Sj spark plugs

[IceRocket1286]

What plugs do the SJ's require? arent they like... b7es?


also, whats the oil/gas ratio? 40:1?

[Waste Land]

50:1
BR8HS (stock head)
BR8ES (aftermarket head)

[Keith]

If its the stock head than the service manual says to use b8hs or br8hs. Dont use the es plugs because they are an extended reach plug and may hit the top of the piston in a stock head.

Only use the es plugs on aftermarket heads that specify an extended reach plug.

Yamaha recommends 50:1. But most people are using 40:1 or 32:1. If the motor is all stock 50:1 would be fine. If its modified (more compression or high reving pipe) you will be better off with 40 or 32:1.

[Waste Land]

Edited mine....I put ES and HS nbackwards

[romack991]

HS is short reach (stock 701 head)
ES is long reach (aftermarket)

the lower the number the hotter the plug. i run 8's in my ski.

[IceRocket1286]

I picked up some br8hs plugs, runnin 40:1

fired my ski, sounds like heaven :headbang:

[madoyster]

BPR8ES works fine on my ADA head. They're a little longer according to Paul L ( JR Magoo's) and seem to work fine for me.

[bambooi]

Do you have to gap them?

[beachjunkey]

No. bambooi, you can get them from VB Watercraft, Cycle World, Sunrise, or order some online.

[bambooi]

i got them from boaters world. 2.49 a piece

[johnnyd]

my ski came with a twist head and B8ES plugs. should i switch to BR8ES? what advantage/disadvantage does having the resistance in the BR8ES give you?

[SUPERJET-113]

Here is a NGK chart from my Seadoo Racing manual CD.
There is probably something like this on the NKG website also.

[gj_fx1]

Resistor plugs cut down interference with electronics, so they are required on skis that have computer controled ignition and etc. I've never heard of any disadvantage to just running R plugs in everything..

[SUPERJET-113]

Any kind of electical "spark" generates radio frequency energy. Hell,the first radio transmitters WERE "spark gap transmitters". The spark gap transmitter was how the Titanic reported she was in trouble.

Anyways, the spark-gap transmitter is on the end of your spark plugs. A straight plug has a built-in antenna connected to this transmitter! The RF energy follows the center conductor up through the cap and down the wire back towards your CDI, conveniently located in the same box as the coil/coils. This RF energy might not destroy the computer but it will REALLY confuse it! The computer thinks it hears the trigger coil calling that it's time to fire the plugs again...so it does...firing the plug all kind of strange ways.

Adding a resistor, a special wire-wound one that is also a little rf coil called a "choke" does two important things. The coil in it acts like an RF blockage. The spark current gets through it fine...the RF trying to back up the wire can't. The resistor part of it turns the RF energy into heat, much like the resistor wire in your electric heater. No, the plug doesn't get hot...it's not much heat at all because the RF energy is only present for a few microseconds per spark. You can hear this energy if you carry a radio. It's a low pitched buzzing noise, especially on AM radio. Some cars are awful. So, the resistor in the plug, right where the trouble starts prevents the RF energy from following the wire out of the cylinder and converts it harmlessly into a little heat.

I know on Seadoos it will fry the MPEM if you dont have "R" plugs running. On Yamaha's(650,701,760 platforms) I have never noticed any problems. The first 650 SJ used BH8S... not much has changed with these ingitions... Its still good insurance. I run BR8ES on my 61X ignitions always.

[waxhead]

i always run resistor plugs as well
there is no reason not to but there is plenty to

[johnnyd]

ok cool, thaks for the explanations!! gonna run the BR8ES instead.

[Mile9c1]

BPR8ES works fine on my ADA head. They're a little longer according to Paul L ( JR Magoo's) and seem to work fine for me.

The P means the center section is longer (the electrode/ceramic piece, not the threaded portion). You can tell this from the chart that SJ-113 posted.

Anyway, those plugs can mess up your engine if it's not tuned for them. My friend runs those too, he swears they make more power... I'm waiting for his engine to blow up so I can tell him I told him so :27:

[SUPERJET-113]

What plugs do the SJ's require? arent they like... b7es?
also, whats the oil/gas ratio? 40:1?

:newbie: :sgrin: