Yamaha Enduro 60hps Burning Up Spark Plugs

[99yam40]

I would wait until you can confirm that unit works well on outboard motors, like I said before some do not like the electronic noise put out by those CDI systems and do not work correctly.
The only comments that I saw from someone that tried it , was not working well with outboard

That is why I was asking Rodbolt about ones the work well

[FabricGATOR]

A few thoughts...

When I first read the thread, I acknowledged that I have had similar experience in the past with my 80's 9.9, 15 and 70 hp Evinrudes, our late 60's 40 Johnson would also loose its umpfh and a fresh set of plugs would fix it. I always attributed it to the marine environment and or possibly the two cycle oils. Lawnboy lawnmower's (also an OMC product) would also need a fresh plug in the spring, although the electrode showed little erosion.

Champion makes a spark plug tester that has both a media blaster and a high voltage / under pressure testing aparatus, among others. Simulates the spark firing under compression.

See examples:

Spark Plug Cleaner & Tester Manufacturer & Supplier, AUTONICS MACHINES (INDIA), India

Spark Plug Cleaner and Tester,Spark Plug Cleaner,Spark Plug Tester Manufacturers,Delhi

Products > Airframe & Power Plant > Spark Plug Tools :: USTOOL.COM

The code.
B8HS10 is a 14mm thread plug of moderate heat range with a 12.7mm (1/2") thread reach and a standard 2.5 mm electrode the 10 stipulates that it comes pre gaped to 1mm (0.40)
*NOTE "Heat Index" is not a temperature that they fire at as is commonly mistaken. Heat index is the spark plugs ability to remove the heat based on the design and length of its ceramic nose. If the plug is too hot, it will not dissipate the heat quickly enough and you may have pre-ignition or detonation.
These are not resistor plugs, if they were it would be coded with an R prefix before the heat index eg. BR8HS

I have seen my plugs, that have lost there fizz, in the spark tester/cleaner where under pressure, they did not spark same as open air. I have seen a brite white irregular like a sparkler white spark. Also have seen tracing down the resistor due to carbon tracing or insulator contamination.

For me in the 80's the cure was to scrap the Champion sparks and NGK or AC Delco was the cure. Pretty sure we had a bad batch of Champion plugs on Long Island, NY at least in my specified requirements. But I like Champs and despite my previous experience, I still run them today in some applications.

I suggest trying a different spark plug supply. Try the champions: Cut n Paste from Yamaha_Tuneup_specification.pdf from the top "sticky" from this forum:

Tune-Up Specifications:
Spark Plug - NGK . . . . . . . . . . . . . . . . . . . . . . . . . . . . B8HS-10
- Champion . . . . . . . . . . . . . . . . . . . . . . . . . . L78C
Plug Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0mm (0.039”)
Ignition Timing @ Idle . . . . . . . . . . . . . . . . . . . . . . . . . . -7° +1°
(‘99) -2° +1°


Possible spark plugs for NGK B8HS-10: (I cut n paste this from the web so do your own research)

AC Delco 41F
Accel 156
Autolite XS4092
Autolite 4092
Bosch W4AC
Bosch W3AC
Bosch stk 7528
Champion L82C
Champion stk 811
Denso W24FSU10
Denso 6073
Denso W24FS-U10
Denso 6047
Denso W24FS-U
Denso TR24-10
Denso stk 4038
Motorcraft AE1C
Prestolite 1,40E+002
Splitfire SF409C

If while working, replacing, cleaning a sparkplug and you accidentally drop it on the concrete floor.... drop it a second time. Drop it right into the trash can. The point being that a shock may cause a fine crack in the insulator and it may only show defective under heat and pressure of being in operation. It may test good right away and then fail in five, ten hours maybe never. So then you have a miss, take em out and clean/test and they all test good again, until the get hot. How frustrating chasing an intermittent problem that is only evident in operation but does not reveal itself when bench checked. Drop it once, drop it twice!

Listen to RodBolt. To the layman, those plugs look like they were recently replaced and new. Because they are. but his trained eye see's that there is irregular pattern on the insulators that explain them loosing there Fizz (contaminated insulators) probably allowing high voltage to bleed through or down the insulation instead of jumping across the airgap. Possibly a different vendor's insulator formula may be more impervious to this contamination in the fuel, oil, ethanol treatment . Maybe your engines are being run within or too close to the Bermuda Triangle...

[FabricGATOR]

One more thought.

In researching it further, I found some literature from NGK: its a product catalog from 08-09

Three steps to installation:
1. Determine existing spark plug
2. Find the alternative spark plug in the table*
3. If necessary, reduce the electrode gap by 0.3 mm maximum

*Please note:
For LPG units based on the venturi system, spark plugs one heat range higher must be used
(e.g. BKR5E => BKR6EIX-LPG). (N/A LPG = Liquid Petroleum Gas - like a fork lift or generator)
For vehicles already factory fitted with high quality NGK platinum or iridium spark plugs, no other
type needs to be used. If necessary adjust the electrode gap.

