Ngk g r 4
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Road Warrior
Joined: Sep 2005
Posts: 1,569
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From: Arizona
Ngk g r 4
friend of mine has these plugs in his 89 fxr and swears by them. NGK GR4 #2635. he tells me he was fouling plugs in a couple weeks and his idle wasnt consistent. i looked up these plugs and tells about the V groove but doesnt say they fit a harley. it showed a different NGK plug for my bike but i didnt like the fact that it has a screw on cap, ive had these vibrate loose before.any one tried these GR4 plugs.
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
We use and reccomend Autolite coppers for 99% of the engines we build. Plugs are fairly inexpensive, so we change them with every oil change. You won'r see any measurable HP difference between plugs, unless you have the wrong/bad plug installed.
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Road Warrior
Joined: Sep 2005
Posts: 1,569
Likes: 12
From: Arizona
i found them. looks like they have the screw on cap. ever have any problems with the cap coming loose from vibration. also when i cross reference it comes up with a Autolite 4265. is the difference that one is copper and the other isnt. it list the copper for the twin cam 88 inch. is it a different heat range. my motor is stock except for a cam, ev27.
Last edited by hotrod351; Oct 25, 2009 at 09:01 AM.
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
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From: Bluffton, South Carolina
Hotrod,
The 5 is a little hotter. Different manufacturers use different number/letter combos for their plugs. Additionally different manufacturers have more or less sparkplugs in heat ranges for a particulars size.
Here is Autolites site which has a wealth of info. We have it bookmarked on our computer so tha a customer can look at it instead of us trying to explain it too them. Hope this helps.
http://www.autolite.com/carcare/techSpecs.php
The 5 is a little hotter. Different manufacturers use different number/letter combos for their plugs. Additionally different manufacturers have more or less sparkplugs in heat ranges for a particulars size.
Here is Autolites site which has a wealth of info. We have it bookmarked on our computer so tha a customer can look at it instead of us trying to explain it too them. Hope this helps.
http://www.autolite.com/carcare/techSpecs.php
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Road Warrior
Joined: Sep 2005
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From: Arizona
thought about it abd ill stay with the champions, after all thats what the bike came with and ive never had any problems with them. my friend is running the ngk gr4,s because he was fouling plugs, well im not so i figure why switch to a plug that may or may not be the right heat range.
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HDF Community Team
Joined: Dec 2005
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From: NC USA
thought about it abd ill stay with the champions, after all thats what the bike came with and ive never had any problems with them. my friend is running the ngk gr4,s because he was fouling plugs, well im not so i figure why switch to a plug that may or may not be the right heat range.
Anyway, point being - if you need a hotter than factory spec plug, then you should look for the problem because it's likely NOT the heat of the plug causing the fouling.
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