NGK BR9ES ?? On 2000 SLX

[Sirhc7897]

What should the gap be? I just checked a batch and they were all at .032. For some reason that doesn't sound right (maybe too much work and school has finally fried my brain...)

[Skexies]

My genesis 1200 had the BR9ES plugs.

Gap at .028, I ran mine at .024 because I was having problems with the drenched out oil in the system. Hella hard starts if I went from WOT to a bit of idle action.

Just for your info... I switched to the BPR8ES and ran .028 the ski was MUCH stronger in running.

[Sirhc7897]

See now that's something I've always been curious about...My 99 SLTX with the 1050 motor runs BR8ES plugs and I always wondered if I could switch...

Which is cooler the 9 or the 8? I always get that confused...

[Technical Support]

Lower is hotter. Here is the NGK Guide.

[Sirhc7897]

Ok so with my mods:bigger carbs, heads, FA's, waterbox, reeds, prop, nozzles, AAT, etc .. would it be safe going to a hotter plug?

BTW. That guide is extremely helpful. Thanks

[ February 26, 2003, 05:00 PM: Message edited by: Sirhc7897 ]

[Technical Support]

NO, if anything, colder. Read the porcelin to see if you have a good brown burn - that's your heat range indication.

[Sirhc7897]

Ok, so say the porcelain had only a hint of brown...colder / hotter

Also as a side note. Running with synthetic and premium gas (93 octane) my plugs have never had much color (again light brown only after quite a few hours). When I still used conventional oil I got the good brown burn you are describing. What, if anything does this mean?

Thanks for the help.

[Technical Support]

If you can get brown stay where you are. If you were all white, go colder. All black, go hotter.

I don't know what to say about the oil.

[Sirhc7897]

Thanks for the direction. I appreciate it.

[SeaLion]

Just a thought but maybe you guys are not aware of the accelerator pumps on the domestic engined skis? You can pump the throttle and it will squirt gas (like a primer) and you should be able to fire it right up.

[Sirhc7897]

My SLTX does that also. I never really had much of a problem with that on my SLX and now that I've switched carbs it's definately not an issue.

The throttle thing as SL mentioned was the only way to make the SLTX consistently fire up from that situation.

[UnoWho]

My 2002 Virage TX (1200 cc) uses BR9ES plugs. The factory Polaris service manual says to gap them at .024"-.028", I gap them at .028" and they are a light "chocolate brown" and it seems to run fine. Only thing I dislike is that it is a little hard to re-start after it has been sitting longer than 15 minutes or so.
My brother has a 1999 SLTX 1050 and he uses BPR8ES as his factory service manual says to use and he also gaps them at .028". His boat is hard to re-start too after it has been sitting 15 minutes or longer too. I have heard that this is a "Polaris triple cylinder thing "

Rick

[ March 01, 2003, 12:11 AM: Message edited by: UnoWho ]

[Skexies]

ok, my $0.10 .... (no flame intended)

Going "colder" does not directly save motors... it does potentially decrease performance capacity of the motor by trying to "patch other problem areas" that will in-turn reduce the loads on the motor but also potentially increase the problem of spark plug fouling or INCOMPLETE mixture igntion/burn. If you want to decrease performance to run your engine cooler and more reliably, you can do this a host of more appropriate ways including, assuring the cyl. cooling system is efficent, reduction of compression and potentially adjusting spark timing.

My at-length comments below;

Changing a plug temperature rating to change the color on the tip reading is a poor idea, if that is your only goal. Going to a hotter plug to avoid fouling is often a bandaid to fix another problem in the engine setup and is wrong if your spark plug is already running in the "optimum temperature range".

Spark plugs have a very specific range in temperature that the tip is efficent at cleaning itself from normal combustion cycles and also still properly igniting the fuel / oil / air mixture. Getting the proper tip opertaing temperature is one of the two proper goals of the spark plug heat range.

The second goal is the removal of heat from the combustion chamber to the cyl dome. Going "colder" to try and lower the operating temperature of the cyl to be safer may drop the temps below the "optimum temp for proper combustion". Kinda like cars that don't run well when they are first warming up on a very cold day. Colder isn't always better. If your engine is not cooling the domes properly or well enough in the first place... colder plugs may again be a bandaid to another problem.

NOTE: Additives in the fuel / oil can change plug color readings, as someone noted. Don't change fuel / oils when testing & tuning.

So... no matter what, your spark plug tip MUST remain in the 500 - 850 degree C range while in the "operating range" of the engine to operate properly. I say "operating range" because at idle or just off-idle is not what an engineer will expect the spark plug to deal with as much as running under high-load 3/4 to full throttle and running at WOT in a 45 minute race is a different temperature expectation than blipping a quick burst to 60 and back down racing your friend in a drag.

All the technical mumbo jumbo doesn't help out most of us, but let me relay what I have found. For those with the polaris 1200 starting problems, give the .024 a try. Doing so drastically made my starting easier. Less gap gives better spark in worse conditions... so I was guessing that going from WOT to idling around a bit, let oil pool in the crankcase that kept the plugs from properly igniting. I'd really like to know if someone has done the CDI hot-start issue fix on their ski, but still has the "sit and doesn't start" issue... if they switch to pre-mix if they still have the starting problem. That would say if the oil-pooling theory is correct, since pre-mix won't collect like raw oil will.

NGK's engineers recommend the BPR8ES [P for projected tip] for the pro 1200 (polaris 1165cc motor) as well as the Genesis 1165.

I've run projected tip 9's and 8's and the 8's are stronger by the rump-dynometer. Acceleration and top speed were both better when I swapped to the P 8's that NGK recommends. I still gap them at .024 for reliability... it felt like I was getting some mis-fires at .028 and the hard starts were harder.

I have also started experimenting with BPR9EVX plugs, which are fine-point platinum electrode tips and also re-presented the hard-start issue but have different ignition timing requirements to maximize their potential. They are what I used while running a race [45min @ WOT], I could tell I lost a bit of the low end when cold-starting and while waiting for the engine to come up to full-temperature for the first lap. After then, things seemed decent and very stable, but not as strong as the 8's did.

I hoped to play with some BPR8EVX plugs to gain that part that seemed lost with the 9's, but I have since added compression and ignition timing so I'm on the wall again. It is cold weather right now so I'm running the 8's, when it warms up I may drop back to the 9's and test them again with this setup.

REGARDLESS I am very sold on NGK's recommendation for the projected tip. "P" type plugs, regardless of whether you like the 8 or 9 temp range. I've done it and done it on my own craft, I know the change it made for me and that is why I'm recommending you check it out.

Between tightening the plug wire end-cap clips and the BPR8ES plugs gapped @ 0.024.... I got better power AND my fuel economy went up as well.

[ March 10, 2003, 06:10 PM: Message edited by: Skexies ]

[Wet Wolf]

I guess I can throw my .02 in here as well. If you are running a stock engine, then you should be running the plug (heat range) that the manufacturer recommends. If you are modding the motor, then you should run the coldest plug that you can that won't foul out.

There was a service bulletin from polaris back in 97 about the plug gap on the domestic motors and the factory recommended a .022 - .024 gap for the ignition systems. This gap setting solved alot of driveability problems on the domestic motors. I run the Cane at .024 and have no plug problems.

[Skexies]

8P's on left and 9's on right.



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[ March 20, 2003, 10:58 AM: Message edited by: Technical Support ]