Having read this and reviewing what I compiled in the previous post I think I might have a cheap easy solution that can be tried right away. (Roddy's probably gonna tell me that I'm whack)(and I respect that, I am definitely thinking outside of the box)

Electricity is lazy, always taking the path of least resistance. In this case, it is probably tracing down the insulator because it is easier than spanning the airgap. I/A/W the NGK literature, it is acceptable to close the gap UP TO 0.3mm closed. So from 1.0 mm we can close it UP TO 0.3 so a minimum gap of 0.7mm or .027

Conversion Charts
0.7mm = .027
0.8mm = .031
0.9mm = .035
1.0mm = .039

Try closing the gap on the plug and make it easier for the spark to jump the airgap than get outside the insulator.

I'd try 0.31 and see if it made a difference. If it works, open it up to 0.35 and see if you still can maintain an acceptable lifespan for the plugs.

I'd also consider indexing the plugs if applicable. Some race geek friends would mark the open side of the sparkplug gap on the flats of the outside of the plug. This way they could see which way the gap was facing when properly torqued in the cylinder head. They would have it face the center of the combustion chamber volume, thus believed that they were getting more through fuel burn or something. They would mark all the plugs with a sharpie marker, then keep trying them in different cylinder holes until they had a combination that they were happy with. Theory being that each threaded plug hole was indexed a little differently as were the plug gaps when mass produced. so in swapping and trying different combinations they would eventually get the gap facing the way they liked it. I'm not familiar with the volume, shape, or hole placement so I might be blowing smoke on this plug indexing whooey.

Oh yeah, People, please use a torque wrench when installing the spark plugs. I believe the torque is 18 Ft Lbs or 25 Nm. I can't stress this enough that unless you do this everyday as a technician, you probably don't have the calibrated wrist.

I work with fools that want to make everything diver tight and what a mess that is. (diver tight is when you torque it until it strips and then crack it off an 1/8 turn) These jokers (meaning to do a good job) ruin hydraulic fittings by over-tightening(they don't want it to leak- Good Job!), that then need to be overtightened the next time they are used in a different component, thus deforming more fittings... and on and on and on.

Have fun, let me know....

[99yam40]

These are not resistor plugs, if they were it would be coded with an R prefix before the heat index eg. BR8HS

did you not see what he wrote or look at the pics

NGK BR8HS-10is what he has in #1 post

[rodbolt17]

a BR is an acceptable substitute for a B, not the other way around.
I would still want a Kv test.

something is wrong with the setup and I dont think its plugs.

you may try a B or BR7 and see what happens.

[madharchod]

well guys its like guess work for some of you Like Rod-bolt iam also an expert but wouldn't state my work practices as the law forbid me now even iam retired but these motors i know like back of my hand as i deal with them every day as this is what is mostly used in Fiji ,so please try a new set of spark plug from some other place and your problem solved no need to get too technical and confuse the poor bloke and as for some people Australia Yamaha does not import these motors as they are made for third world countries as they need something bullet proof,ie value for money not like some of us we change new motors before the warranty runs out so to say we can afford

[Bonefishr]

Yeah....don't confuse the poor bloke. Just received a new box of 10 plugs from Nassau and another 25 are on the way from the states, should be here tomorrow. That should last me a couple weeks....kidding. Maybe I did have a bad batch or two.

The plugs I'm using and what the mfg calls for are BR8HS-10. Years ago I remember using some B8HS-10. I don't recall any performance issues with the B8HS-10, there may have been some that I didn't attribute to the plugs. I don't understand plugs and why there are so many. If I stuck either one in my ear and you pulled the rope I probably wouldn't be able to tell the diff.

The RPM/kv meter will also arrive tomorrow. I know you advised against it but I had to pull the trigger quick and get it overnighted. I'm feeling lucky, hopefully it'll work. It's was the only one I could find at such short notice. If I don't test them now I won't be able to get back to this until this coming fall. I close for the season and lock everything down in three weeks.

I'll post the RPM and kv results in a few days for your evaluation.

[Bonefishr]

I'm not sure what you're looking for but here are the numbers.

Motor one, on it's second set of plugs for the week. It checked out this morning with the top cylinder reading hotter than the bottom two with peak kv around 30 and holding around 25-26ish. The bottom two cylinders tested at peak kv of 26 and holding between 20-22. I just rechecked the same motor with the same results BUT then it started to sputter and was slow to react when hitting the throttle and not wrap out. The two bottom wires dropped to between 14-16. The top cylinder dropped to a high kv of 4 and a low of 3. I put a new plug in the top cylinder and then they all read mid 20s. I'm ready to take a hammer to this motor.

Motor two checked out with the top wire in the high 20's and the lower two in the mid 20's.

Motor three is running perfectly but recently did ruin a set of plugs in one day. The new set is on day four and still working.The kv checked at mid 20's, all cylinders. This motor was in the water so I checked the RPM under normal weight load. Wide open it's running at 5900RPM, too high. The current prop is a 15". I'd like to slow it down to below 5500. A 19" should slow it to 5100 RPM.

I do have 19" on the forth motor. It's been a month since I put plugs in that motor.

