Mileage For Spark Plug Change

[JimLor]

I'm at the 4k mark where the maintenance sked calls for pulling and cleaning the plugs (changing them at 8k). What experience have others had - do I really need to pull them at 4k/chg at 8//should I wait and change to Iridium plugs - has anyone seen any difference with Iridium plugs? I'm going to pull them anyway for the experience/practice and do a TBS while I'm in there. Appreciate your comments.

 

[Warchild]

Pull the OEM plugs at 8K. They are toast by then, believe me.

You'll read how some here claim they've run 24,000 miles on the oem plugs "without any problems". Yeah, okay, sure they have.... whatever. The EFI system does a lot of compensation for worn plugs, so many riders don't notice the falloff in performance (it's subtle, but definitely there). Trust me, the OEM plugs are the bottom-of-the-barrel variety.... another cost-saving measure by Yamaha. They are not even platinum, or anything special at all.... ithey are the kind you'd put in your lawn mower.

Swap them out with the Irridiums, and start living the good life of 16K intervals:

Source: NGK CR8EIX Irridium spark plugs

 

[maddawg46]

I just did mine at 10K. They looked perfect coacoa brown. All were the same which is great news. No sign of lean mixture. I have a stock system. I did however replace with the NGK recomended and did not put in iridium plugs. I probably wont look at them now for another 15K. It is good to check the first time to see how your engine is performing to give you a warm fuzzy, then you can make up your mind how long you want to go.

 

[mech 1 twa]

I have 10k on mine, runs great. I'll run them rest of this season, change in spring.

Other bikes i've owned plugs lasted this long, i don't see any problems running them a little more miles.

 

[radman]

Said it before, but bears repeating-motors love fresh plugs. I use the Iridiums on Frank, the best NGK's on all my bikes, and I change every season or 3-4000 miles at the most. Some consider it a waste, their stuff rarely runs as well as mine. Plugs are no longer as readable as they once were-modern ignition and accurate fuel mixing has more or less made reading as anachronistic as generator polarizing. As a result, other than gap erosion, it's hard to tell when a plug is on the outs, till the odd misfire starts taking place. Performance has seriously deteriorated at this point, and the plug has been costing you performance and mileage for quite a bit. Another reason to change them more often is so that you can ; a plug left in an aluminum head too long can and will take the threads out with it upon removal, an expensive proposition. The carbon buildup on the exposed tip is as good a metal stripper as they come-diamonds after all are simply compressed and heated carbon. The naysayers will throw their two bits in now, but they won't be there to help pull the head, or help diagnose that funny high speed stumble. Plugs, like oil, are cheaper than the alternatives, and your motor will love ya......

 

[yamaholic]

I agree with Warchild and Radman.

Old plugs slowly decrease performance. Makes your ignition system work a lot harder, too. Just like a dirty airfilter, you won't notice the loss over time. Put new ones in before 8K.

I'm using the splitfire SF430C (CR8E equivalent), solely because of excellent experience (ie no fouled plugs, better starting, more power felt, crisper running) with them on finicky, high compression 4 stroke dirt bike engines pushing way more HP/CC than an FJR. Iridiums are probably a better overall choice for longevity. Did I notice a power increase with them? Yes! But I doubt it was because they were splitfires. It was likely because they were quality, NEW plugs.

To those who have run 15K+ miles on stock plugs, I hope you don't strip out the threads when you remove the old plugs. Spray some liquid wrench down there first! Trust me on this. More than 20K miles is blantently disregarding required maintenance. I know someone like this..."runs fine, must be OK". Funny how his shit breaks down all the time and nothing he owns runs well (I'm talking nice vehicles..Acura, Toyota, Honda, Yamaha).

BTW, does anyone index their plugs? I didn't bother last time, but will do it next time for grins if torque specs are close.

 

[JimLor]

Thanks to all - appreciate your comments and respect your experience. Based on what you've said and because I love tinkering, I'm gonna change the plugs tonight. Will also do a TBS and try the return spring disconnect to lighten the throttle. Thanks!

 

[Bounce]

Thanks to the eagle eyes of a couple of folks, I think the Spreadsheet of Periodic Maintenance is now working like it was meant to. Maybe it'll help someone who doesn't have the manual for what, when, and where.

https://www.bikes-n-spikes.org/maint/maint.html

 

[radman]

Indexing is fine for finding that last fraction of a horsepower on a race motor, especially on a rules motor, but like many racing parts/techniques, working that hard on a street motor rarely justifies the results.

 

[FJRottie]

Changing the plugs is good. Waiting too long like others said is bad.

Nothing lasts forever and your butt cannot tell the difference, but leaving the plugs too long will not be good for the engine/electrical system in the long run. Like Yamaholic said, it is like running a dirty air filter. The groundwire (the business end of a plug) can erode and cause misfires (I think Radman mentioned this).

I am only repeating what was said, because it holds true.

