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2000 R1100RT: Coil or HES?

Jeff488

Aspiring Profligate
142k miles.
This is a friend's bike.
Died on the road. After cooling a bit, it restarts and runs for about 45 seconds.
Pulled the coil and noticed a very slight bulge and a separation where the epoxy joins with the edge of the black plastic body of the coil.
Secondary coil read 7390 ohms; primary reads 1.75 ohms. Used two different VOMs.
AFIK, it should be 15k and .5 ohms, respectively.

Am I on the right track thinking the culprit is the coil?
Also, should we rewire the HES as long as we are in there?

TIA,
Jeff
 
While both are possibilities, I would check the volume of fuel flowing in the return line to the tank to make sure you don't have a leaking hose in the tank.

If all is well with the pump filter and hoses you'll have about 2 liters per minute flowing back to the tank at idle.
RB
 
The internal tank line is certainly a very strong possibility (they do have a history), and when were the two fuel filters changed; but any physical distortion of the ignition coil makes it highly suspect regardless of the resistance. Can you compare it to a new one at the dealer's? They're difficult to test under actual "operating conditions" unless the failure becomes total.

And yes, an older 1100 deserves upgraded wiring, even if it's not the present "Root Cause" - it soon will be...
 
All of the above

A bike that old is due to have all those components replaced. It is much easier to do it in the garage than on the road.
 
OK, I got a better look at the wires to the HES at the connector.
Complete toast. THe insulation is crumbling off all the wires. So that's one mystery solved.
We have decided to replace the coil as well.
Plus, while we have the tank off, we'll do the internal hoses.

I'm still curious about the coil resistances and why they are so out of tolerance.
Perhaps this has caused a mis-firing at times.
My buddy did say that his mileage has dropped to about 34 mpg recently, and I'm guessing that's related.

Anyway, my buddy is looking on line for an HES that's been rebuilt and a coil from Beemer Boneyard perhaps.
Suggestions are appreciated.
Thanks,
Jeff
 
Last edited:
142k miles.
This is a friend's bike.
Died on the road. After cooling a bit, it restarts and runs for about 45 seconds.
Pulled the coil and noticed a very slight bulge and a separation where the epoxy joins with the edge of the black plastic body of the coil.
Secondary coil read 7390 ohms; primary reads 1.75 ohms. Used two different VOMs.
AFIK, it should be 15k and .5 ohms, respectively.

Am I on the right track thinking the culprit is the coil?
Also, should we rewire the HES as long as we are in there?

TIA,
Jeff

FYI the BMW Shop Manual has a coil specification mistake that has been copied in every manual I've seen. It states 0.5 Ohms for the primary. It's usually higher than that...
For the secondary the BMW manual states 13K Ohms for the secondary but should be 7.5K Ohms.

So what you measured on the secondary is bang on. This does not mean it will perform properly under load though and many have been fooled by that. If it's cracked or bulging I would definitely replace it. Probably put new wires in at the same time since they are probably just as old. Euromotoelectrics sells coils and a good wire set for a decent price.
 
Update

My bud has ordered the HES plate assy, coil, and plug wires from euromotoelectric.
Should be here by Thursday.
We might have it operational by the weekend.

As Johnny would say "More to come".
 
All parts installed and the bike was ridden today for about an hour with no issues.
Always nice when a plan comes together.

Thanks for the input.
Jeff
 
Thanks, that's very kind, but my buddy did the dirty work. He's learning fast.

I and another friend supplied the guiding harassment, not to mention his big, beautiful shop as
I didn't have room for another bike.
 
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