Magneto Rotor

[chrisrappl]

I have put about fifty miles on the R69S since the total restoration. Today I changed all the fluids, retorqued the heads. adjusted the valves, took up any rocker assembly float, stripped the carbs down, cleaned and reassembled them and changed my advance limit spring.

While adjusting the carbs and syncronizing them at idle and at speed, the engine started on about 1/2 kick every time. I used a vacuum gauge that gets placed over the carb intake, so the airtubes were removed. After reassembly, the engine took a few kicks to come to life and appeared to be running lean (slight exhaust popping upon decel). This doesn't make sense to me, because adding the air tubes and filter into the equation should, if anything, have caused the engine to run slightly richer. I also had a slight dead zone coming off idle.

After a ten mile ride and twenty minute break, the engine would not start. I had to pull the plugs and clean them (even though they looked fine) and then it started right up.

I had shut off the petcock a block before stopping and I did not open it when I tried to restart. I could smell raw gas as I was kicking it over. When I pulled the plugs I expected that they would be gas fouled, but they were dry.

I took great care to set the magneto and timing properly according to the Barrington manual. The points gap may be slightly wide .018? But I figured that they would close up a little as they wear.

So... I'm wondering about the strength of the spark. Is it common for the magneto rotor magnets to weaken over the years? I know that heat and vibration destroys magnets. I don't know what the spark should look like with this ignition system, but it is a fine white spark as opposed to the fat blue spark that I would like to see. The coil makes the same spark hot or cold and seems to be in good condition - no soft spots or evidence of overheating. I do have a new replacement coil that I can install, but I don't think that is the problem. Has anyone had their rotors remagnetized? If so, Where?

Even though I took up any rocker assembly end float, I still have a tick on the left side. The right side sounds great. The only other R69S that I have experience with (Rex's bike) has the same tick on the left side. Any ideas what this could be.

[TrophyMoto]

You may have a couple of thing going on there.....Try the new coil first. Make sure the advance unit is retracting.

[schrader7032]

Double check the rotor alignment...make sure it hasn't shifted on the tapered shaft. I haven't heard much about rotors losing their "charge"; I think attempts to remagetize them are so-so at best, but there might be places that could try it. Definitely try the new coil, although the typical failure mode for a coil is difficulty starting hot but OK starting when cold.

Be sure you don't move the magneto body in order to adjust the magneto timing. Doing that changes the ignition timing. Aligning the magneto is done by popping it off the taper and placing it back on in the proper location, checking the v-notch in the magneto body.

Don't worry about the gap so much...it just needs to be in a range of say 0.012 to 0.022. The gap or dwell for a 2-cylinder bike is relatively unimportant. As long as the gap is in the range and you can get the engine to time correctly at idle and advance, you're fine. If you try a specific gap, say 0.016 and run out of rotation on the points plate to get it timed, you need to change the gap so that you an get back into adjustment range. A small gap adjustment makes a big change in rotation on the points plate.

As for the ticking sounds, that may just be how it's supposed to sound for that side. You're dealing with a collection of parts and they may just have a particular resonance. I have some simillar on my /7...I finally don't worry about it now after 50K miles.

[sonofrust]

Maybe your problem is fuel related. Was the bike running well before you took apart the carbs? Why are you taking them apart after only 50 miles? If the bike ran well with the vacuum gauge attached and poorly after hooking up the air cleaner, maybe there is something going on there. These bike are always leaking fumes somewhere, so the raw gas smell may not be an indicator of much. Do you have clear filters in the gas lines so you know gas is flowing to each side? If you run the bike with the petcock closed and then try to restart later, I would open it back up first and crack the throttle while trying to restart. With my bike, if i flood it a bit, i just hold the throttle wide open and kick in through a few times and I get at least a sputter. Also, I never clean plugs anymore on the /2, I just replace with new, as the plugs are fairly cheap. The only reason I turn the valve off sometimes before turning off the bike is so the carbs don't drip in the garage. On one of my bikes, it starts to sputter less than a minute after turning off the valve, on the other, I can ride a long way. In trying to establish your starting routine, have you ever fouled the plugs with too much gas or tickled the carbs to the point where the tops get wet? Maybe you have a gas/air issue rather than electrical. As far as the ticking goes, I don't obsess on this too much. I try to listen for noticeable changes, though. Good luck!

[chrisrappl]

The reason that I disassembled and cleaned the carbs after only 50 miles was because I could not get the engine to slow or stumble while backing out the air mixture screw.

Both carbs act the same, so I started at two turns out from lightly seated, working one cylinder at a time I turned the screws in until the engine slowed, backed them out 1/2 turn and locked them in place. The bike starts and runs fine and the plugs look good. I don't have that lean dead spot coming off idle, so I'm a happy camper.

I did remove the rocker assemblies, checked for both excessive and inadequate end float, made sure that the washers had not worn unevenly, reassembled, torqued and adjusted everything, and again, I'm a happy camper. THANKS CHRIS BETJEMANN for your help!

I took the bike out for a 40+ mile ride today and I'm still smiling.

I think that everything is adjusted and sync'd properly. If the bike doesn't start on one kick now, it will only be because I don't know what it wants. But I'll learn.

I did learn something valuable today that I'd like to share with the members of this forum. Barrington Motor Works installs remagnetized magneto rotors in all of their restorations and serviced bikes. The remagnetized rotors improve both starting and low speed running. The cost of a remagnetized rotor is $45 plus shipping with the exchange of a rotor with a good seal surface and notch in the nose for the advancer.

I will take advantage of this service if I have any further problems. If not, I will definitely do it when it is time for the next major tune-up.

Thanks to everyone who has helped.

[sonofrust]

The info. on the magneto rotor is good to know. A few years ago, I rebuilt a few old stationary gas engines that used primitive magnetos. I wound up having to get each one remagnetized and that solved all of my ignition problems. The price of this /2 magneto rotor exchange service seems quite reasonable as well. Vech's notes on aligning the magneto rotor and ignoring some of the older procedures for timing outlined in books like the Clymer was well worth the read. Getting a good look at the position of the notch and taking the time to pull the rotor to make sure it is set up spot on made a dramatic difference in my starting routine for one of my bikes. it's great that there is such fantastic advice floating around, and accessible assistance through some of the top-notch parts vendors and enthusiast forums as well. I wish this kind of information exchange was around when I started fiddling with bikes and cars over 30 years ago..

[jeff dean]

I had a helluva time kick starting my R69S:



The first advice when it starts cold but is a bastard when its hot is to get a new coil. But mine was an SOB to start any time.

Tim Stafford recommended a rebuilt magneto rotor. When that was installed, my R69S had a new, eager personality. Now it starts.

BTW: I have never had a problem starting my R60/2's.