This is taken from the NGK website,

As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. As the gap between these two points grows, the voltage required to bridge the gap increases proportionately. Even the best ignition systems will be strained to supply enough voltage to completely burn the fuel. It is at this point, when fuel is being left unburned, that the time has come to change spark plugs.
Replacing worn out spark plugs with new ones (with sharp new edges) effectively restores the ignition system's efficiency. Misfires are reduced, power is restored, economy of operation is enhanced and emissions are reduced.

The best guide is the manufacturer's recommendation for your vehicle, as this particular service varies from brand to brand and model to model.

 

[radman]

While it can take quite a while for this to occur, and is not as severe on the narrow gap plug used on the Feej as opposed to the wide gap plugs found in automotive use, gap erosion can be hell on a coils life. Though I have no documentation to qualify this, I would estimate a halving of coil durability for every 15 thou of gap removed.

 

[FJRMGM]

I can't stand it any longer.

Plugs worn out at 8k miles, stripping threads because they are still in at 15k miles and halving of coil durability because the gap is a couple of thousandths of an inch wider?

Man, oh man, this thread is sooooo entertaining...

You guys have heard that auto spark plugs can now go way past 50K miles before they "need" replacing, right?

Precise, modern fuel injection, no-lead fuel and high-intensity ignition systems have changed the rules in case you haven't heard..

 

[radman]

I can't stand it any longer.
Plugs worn out at 8k miles, stripping threads because they are still in at 15k miles and halving of coil durability because the gap is a couple of thousandths of an inch wider?

Man, oh man, this thread is sooooo entertaining...

You guys have heard that auto spark plugs can now go way past 50K miles before they "need" replacing, right?

Precise, modern fuel injection, no-lead fuel and high-intensity ignition systems have changed the rules in case you haven't heard..

OK, ya got me. I lied like a MF just for attention. Damn, I hate getting busted.

rad, in the wrenching biz for 40 years.

 

[Constant Mesh]

Since the spark plugs operate in pairs on the FJR, the air gap on one plug affects the operation of the other plug in the pair. Plugs 1 & 4 are paired and plugs 2 & 3 are paired.

The high voltage circuit loop for each of the two ignition coils includes two spark plug wires, two spark plugs, two spark plug air gaps, and the aluminum (cylinder head) between the two spark plugs. These circuit components complete a series circuit with the high voltage winding of the coil (transformer). So, the condition of one plug can affect the operation of its paired plug.

I'd like to see the '06 FJR get individual coils mounted atop the plugs. This would eliminate the bulky spark plug wires, clear up the area above the engine head, and replace the two large coils near the battery with four small coils above the plugs.

With four coils there would cease to be any interaction between plugs.

 

[mech 1 twa]

Newer Honda AUTO plugs, service interval 110,000 miles. Platinum. NGK

Never had a problem removing them. NO carbon build up, no thread damage.

Apples to Oranges comparison, BUT .

Bike engines turn , on average double the RPM's of cars. Plugs wear out faster.

Some have coil packs, some distributors same plugs.

EFI systems run very clean.

 

[yamaholic]

Bike engines turn , on average double the RPM's of cars

Yep. Heck my V8 Toyota engine turns about 1500rpms at cruising speed. Rarely go past 3K, even when merging or towing in 4th (5th gear overdrive).

Also, most new automotive engines have platinum or iridium plugs. We have el-cheapos. Apples and Oranges.

All I can say if RTFM!

 

[radman]

03 Crown Vic Squad. 47000 miles. Driveability issue. Sp plugs removed by Ford as part of repair. Cost of repairs, $3,700 for renewal of cylinder heads with 3 stripped plug holes.

04 Grand Caravan. 23,000 miles. Wrong fuel (E85, 03 Caravans multi-fuel capable, 04's not) due to gas chip key program error. Spark plugs removed as part of repair. Cost of repairs, $2,300 to replace one cyl head due to threads pulled in 2 holes. Covered under warranty.

01 Windstar. 62,000 miles. Replace 2 cyl heads after 3 plug holes stripped, 2 weak holes questionable. In house, $3,900.

5 year antifreeze, 100,000 mile plugs, liftetime tranny fluid and final drive fluid on rear drives. Live the myth

 

[mech 1 twa]

radman you've had a lot of problems with cars!!!!!!!!!!!!!!!

I've wrenched on cars for 22 years, Honda's 16.

My own bikes about 12 .

Honda's Yah. Suz. Not an expert bike wrench.

Just my 2 cents.

 

[radman]

radman you've had a lot of problems with cars!!!!!!!!!!!!!!!
I've wrenched on cars for 22 years, Honda's 16.

My own bikes about 12 .

Honda's Yah. Suz. Not an expert bike wrench.

Just my 2 cents.

I run the shop for the UofM, we service roughly 500 vehicles, from golf carts to 320 Petes and Mack roll offs. Also 7 Copsickles, FLHTCI's. Prior to this, with Chevrolet for 15 years. You could say I've seen my share of odditys and problems. The above samples were all within the last year.