spark plugs

[Clutch]

ugghh,  I know this has been talked about before and I could probably go to the old sites and find it, but I figured I'd save someone having to cut and paste it into this forum.

My bike currently has Bosch W5DC plugs in it, but Bob's BMW lists the W6DC's for the 1981 R65.  Everyone please chime in and let me know what you think I should be running in my bike.  I'm fixing to buy some new ones, so if you've found a cheaper source than Bob's, then you can let me know about that too.  I've only checked one local auto parts store so far, and they didn't have the plugs.

thanks

[Bob_Roller]

If you have a NAPA store around, they usually have the common Bosch plugs in stock. I replaced my plugs about 6 months ago, and they were 95 cents each. I'm using W6DC, on suggestion  from Oak of Airheads Tech fame. Is your bike azure blue, paint code 158 by chance?

[Clutch]

I'm not sure about the official name of the color.  Whatever turquoise color they used in 1981 is what I have.  It hasn't been repainted.  Thanks for the reply.  I may just go to the W6DC.  Do you think I'll have to do any carb adjustments if I change plug models?

[Justin B.]

I thought the W7DC are for the R100s?  I run the W7DC in the R100 and W5DC in the R65.  As far as prices, just about enybody will be cheaper than Bobs.  You should be able to get the standard Bosch plug at any auto parts store.  If they don't stock them they can get them in a day or two.

[Semper Gumby]

The BMW Rider's Handbook states that W5DC is the plug for the 1981.  But I have "heard" of people using a hotter plug for better starting in the cold wx.  I have used both and cannot tell the difference.  I hope this means my set up is *perfect* .  (One can always dream....)  I am currently using the W5DC gapped wider than normal as I have a higher voltage coil than stock.

[Baffo]

I run NGK BPR6EIX iridium plugs and found these standard plugs and alternatives for mine:

Sparkplugs      Bosch W7DC, Beru 14-7DU, Champion N9YC, NGK BP(R)6ES             
Alternative Sparkplugs      NGK Iridium BPR6EIX, BP6EY, Denso Iridium IW20, Splitfire SF6D

[Semper Gumby]

Ah Baffo,

Resistor plugs - I have the NGK 5000 ohm caps so I won't use a resistor plug.  I have "heard" that the combination of the two will cause your coils to really heat up.

Hi Clutch,  I think you can set your carbs a bit richer if you want to but if you don't have any noticible problems (popping on deacceleration, hard starting, etc.) just leave 'em where there at.

Bill

[Baffo]

Yeah I know unfortunatelly NGK sells caps with resistors only at least here in NL, and the iridium only come with R in it, never had problems with the combo (but wouldn't do it with normal plugs) still have the Iridium benefits of better starting and better fuel, and better idle, so I take my chances, and I got rid of the green/gray coils for the black one with red sockets

[Clutch]

I guess I'll just stay with the stock W5DC.  I do get a little nervous when deviating from the original equipment - not knowing the subsequent consequences and extra work I'll have to do to compensate.  I have been riding almost every day, except when rain is expected, but I'm really having to crank on the starter to get it running in the morning since it has gotten cold.  I switched out the plug wires, and I'm gonna get some new plugs too.  I haven't checked the strength of the signal in the wires yet to see if I need a new coil.  I guess I autta re-check the carbs too.  After thanksgiving I'll have a little more extra time to do this stuff.

[Bob_Roller]

What kind of problem do you have when starting? The scenario that I had, was at 55 F. the bike started having difficulty starting on the first cold start of the day. This would get worse, until at 48 F. the bike refused to start. You could smell fuel coming out of the exhaust,and pulling the plugs and checking for spark, showed nothing out of the ordinary. I found the primary coil resistance was on the low side (.6 ohms) replaced the OEM coil with a Dyna brown coil, and the hard starting went away.

[Clutch]

Well, I've started my bike on mornings when the temperature has been slightly below freezing, but it has taken probably over a minute's worth of crank time and I'm sure I've p'd off the neighbors in the process.  It is very hard to tell any change from when it will run on it's own and when I have to keep cranking.  You know usually a bike will jump in RPM's when it is running on it's own.  Lately mine will barely chug for about 10-15 seconds once it has started, and then will jump up in RPM's correctly.  All the while I have to find just the right amount of throttle to apply (very small amount) in addition to being fully choked to get it running.   I have noticed an occasional gas odor, but I figured it was because of my flooding the carbs with my small amount of throttle.

[airhead]

Ah Baffo,

Resistor plugs - I have the NGK 5000 ohm caps so I won't use a resistor plug.  I have "heard" that the combination of the two will cause your coils to really heat up.


Bill

The extra resistance will actually limit the secondary current flow and if anything the coils will run cooler!! The amount of resistance with the voltages concerned (20-40kV) is minimal and of little consequence. I am running resistor plugs and caps and have absolutely no problems with cold starts or running, and have a nice fat blue spark.

Bill.....................;-)

[Justin B.]

Clutch, for normal everyday riding it is probably good to keep the stock plug.  The normal rule of thumb is - mostly highway riding - go down one heat range, mostly city - go up one heat range.  The plug's heat range has nothing to do with how "hot" the charge burns but ho they dissipate heat.  A "colder" plug will sink heat out to the head at a faster rate than a "hot" plug.  Or, did I get that backwards?  My brain's fried...

[Bob_Roller]

When you get time, I would remove the fuel tank and get a good look at the ignition coil, if it is the original gray, I would replace it now and get it over with. If it happens to be the upgraded version, the outputs that the ignition leads slide over, are red in color, check the resistance of the primary circuit (1.5 ohms) and secondary circuits (around 12 k ohms). My OEM upgraded coil had .6 ohms on the primary. Appearantly the insulation brokedown inside the coil, I'm sure the desert heat of Phoenix had nothing to do with it's demise!

[Semper Gumby]

Perhaps a bit of reading is in order.  What kind of resistor plugs and caps are you using?  I have been tempted to try the NGK iridums.  But my bike works in all temperatures...I hate tweeking what aint broke!

Bill