Sparkplugs..Use 'em if you got 'em?

[ryan_a1982]

Hello,

 

I have 4 spark plugs from the beemerboneyard from my last 12k/24k kit I ordered. I am getting ready to do the 12K service and I ordered everything I need sans plugs. (2007 R1200RT)

 

Question: Should I install the plugs I have now, or should I just keep them until I hit 24k miles? Would there be any benefit to replacing the factory ones at 12k?

 

Thanks!

 

-Ryan

[dirtrider]

Afternoon Ryan

 

Your call, even 24K is pretty conservative as far as I have seen for plug wear on the heaxhead.

 

Why not measure the electrode gap & see where you stand on electrode gap wear (you need a round gauge set for those side electrode plugs). If close to the wear limit then replace, if still a long ways from upper limit then wait till 24K.

 

I would be real surprised if you measure much of any wear at 12k on the plugs in that hexhead.

 

[ryan_a1982]

Thanks D.R. I'll check them.

 

-Ryan

[SoulBait]

I thought you replaced plugs every 12k is that just for the first 12k service?

[BMWRich58]

Just for sh#ts n giggles..I left them alone till 39K...some noticable wear but then again very little when compared to new.

MPG's were always still the same with the original plugs...nuthin' changed...

I'd say 30-35K and then change, but do keep an eye on at the 6K intervals.

 

[racer7]

On my 08 RT I measured and photographed the wear on the stock NGK plugs (a "BMW bike only" item but why that is so is a bit of a mystery). Bottom line is that at 24K they were worn to 1.1-1.2 mm, a bit over the wear spec though the bike ran fine at that gap. When new such plugs are 0.8 mm gap.

 

For replacements I used a physically identical NGK plug that has platinum electrode rather than nickel-copper of the stockers. In theory it might wear a little more slowly but I note that, unlike most platinum plugs, its center electrode is the same diameter as the nickel copper version. In 24K mles, I'll know whether its better or not.

If you want to try it, you can get it commonly on the web or at any place selling NGK plugs- its the stock plug for some BMW 6 cyl car motors (so why nickel copper variant in the bike??). Its cheaper than the stock plug, also. The RT erodes its stock plugs faster than any of my cars eat theirs despite the low RPM of the boxer motor.

 

If its not better, my next try might be single electrode iridiums, indexed properly (look up how to index a plug if you're curious about this- you need spacers for this old racers trick) but iridiums a still pricey..

[Selden]

Not a hexhead, but I replaced the plugs (Autolite AP3923on my R1100RT at 22,000 miles, then went on an 1800-mile trip. Gas mileage was about 5% better than my previous ride on roughly the same route in April. Lots of variables, so I'm not claiming that changing the plugs was the cause, but it didn't hurt.

 

A little off topic, this month's MCN has an article on indexing washers. I understand the theory, but I am skeptical of the claims. I e-mailed MCN, and had a few exchanges with Dave Searle, including this quote from NGK:

 

However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.

 

In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.

Basically the exchange between Searle and me was "indexing works" vs "show me the data."

[dirtrider]

Evening Selden

 

 

I haven’t tried indexing the plugs on any of my 1200’s as I use the dual electrode plugs. The secondary plug is pretty shrouded anyway so not much gain to be had down there. In fact maybe a loss if using a single electrode plug with a partial covering ground electrode.

 

On my Harley I can definitely see the difference in plug indexing on the Dyno but sure can’t feel all that extra 1.5 hp while riding it. Strange thing is I have a tunable coil module on that bike & the indexing seems to work better when I set the module to spark on every piston up rather than only on compression (maybe the cam overlap or a reversion thing as that bike has a lot of cam in it). I try not to use washers to index if at all possible as I don’t like changing the heat range of the plug so just buy some extra plugs and can usually find a plug that indexes correctly & still stay within the torque range.

 

I tried indexing the 3923’s on my 1100’s and the 3922’s on one of my 1150’s & definitely couldn’t feel any difference in power or acceleration. Never showed any on the Dyno Jet either. It didn’t seem to effect the surging for the good or bad as far as I could tell seat of pants. Didn’t gain me any top speed either (a good test if any power gain).

 

Indexing spark plugs is kind of a PITA so unless there is real noticeable gain or reason to do it it’s not worth the hassle to me.

 

[racer7]

True enough- indexing isn't going to gain big power but can gain a little or smooth out shrouding effects/lean programming in some stuff. The reason I'm trying the platinums is they're the only alternative I know of in the dual electrode config and I wasn't overly impressed by the durability of the stock NGK items. (I've got car plugs with 100K miles with less wear and they're in a turbocharged motor running 15-18 lbs of boost!). Racers, of course, use the dyno as needed and will do all sorts of stuff for an extra hp but my RT is no track toy so that's not motivating in this case.

 

Indexing spacers are pretty thin and the needed thickness can be calculated from a trial fit of a marked plug using thread pitch info so its not like its huge work to do - you don't have to do it 5 times or do continual trial and error to get the thickness that works . I'm not aware that a proper choice does anything substantial to heat range but am open to any info on that.

 

I'm not surprised that some engines work best with the gap in an opposite position given all the types of combustion chamber designs. It would be interesting to see a lot of that data and see what correlations exist between the engine design (combustion chamber, cam and spark timing, etc.) and indexing preference

[Dave_in_TX]

On my 08 RT I measured and photographed the wear on the stock NGK plugs (a "BMW bike only" item but why that is so is a bit of a mystery). Bottom line is that at 24K they were worn to 1.1-1.2 mm, a bit over the wear spec though the bike ran fine at that gap. When new such plugs are 0.8 mm gap.

 

For replacements I used a physically identical NGK plug that has platinum electrode rather than nickel-copper of the stockers. In theory it might wear a little more slowly but I note that, unlike most platinum plugs, its center electrode is the same diameter as the nickel copper version. In 24K mles, I'll know whether its better or not.

If you want to try it, you can get it commonly on the web or at any place selling NGK plugs- its the stock plug for some BMW 6 cyl car motors (so why nickel copper variant in the bike??). Its cheaper than the stock plug, also. The RT erodes its stock plugs faster than any of my cars eat theirs despite the low RPM of the boxer motor.

 

If its not better, my next try might be single electrode iridiums, indexed properly (look up how to index a plug if you're curious about this- you need spacers for this old racers trick) but iridiums a still pricey..

 

Iridiums pricey? Single electrode NGK iridium plugs are cheaper than the platinum NGK dual electrode plug that fits the RT.