I picked up the very nicely maintained '82 (which is my first BMW!!) a week ago; it seemed to run alright for the 15 minute test drive, now there is no spark at the right plug. What could cause this? I had trailored it home 600 miles; then the batt. (Yausa #Y60-N24AL-B) wouldn't turn it over or charge enough to get her running so I replaced the old battery with a sealed mainenance free 'absorbed glass matt' unit #ETX16L (from my local farm supply store,; their referance book reccomended this battery). The new battery is about 1" narrower than the other and also the battery tray. Did this new battery cause something to burn out? I suppose it could be that I broke a plug wire or plug when testing it all. The bike supposedly has about 45K miles and was nicely cared for. Thanks for any help.
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R100/RS: No spark at plug
- Thread starter Rocket
- Start date
flash412
Loose Cannon
If you have spark at one plug and not the other, then the most likely candidates for replacement are, in order: spark plug cap, spark plug wire, spark plug, coil.
BMW gets $25 (each) for those crappy, failure prone Beru caps. Get a pair of 5k Ohm NGK caps for $8 (for the PAIR). They will work great and probably never fail.
Don't anybody start posting crap about the fact the Beru are 1k and the NGK are 5K. Failed Beru caps will get up above 1 MEG before the bike starts having ignition problems. Better to have a RELIABLE 5k than a 1k which gradually increases over time until it no longer works at all. For that matter, you CAN get 1K NGK caps, they're just a bit harder to find and likely NOT stocked at your local Japanese bike shop.
BMW gets $25 (each) for those crappy, failure prone Beru caps. Get a pair of 5k Ohm NGK caps for $8 (for the PAIR). They will work great and probably never fail.
Don't anybody start posting crap about the fact the Beru are 1k and the NGK are 5K. Failed Beru caps will get up above 1 MEG before the bike starts having ignition problems. Better to have a RELIABLE 5k than a 1k which gradually increases over time until it no longer works at all. For that matter, you CAN get 1K NGK caps, they're just a bit harder to find and likely NOT stocked at your local Japanese bike shop.
First off, let's consider the simple stuff: check that the "kill" switch is in the center "run" position. I always use the kill switch to shut off the engine, then the main switch. It's possible you only turned on the main switch (on the headlight left side) and the kill switch is in OFF.
Be aware that the main switch has a "Park" position after OFF. If you leave the key in Park, it switches on the tail light--which over a period of hours can drain the battery. OK when parked along a dark road, but not OK when transporting the bike on a trailer, or parking overnight in the garage. When attempting to start the engine, first turn the main switch to ON (clockwise) not to Park.
Also, be aware that there are fuses inside the headlight shell. If you happened to short something while changing the battery, a blown fuse will prevent power from reaching the coils. When disconnecting a battery, remove the ground cable first, then the positive (red) side. When connecting, attach the positive first, then the negative ("ground") That way, if you happen to short your screwdriver to the frame, while diddling with the + side, it won't make sparks.
Did you happen to remove the front engine cover during your electrical checking? Be aware that the front cover is close enough to the diode board that it's almost impossible to remove the cover without grounding (and frying) some diodes. The drill is to detach the ground wire from either the battery terminal or transmission bolt before attempting to remove or install the front cover.
The diode board can suddenly fail on it's own, but usually you get a warning of reduced voltage. (the red light on the dash stays on) If the diode board is bad, either the alternator won't charge the battery, or the battery will discharge. If your brand new battery (you did charge it first before installing, right?) seems to be discharging, take a look at the diode board.
Did you transport the bike in the rain? It's possible the coil(s) are cracked or terminals are corroded, and water penetrated, causing shorts, opens, or reduced voltage. Inspect the coils and especially the wire connections. Clean (and grease) the bolt where the ground wires attach to the frame.
I second Flash's motion to install NGK plug caps, even if the big ugly BMW caps appear to be good. I've used NGK 500 ohm caps for years with no problems and no failures. Use a 90 degree short cap. (see your local Honda/Suzuki/UJM shop) Don't attempt to run the engine without resistor plug caps--the coils may burn out.
