A little help with spark plugs?

[pat76r90]

So, it's been two great weeks aboard the R/90, I'm really enjoying this bike. Smooth, reliable, stable in the rain as long as I am careful with the downshifts. Great looker too, I leave it parked right outside my work bay, where it is within eyeshot all day. I took it to a concert Friday night, and got more compliments on the bike than complaints about my lanesplitting.

Which brings me to this morning, I am going to install a new set of points, and lube the advance mechanism, as I am getting an intermittent high idle. I pulled the plugs out to make turning the engine over easier, and lo and behold, two different styles of plugs both Bosch,W8LCR (371 on porcelain), and WR7CCX(062 on porcelain). The latter plug has the ceramic core completely shrouded by the plug body, the first has the ceramic exposed a few mms.

I looked up at the Bosch site, 7995 is what they call for, anyone have any input? From what I can see the W8LCR is probably closer to correct. I am going to town to see what I can come up with, I'd like to stick to Bosch plugs if possible, but would accept a NGK or Denso substitute.

Both heads have the same number of cooling fins, any reason anyone can think of why someone would put a different(shrouded) plug in? Are heads different different years, or is this just another example of a previous owners inept attempts at......

To my inexperienced BMW ear, the bike runs strong, burns no oil I can tell, is a bit cold blooded, but runs more than acceptably.The right cylinder, with the longer reach plug has look of oil from a valve guide or seal, concentrated on one half of the plug, the shrouded plug looks pretty happy.

[chasbmw]

I would fit the equivalent NGK plugs, your bike should not have resistor plugs and all Bosch plugs apart from some for sale at BMW dealers have resistors (that's what the R means in your plug numbers) I Think that NGK plug ref is BP7 ES.

You only have one plug for each cylinder Right?

If someone has fitted 2 plugs to each cylinder, then the lower plug has shorter threads and the designation should be BP7 HS. Don't fit the longer plug into the lower cylinder!

[Duane Ausherman]

You need to do more reading before jumping in. It is highly unlikely that your idle issue is related to plugs. That is a common problem and there is an easy test to see if it is carbs or ignition. Go to w6rec.com to read about it.

[pat76r90]

, I am going to install a new set of points, and lube the advance mechanism, as I am getting an intermittent high idle. I pulled the plugs out to make turning the engine over easier, and lo and behold, two different styles of plugs

I wasn't planning on changing the plugs until I saw the two different plugs. I was having no running issues other than the intermittent high idle. I had bought a new set of points, and hadn't had a chance to even check the old ones.

The engine is not dual plugged. Looks like probably someone threw in something that would fit, maybe a shorter reach plug from a dual plug system. I'm surprised the bike ran as well as it did.

So the new points looked pretty well identical to the old, condenser was not Chinese, and I went ahead and installed them, along with a pair of NGK BP6ES spark plugs. Wouldn't you know, ran like crap afterword, breaking up on accel, not running over 2k. With panicked visions of frankenstein/2 different head motors, I went back over everything i had done, triple checked points gap .015" , both lobes, every time. Finally, while running it with the cover off, I saw the wire at the points block arcing to the advance mechanism. The spade terminal on the old one had been bent over to increase the clearance, and that is what this one needed as well. Whew. I set the timing statically, and checked it with a light, S is pretty much in the middle of window, and I can just start to see the F as I rev it up. Tried my hand at ear setting the carbs, shorting one cyl out at a time, and I have it running at least as well as it was before I started screwing with it, maybe better.
Next free weekend, valve adjustment.