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Bosch spark plug question

dennypink

DennyPink
Fellow Airheads;

I made a purchase ass-backwards. I bought a 4 pack box of Bosch WR7DC spark plugs, then read Snow Bums article and he recommended against using any plug with the "R" letter, meaning it is a resistor or resistance plug, not to be used in airheads. My 1992 RT owners manual recommends Bosch W7DC. Do I now own 4 paperweights? Thoughts please. Thank you!
Denny Pink
 
I'm not sure you will be able to find Bosch W7DC plugs easily... you may want to opt for NGK plugs which are equivalent and readily available.
 
Be sure and find the right matching when going to NGK. The temperature rating scheme on the plugs are different. IIRC, Bosch W5 is a colder plug than a W6...reversed on the NGK.
 
Be sure and find the right matching when going to NGK. The temperature rating scheme on the plugs are different. IIRC, Bosch W5 is a colder plug than a W6...reversed on the NGK.
Yes- good point! The numbers do go in opposite directions for the two brands. I think the Bosch W7DC equivalent NGK part number is BP6ES. That said, I see Rick (Motorrad Elektrik) is recommending NGK BP7ES for all 1000cc twins '81 and onward:http://www.motoelekt.com/ignition.htm (scroll to the bottom).

I recall Snowbum has a comparison table: http://bmwmotorcycletech.info/sparkplugs.htm

Here are couple of other pages from the net that might be helpful...
This page has a nice chart about halfway down the page showing the compatible the NGK and Bosch plugs from hotter to colder:
http://matchlessclueless.com/mechanical/ignition/spark-plugs/

This has a complete compatibility chart:
http://www.clubplug.net/bosch_ngk.html
 
It's as easy as a trip to your BMW dealer.
Mmm... that maybe true for some dealers. My local dealer only carries the NGKs these days. So... your results may vary!
I do see on the parts fiche that MAX BMW carries them (W7DC) for $6.88 each.

:beer
 
"Carries" is a vague word here.

Your BMW dealer has a BMW part number for the Bosch plug.

He doesn't for any NGKs for Airheads.
 
Run the plugs that you've bought. I would be surprised if you had any issues contrary to popular opinion. The 5k resistance isn't going to hurt anything. I can't think of any electronic ignition that is going to be bothered by that small of a resistance level. You'll have more issues with bad wires or bad plug caps than you will have with that small of a resistance. In fact if you are going to go to NGK go to Iridiums. I've used them on point ignition equipped bikes and they work better than the stock plugs.

If not then take them back and try again.
 
American BMW owners often seem to STRONGLY resist the following truism:

If you own a German vehicle, they DO NOT have parts for your bike at PepBoys, NAPA, etc. Pretty unlikely at "motorcycle superstore," too.

Now that you own a European vehicle it's time to leave old American ways behind and catch up to your bike. Yes, it's a culture shift.

When your bike was designed, there was ZERO consideration given to whether it could be maintained by typical American DIY methods. You'll have trouble forcing this approach on your bike. Go to Germany some time and see if you can find a PepBoys.

Various importers, including your dealer, are your best bet. Heck, I've ordered tires for my G/S from the UK.
 
NGK Iridiums work nice. Funny thing happened to me. I ordered 2 from Amazon, they sent me two boxes full (16 pieces) for about $12.00.

I returned the spares......................:brow

HH
 
American BMW owners often seem to STRONGLY resist the following truism:

If you own a German vehicle, they DO NOT have parts for your bike at PepBoys, NAPA, etc. Pretty unlikely at "motorcycle superstore," too.

Now that you own a European vehicle it's time to leave old American ways behind and catch up to your bike. Yes, it's a culture shift.

When your bike was designed, there was ZERO consideration given to whether it could be maintained by typical American DIY methods. You'll have trouble forcing this approach on your bike. Go to Germany some time and see if you can find a PepBoys.

Various importers, including your dealer, are your best bet. Heck, I've ordered tires for my G/S from the UK.

Sad truth, you can buy oil, but even most metric BMW bolts are difficult for the American auto parts store.
 
Fellow Airheads;

I made a purchase ass-backwards. I bought a 4 pack box of Bosch WR7DC spark plugs, then read Snow Bums article and he recommended against using any plug with the "R" letter, meaning it is a resistor or resistance plug, not to be used in airheads. My 1992 RT owners manual recommends Bosch W7DC. Do I now own 4 paperweights? Thoughts please. Thank you!
Denny Pink

Try parts stores that sell VW Bug parts. JBugs lists the W7DC as being available. $3.00 each.
 
For several of my past bikes, and my present 1150, NGK plugs have always surpassed Bosch for performance and longevity. My local O'Reilly Auto Parts can get them in two days (and they appreciate that I'll pay in advance just to prove that I really want them and I'll be back to pick them up).
I've posted these charts before, but the recent forum upgrade may have nuked 'em, so here ya go.
 

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still confused about which ngk?

If you go to the ngk website, and look for bmw, 900cc it will recommend BP6ES plugs. Seems a perfect match according to the charts in the previous reply.
I have used them since 1975 when Bosch plugs were not available with no problems.
 
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