So....maybe it's over-reving or a bad batch of plugs....or none of the above. Motor one has me confused unless the guide is running it at full throttle all day. It's possible, he's been begging for a faster prop. I'll bet he's been racing number four home and getting his a** kicked.....that's why he wants the faster prop.

[99yam40]

I do have 19" on the forth motor. It's been a month since I put plugs in that motor.

Sounds like this motor is doing a lot better than the others. Have you kept info on how often this one is having problems with plugs?

[rodbolt17]

20n Kv is WAY WAY high.
check the secondary coil resistance carefully.
also check the carbs.
4
kv is a tad low.
you should see 5-7 Kv on that rig.

but see, the equipment is already verifying you have an issue that is NOT a spark plug.
fouling plugs is a symptom of an issue,not an issue.

[Bonefishr]

Rod....this particular kv tester can only check kv by holding it on the spark plug wire. It's inductive and somehow reads the charge running through the wire. I'll need to buy an new ohms meter to check primary and secondary resistance. My last ohms meter had the batteries corrode in the unit.

The kv on all the motors average between 20-22 with peak kv around 30 on some coils. It seems to change at random. How do I get the voltage down?

I'm not sure what you want me check on the carbs. Basically they're all new. I did have one carb that was leaking gas and flooding. A couple taps with a screw driver knocked the float loose and fixed the problem. There's only one adjustment screw and they are all set a 1 1/2 turns open.

Also...I'm still a confused about why the one coil that was reading 3-4 jumped up to 20s after I installed a new plug. Now, on the same motor, the middle coil in reading 15ish with the top and bottom reading 20s. I'll bet if I change the middle plug they'll all read the same.

99yam40....Yes, the motor with the 19" prop seems to be doing better than the others. I haven't put plugs in that one in quite awhile. I was keeping record of spark plugs changes but I've been doing it so often I've lost track.

[rodbolt17]

my snap-on Kv tester is inductive as well.
it measure the firing voltage in THOUSANDS(KV) of volts.
typically on a normal running engine with a single electrode gapped at about .040 you will see between 5 and 8 Kv.
thats 5000 to 8000 volts.
as the fuel mix leans,engine temps or combustion pressure rises it will make more voltage to arc.

as I mentioned before,lectricity is very lazy.
worse than me.
that ign coil will ONLY ever generate JUST enough to arc and not a volt more.

which is why I get so tickled watching folks waste money on "flame thrower coils and plugs"

there are a few systems,typically the coil on cap models, that run a Zener diode in the circuit.
the F250 to F350 are examples, if the fire at all it starts at 32Kv.
I can attest that that system will arc an 11/16ths gap and thats as wide as the spark tester would go.

surface discharge plugs,typically found on mercury motors will arc at 15-20 Kv.
the twin electrode EKU style plug will typically arc at 10-15Kv.

this comes from observing my tester for better than 20 years.
I use it on auto's,boats,lawn mowers.
anything with a plug wire.

that C60 is capeable of about 40Kv,however it typically operates at about 5-8KV.

thats why I asked about coil secondary resistance.

if you dont belive me either use an adjustable gap tester or open and close the electrode gap and watch the Kv follow.

[Bonefishr]

Very interesting.....The BR8HS-10 is gapped at .35 out of the box. Spec for this motor is .35 to .40. So if I close the gap to say .30 the kv will come down? Won't that cause an early spark and backfire?

I noticed in my owners manual that I can also use a B8HS-10. What is the purpose of a resistor plug vs. a non resistor?

Would you suggest opening the carb jets another half turn or full turn? I have them at 1 1/2 turns because that's how they arrived.....and I'm paying 6.50 a gallon for gas and oil. I rather not blow unburnt gas out the exhaust. I remember running them at 2 1/2 on the old motors. The plugs aren't really fouled at the current setting, a little more fuel wouldn't hurt.

[rodbolt17]

the -10 indicates its pregapped at 1mm or roughly .039.
on your engine the only benifit to running a BR is if you have radios and the B plugs make noise on them.

[Bonefishr]

I can barely force a .35 gap gauge into the gaps.

I'm going to switch to the non-resistor B8HS-10. The resistor BR8HS-10 isn't necessary and something else to go wrong. I found this little piece of info from here Resistor Plugs, Wires, and Related Issues ..... The benefit of doing so is two-fold. First, there is obviously one less thing to go wrong. Ignition secondary resistors are usually carbon-based, and therefore deteriorate rather quickly. Eliminating the resistors in these systems simply eliminates them as a maintenance item. Second, removing the secondary resistance often increases potential ignition coil output, because it frees up more of the coil’s voltage reserve to be applied to the spark plug. The real-world gain is the ability to use a larger spark plug gap, with the attendant increase in combustion efficiency that is often realized as quicker starts, smoother idle, and better throttle response – most of the same things high output coils offer, but without their cost.

Oddly enough, I also have an idle problem. The RPMs are good but they still stall. Maybe this will solve that problem too.

I'm going switch to the B8HS-10 and regap them to .40. Change the props to 19" and open the carbs a turn.