original S (Static) F (Full Advance) and OT (Top Dead Center). Yes, the F (Full advance) mark makes a single image. Can I still do a static timing adjustment by pulling the plugs, grounding them to the fins and rotating the engine like you said if I have an original flywheel?

Also, I have a really hard time shifting gears and finding fifth gear when the bike is turned off. I actually don't think I've ever found fifth gear without the bike running.

Would it also work to rotate the crank shaft through the alternator with an allen wrench, as long as the plugs are pulled? This is how I do my valve adjustments.

Thanks,

Brent

[toooldtocare]

The electronic ignition is actually a Boyer Branson Type-Mk3. I don't know why I was thinking Dyna II. Maybe it was from all the snowbum reading I was doing. All the fly wheel markings are original S (Static) F (Full Advance) and OT (Top Dead Center). Yes, the F (Full advance) mark makes a single image. Can I still do a static timing adjustment by pulling the plugs, grounding them to the fins and rotating the engine like you said if I have an original flywheel?

Also, I have a really hard time shifting gears and finding fifth gear when the bike is turned off. I actually don't think I've ever found fifth gear without the bike running.

Would it also work to rotate the crank shaft through the alternator with an allen wrench, as long as the plugs are pulled? This is how I do my valve adjustments.

Thanks,

Brent
I do not know anything about the Boyer Ignition, but I think that it would work the same way as a Dyna. My current bike (78RS) has the Dyna. A few years ago I had an R90S that had an aftermarket ignition, I do not know the name. I had several problems with it, keeping it adjusted, etc. It had no mechanical advance, but relied on the black box circuit to provide the advance. I removed it and reinstalled the points and mechanical advance. They worked ok for me, but I then sold the bike and the new owner installed a Dyna. He said that it made a big difference.

Yes, you can turn the engine with the alternator. I just use the rear wheel because it is easier than removing the front cover. Remember, unhook the battery before you remove it and only hook it up after it is off to prevent an accident short.

While in there I would look at the advance unit to see if it is mechanical, or has it been removed and a PC board with two pickups installed over a rotating disc instead. This is what my R90S had when I got it and I was not impressed. However, my Dyna has been on my current bike since 85, although it has not covered many miles since then. It has been perfect in my knowledge from the previous owner. It uses two pickups, but the factory mechanical advance. Good luck.

[20774]

Would it also work to rotate the crank shaft through the alternator with an allen wrench, as long as the plugs are pulled? This is how I do my valve adjustments.

Pulling the plugs puts much less strain on that allen bolt and trying to turn the engine. I used to use the allen bolt, but find using the rear wheel easier.

As for getting the tranny in 5th gear, I find have to work the wheel around as I go through the dry shifting. I'm sure 4th gear would work too, just a bit less mechanical advantage. You might want to revisit your clutch cable adjustments...that might be contributing to the problem. The "Tom Cutter" method of adjustment has been posted in this forum...works like "buttah".

[beemerguru]

Just a thought about running hot..

Valves have been checked?

Were main jets changed with the move?

Oil level good?

Why do you think it's running hot?

Boyers or Dyana are ususally fit and forget. Nothing really to go wrong with them unless someone starts messing with them.

[85K100LT]

Just a thought about running hot..

Valves have been checked?

Were main jets changed with the move?

Oil level good?

Why do you think it's running hot?

Boyers or Dyana are ususally fit and forget. Nothing really to go wrong with them unless someone starts messing with them.

Yes what is running hot is this a seat on the pants feeling or have you checked engine temp with a infrared temp guage. My R75 runs approx 300 degrees at the spark plug normal as far as I can tell. oil temp in around 200 to 250 degrees with a oil temp dipstick.

[5446dailey]

I have not measured the temperature of the engine or the oil. On rides 10-20 Hwy. miles, valve covers are too hot to touch and I can see heat waves on warm days when I park in the sun. A lot hotter than it used to run at higher elevation.

Valve clearance is good, oil level is good, but main jets have not been changed. I have been meaning to rebuild the carbs when I can afford a the rebuild kit. I want new diaphragms, jets, needles, floats, float pins, in-line filters, gaskets and o-rings, but I'm trying to figure out the most economical way to do it. Also, one of the arms that holds the float pin is broken on the left side carb. A BMW mechanic in San Francisco epoxied for me, but I'm not sure if I want to spend the money rebuilding a broken carb.

Should I have a different size main jet a sea level? I bought the bike from a dealer in Ventura which is where it was originally purchased (also at sea level).

[Polarbear]

Boyers are junk! I've taken a few Boyers out of BMWs and put Dyna's in and solved a lot of problems right there...I think they are English made, so think "Lucas" of old and you have a good answer:).....I don't know where Dyna's are made, so be it...Randy:thumb

[toooldtocare]

Should I have a different size main jet a sea level? I bought the bike from a dealer in Ventura which is where it was originally purchased (also at sea level).

Unless you can measure the temperature there is no way to know it it is running hot or now. From BMW factory service manual for the /7 series:
R60/7 gets 140 main jets, R75/7 gets 145 jets, R80/7 gets 145 jets, R100/7 gets 150 jets, R100S gets 170 jets, R100RS gets 170 jets.

I used to live in West Texas where it was very dry and hot. I bought a used 95 R100RT with only three thousand miles on it. The previous owner thought it was running hot and installed bigger jets. I added a dipstick oil temperature gauge and saw that average temperature was about 230.

When I got the bike it only got 35 mpg and could barely hit 80 mph. I replaced the jets with factor ones (smaller) and the gas mileage jumped to 45 and the top speed was about 105 with both my wife and me aboard. Funny thing, the average temperature stayed at about 230 max.

I do not know what jets are in yours, but I would try the factory jets first.

[CellarRat]

Boyer instructions are on line. Google Boyer Ignition and you will find a listing of all instruction sheets; scroll to find the one that suits the specific BMW. There are several variations, including twin - plug bikes.

For a standard 78, the URL is http://www.boyerbransden.com/pdf/KIT00286__BOX00237_.pdf

Note that advanced timing is to be set at 4000 rpm.

I've fitted many Boyer ignitions to Airheads, and NEVER had a problem unit.

In my experience, Boyers have a slightly delayed advance curve from the stock points, which was helpful in dealing with machines that suffered pre-ignition on acceleration.