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R100 Monolever (Classic) won't start after washing

brainep

Brain
Ok...need a little help here please. Hopefully you more experienced wrench-turners can provide some pointers. At the risk of sounding really dumb I am going to ask your advice with some issues I am having today with my '91 R100 Monolever/Classic. The bike has run perfectly since I bought it earlier this year. It has always been properly taken care of and all the maintenance is up to date. A complete service was done by a BMW shop in March. I rode it for more than 2,000 trouble-free miles in the past month.

Earlier today I washed the bike thoroughly and air dried it with the blower part of my shop-vac. When I went to crank it up so I could ride for a little while, all the lights came on and it would crank normally but would not start. I checked the fuel level and all the other normal things, tried to start it again but nothing other than the engine/starter just turning over. I then pulled each plug and while cranking touched the cylinder to verify I was getting spark....check. Towards the end of my spark check I got a loud BANG that surprised me....a backfire.

Frustrated (and worried I was going to screw something up) I pushed the bike back in the garage, and since I wasn't going to ride, I poured a beer. A little while later (20 minutes) I turned the key and the neutral light would now not come on....only the red GEN light. The key was on and I was not trying to crank the bike and about 10 seconds later the bike backfired again.

I fear I got water in somewhere I didn't want it to be. I removed the gas tank and will let it sit overnight.

Any suggestions on what to check tomorrow?


Thanks in advance for any advice.

All the best,
Brian

R100 Monolever ('91)
R90/6 ('76)
 
Hmm, the backfire you are hearing...is it coming from the exhaust pipe or just a small 'puff' before you crank it? If its the latter, don't worry about it.

WD-40 is your friend (WD stands for Water Devaporator or some such thing)
I'd squirt some WD-40 into the key hole, around the kill switch and probably the coil.

Drop the bowls on the carbs and check for water. Also before you crank it tomorrow, pull the dipstick and look at the fluid. If its milky, drain the oil (you've got water in it and its just not worth the risk).

When you pulled the plugs, and cranked it to check spark did you notice any water coming out? Are the plug tips dry or wet? If they are wet, clean them (carb cleaner, etc.).

Make sure both ends of each spark plug are dry and spray a little WD-40 in there too.

Pull your air filter off and check it for dampness.

If you don't have a fairing, maybe you got water inside the headlight bucket (where the main wiring harness is).

If you want to pull the front cover off, DISCONNECT the BATTERY first so you don't short the diode board out. If you can leave that off for a day, things that may have gotten wet in there will dry out...including the points. WD-40 again. Replace the cover, reconnect the battery and try it.

Oh yeah, after you pushed it back into the garage (did you push with the clutch lever squeezed???), the nuetral light won't come on if you left it in gear, but the gen light will. I am, of course assuming you always start with the clutch cable squeezed in for safety.

Good luck. Hope this helps some. :drink
 
Coils and spark plug wires are most likely the reason it won't start. Spray the WD at the coil tops, they REALLY don't like getting wet!
 
Thanks

Thanks guys for the replies.

The backfire seems to be coming from the exhaust pipe (right I believe).

I will hit everything with WD-40, drop the carb bowls, check the oil, etc and report back tonight.

I did check the plugs last night (dry tips...tops were a little wet from the previous washing) and the air filter (relatively dry....just a few drops around the top seal).

I have had a recent issue where the right carb leaked excessively once when I forget to turn the fuel valve off. But this is definitely the first time it has failed to start and since it happened right after washing I suspect something electrical/water instrusion.

By the way, this is a '91 Monolever airhead....no points....electronic ignition:
http://www.bmbikes.co.uk/specpages/r100mono.htm for bike specs.

Thanks! Brian
 
Had you just ridden the bike prior to washing it? Was it hot?

Also, try to recall how much water you got into suspect areas, like kill switch, ignition switch/headlight area.

I vote for water in the bowls, since it cranks, has spark but no firing. That and backfiring, sounds like a fuel delivery problem. I dunno, just theorizing. Its half the fun.
 
More info

The bike was not hot when I washed it. It just would not kick over afterwards.

I checked the carb bowls just a little while ago....full of gas with no signs of water (I drained them and verified no water by doing an ethanol jar test). No water in the oil either. I sprayed everything with WD-40 as recommended and took the battery off the float charger (even though I am confident the battery is not the issueit is nearly new). I will give it a few more hours to ensure drying, put everything back together and give her a try again.

Seems like it (hopefully) it is just the spark plug wires/tops being too wet. I got spark when I removed and touched each spark plug to the cylinder while cranking.but maybe not hot enough spark necessary to turn it over???? I sprayed them with the miracle WD-40 too. Will report back later.

Thanks, BK
 
Last edited:
Good news-Bad news

Good news- I put my R100 back together and got it started. It ran a-ok and I rode it briefly around the neighborhood.

Bad news- The neutral light does not work, I have to hold the clutch in to start the bike so I fear some water got into the instrument cluster and possibly shorted it out or at least burned the bulb out. Does that make sense?

So....my next mini-project is to take apart the instrument cluster and use more of the magic WD-40.

Thanks again for all your suggestions...it really helped...that is what makes this forum and MOA great.

Cheers, BK
 
Good news- I put my R100 back together and got it started. It ran a-ok and I rode it briefly around the neighborhood.

Bad news- The neutral light does not work, I have to hold the clutch in to start the bike so I fear some water got into the instrument cluster and possibly shorted it out or at least burned the bulb out. Does that make sense?