Noting the caution about the front cover, take a look at the ignition points, and be sure they are opening and closing correctly. I've seen points with a loose screw that allowed them to close up. No gap--no spark A closed gap can mimic a lean fuel condition.
Know that airheads are well known for weak charging systems. Try to conserve battery power, even when everything is working correctly. For instance, if you're going to do some testing with the key on, disconnect the headlight first. (I've installed switches to turn on/off both headlight and tail light)
pmdave
Be aware that the main switch has a "Park" position after OFF. If you leave the key in Park, it switches on the tail light--which over a period of hours can drain the battery. OK when parked along a dark road, but not OK when transporting the bike on a trailer, or parking overnight in the garage. When attempting to start the engine, first turn the main switch to ON (clockwise) not to Park.
Also, be aware that there are fuses inside the headlight shell. If you happened to short something while changing the battery, a blown fuse will prevent power from reaching the coils. When disconnecting a battery, remove the ground cable first, then the positive (red) side. When connecting, attach the positive first, then the negative ("ground") That way, if you happen to short your screwdriver to the frame, while diddling with the + side, it won't make sparks.
Did you happen to remove the front engine cover during your electrical checking? Be aware that the front cover is close enough to the diode board that it's almost impossible to remove the cover without grounding (and frying) some diodes. The drill is to detach the ground wire from either the battery terminal or transmission bolt before attempting to remove or install the front cover.
The diode board can suddenly fail on it's own, but usually you get a warning of reduced voltage. (the red light on the dash stays on) If the diode board is bad, either the alternator won't charge the battery, or the battery will discharge. If your brand new battery (you did charge it first before installing, right?) seems to be discharging, take a look at the diode board.
Did you transport the bike in the rain? It's possible the coil(s) are cracked or terminals are corroded, and water penetrated, causing shorts, opens, or reduced voltage. Inspect the coils and especially the wire connections. Clean (and grease) the bolt where the ground wires attach to the frame.
I second Flash's motion to install NGK plug caps, even if the big ugly BMW caps appear to be good. I've used NGK 500 ohm caps for years with no problems and no failures. Use a 90 degree short cap. (see your local Honda/Suzuki/UJM shop) Don't attempt to run the engine without resistor plug caps--the coils may burn out.
Noting the caution about the front cover, take a look at the ignition points, and be sure they are opening and closing correctly. I've seen points with a loose screw that allowed them to close up. No gap--no spark A closed gap can mimic a lean fuel condition.
Know that airheads are well known for weak charging systems. Try to conserve battery power, even when everything is working correctly. For instance, if you're going to do some testing with the key on, disconnect the headlight first. (I've installed switches to turn on/off both headlight and tail light)
pmdave
Thanks much for the input. Problenm isn't yet fixed but I'm crossing out possibilities. I did transport during a 2 hour 4" down pour so I cleaned and greased the coils and connections. The kill switch was not on 'run'; main switch was not in 'park'; new battery is still at 12.3v; bike does have a headlight off switch that I use. Though I have not gotten into fuses inside headlight or under front cover for points or diode board I will tomorrow. as well as get the wires and plugs as you mentioned. Any advice on the plugs type?
Thanks again.
Thanks again.
lkchris
Active member
The 1982 R100RS (no slash) does indeed have two coils but both fire simultaneously and there is one waste spark in one or the other cylinder per revolution.
BMW wires are 5K ohms.
With BMW's electronic ignition, trying to fire a plug without the plug or wire grounded will ruin the coil. And, there's a warning decal on your fender that the capacity of the electronic ignition system is enough to be fatal.
BMW wires are 5K ohms.
With BMW's electronic ignition, trying to fire a plug without the plug or wire grounded will ruin the coil. And, there's a warning decal on your fender that the capacity of the electronic ignition system is enough to be fatal.
The spark now seems to be strong and motor runs smooth. I replaced wires and plugs and cleaned all connections. The $ for 5K wires/ends was $10 compared with BMW's $68!! Tomorrow I'll get into the points etc. The bike really runs nice; though the guages really bounce around at speed, any thoughts?
When I tested the plugs I luckily did ground them out on the frame; thanks.
When I tested the plugs I luckily did ground them out on the frame; thanks.
