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Thread: Bosch spark plug question

  1. #1
    DennyPink
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    Bosch spark plug question

    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

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    unopened, you should be able to return them; especially if you seek an exchange for the correct item.
    Ride Safe, Ride Lots

  3. #3
    Registered User jad01's Avatar
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    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.
    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
    '90 and '93 Mazda Miatas (Jelly Bean and Red Hot), '02 325ci (Blue Streak)
    '96 Giant Upland (big Kendas & freshly greased bearings!)

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    Administrator 20774's Avatar
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    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.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
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    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    Registered User jad01's Avatar
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    Quote Originally Posted by 20774 View Post
    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/mechani...n/spark-plugs/

    This has a complete compatibility chart:
    http://www.clubplug.net/bosch_ngk.html
    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
    '90 and '93 Mazda Miatas (Jelly Bean and Red Hot), '02 325ci (Blue Streak)
    '96 Giant Upland (big Kendas & freshly greased bearings!)

  6. #6
    Registered User lkchris's Avatar
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    Quote Originally Posted by jad01 View Post
    I'm not sure you will be able to find Bosch W7DC plugs easily...
    It's as easy as a trip to your BMW dealer.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  7. #7
    Registered User jad01's Avatar
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    Quote Originally Posted by lkchris View Post
    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.

    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
    '90 and '93 Mazda Miatas (Jelly Bean and Red Hot), '02 325ci (Blue Streak)
    '96 Giant Upland (big Kendas & freshly greased bearings!)

  8. #8
    Registered User lkchris's Avatar
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    "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.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  9. #9
    Bluenoser
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    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.
    1971 R50/5 SWB with R75/6 drivetrain
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  10. #10
    Registered User lkchris's Avatar
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    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.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  11. #11
    Registered User helmut_head's Avatar
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    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......................

    HH
    Helmut always wears a Helmet.

  12. #12
    Registered User helmut_head's Avatar
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    Quote Originally Posted by lkchris View Post
    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.
    Helmut always wears a Helmet.

  13. #13
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    Quote Originally Posted by jad01 View Post
    I do see on the parts fiche that MAX BMW carries them (W7DC) for $6.88 each.
    Thats what my dealer sent.

  14. #14
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    Quote Originally Posted by DennyPink View Post
    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.

  15. #15
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    Look on eBay. I got a bunch of NOS W6D's there a while back for about $1.50 each.
    1983 R100RS (Sold)
    2004 R1150RT
    BMW MOA 181289
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