So....my next mini-project is to take apart the instrument cluster and use more of the magic WD-40.

Thanks again for all your suggestions...it really helped...that is what makes this forum and MOA great.

Cheers, BK

Let me know on the neutral light. My starter relay went bad and I ordered a replacement on-line but I ordered the wrong one. When I put it in, the neutral light came on without the switch on and when I turned the switch on, wires smoked. When I finally put the right one in (Thank you Jason at Hammersley), everything worked OK except for the same problem you have. I removed gauges and verified the bulb was OK but the problem persists. I suspect it is the neutral switch in the transmission.
 
Good news- I put my R100 back together and got it started. It ran a-ok and I rode it briefly around the neighborhood.

Bad news- The neutral light does not work, I have to hold the clutch in to start the bike so I fear some water got into the instrument cluster and possibly shorted it out or at least burned the bulb out. Does that make sense?

So....my next mini-project is to take apart the instrument cluster and use more of the magic WD-40.

Thanks again for all your suggestions...it really helped...that is what makes this forum and MOA great.

Cheers, BK

Hey, great news and nice looking bike.
 
Good news- I put my R100 back together and got it started. It ran a-ok and I rode it briefly around the neighborhood.

Bad news- The neutral light does not work, I have to hold the clutch in to start the bike so I fear some water got into the instrument cluster and possibly shorted it out or at least burned the bulb out. Does that make sense?

So....my next mini-project is to take apart the instrument cluster and use more of the magic WD-40.

Thanks again for all your suggestions...it really helped...that is what makes this forum and MOA great.

Cheers, BK

Try removing wire and grounding it. If light glows it's the switch. I suspect it's a lot easier to ground the wire than to get involved with the inst cluster. Make sure to turn key on when grounding the wire.
 
Which wire?

Which wire are you suggesting? Thanks, BK

Try removing wire and grounding it. If light glows it's the switch. I suspect it's a lot easier to ground the wire than to get involved with the inst cluster. Make sure to turn key on when grounding the wire.
 
I then pulled each plug and while cranking touched the cylinder to verify I was getting spark....check. Towards the end of my spark check I got a loud BANG that surprised me....a backfire.

Be careful about pulling a plug and grounding it. From what I've read, pulling a plug and grounding it is not a good idea for bikes with the electronic ignition. While it is recommended to pull a plug and do that for bikes with points, doing it on bikes with the electronic ignition can damage some parts.
 
Be careful about pulling a plug and grounding it. From what I've read, pulling a plug and grounding it is not a good idea for bikes with the electronic ignition. While it is recommended to pull a plug and do that for bikes with points, doing it on bikes with the electronic ignition can damage some parts.

Electronic ignitions require that the spark plug wires be grounded to avoid damage.

Ralph Sims
 
Thanks for the advice....luckily I didn't blow myself up :>)

By the way...I noticed that the OIL light does not come on either (not sure if it did before or not) but it should when the key is turned ON.

So to summarize...the only issues with the bike I have now are that the NEUTRAL and OIL lights don't work and I have to pull the clutch before starting (because the neutral light/switch doesn't work). BK
 
Sorry, To test the oil, neutral lights, ground those wires. A spark plug should be grounded-it won't spark if it's not grounded. Damage can occur to any electronic ign sys, if plugs are not grounded. Safest way to check compression, points or electronic is to disable ignition system, by disconnecting coils or jumper wires; from spark plug wire to ground
 
Next?

I went ahead and removed the instrument cluster since I've never done it before on an airhead and since I needed to replace the tach light bulb too (it's been out since I bought the bike). I checked all the other lights (OIL, NEUTRAL, GEN) and the bulbs are all good.

So what is next? Replace/repair the switch/ignition?

Thanks, BK
www.brainsflight.com
 
You have an electrical problem, that I doubt very much has anything to do with your gauges in the instrument cluster. It sounds like you have a bad ground somewhere. My guess it is the lower wiring harness that goes to your neutral light swith on the bottom of the tranny and the oil pressure switch (below the left head). Trace those wires from the bottom up.
BTW, I got the same problem right now. I took 1/2 day off from work to fix it and fixed it in the garage and on the driveway, but as soon as I was on the street it returned. Thank goodness it does not affect the ride, just an annoying light and I still have to find the bad ground. The wiring part is available for less than $50; but is a pain in the a** to replace, due to the neutral light switch. And I just replaced it in December of 07, so much for German quality control; but that was over 10,000 miles ago too... bummer. Good luck finding the loose ground.... Let me know wha tyou find....
 
Will check for bad ground

Thanks Boxerkuh for the advice.

Ironically I picked up my elderly mother from the airport late last night for a visit before my oldest daughter leaves for college in a couple days. Amongst other things, we started talking about motorcycles. She asked how my bike was running. I explained the situation to her and she simply said, "sounds like you have a bad ground." Too funny....never underestimate the knowledge of an old farm girl....now if I can just get her to go out to the garage and fix it for me while I am at work :>)

Cheers, BK
 
The oil and neutral switches are on the same wire harness. It runs down the left side of the rear main frame and under the shifter. There is a connector up by the battery..see if that's disconnected. Better yet, unplug it, clean it and connect it back.

There are 4 connectors on the lower harness. One goes to the oil pressure switch that sticks into the engine block under the left cylinder, another is the ground that connects to the bottom left side transmission mounting bolt, and the final 2 go to the neutral switch up under the tranny.

Check the connector,,then the ground wire,,then pull the oil pressure switch wire off and ground that with the key on. The oil pressure light better come on then.
 
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