mikstr

The thread on spark plugs got me thinking... do those of you running high compression VTRs run colder plugs? My JE pistons are not installed yet (decked heads raised compression slightly but not enough to really matter) but to those who are running JEs or Mori pistons, are you still running OEM plugs or have you gone down to slightly colder plugs?

thanks in advance

nothing

each step colder plug is generally for increases of 50hp at a time or 70 to 100* C

killer5280

I'm running stock plugs, but one step colder is probably a good idea.

mikstr

Problems with colder plugs, in my experience, typically arise when the engine is cold, when the risk of fouling is higher. However, as the JE pistons I`ll be running are forged, I will have to be more cautious with warm-up anyhow (something I am always careful with) so the risk of fouling should not be an issue. A colder plug, I would think, would be a good move given that I`ll be running the motor with Stage 1 cams, gas-flowed ports, full exhaust, custom velocity stacks and significantly higher compression (the main potential culprit). Think I'll do it.....

nothing

I would just go for it, worst case scenario you gotta switch back...and you're out $5. also where did you get all these internals for our bikes?

mikstr

My bike has been a work in progress for a few years now. A good portion of what I have has been purchased on eBay or from fellow forum members.

Circuit_Burner

On our racing 2 strokes we ran B9EV instead of recommended B8EV OR B7EV.
Run as cool as it will take and still burn clean.
On our pro-circuit ported engines, B7EV would put pits in the piston crowns.
The higher the number the cooler the plug.

mikstr

Most two-stroke snowmobiles run 9's, and a few have run 10's (I had one for a few years, a 600 cc triple). I'll have a look around for a colder plug then....

mikstr

I did a few searches and found nothing colder in the VTR's spark plug type. Guess OEM it is....

JamieDaugherty

Don't you mean $10 per plug? The VTR plugs are expensive.....

nothing

Oh, well dunno since these colder ones actually aren't going to be "VTR plugs." But I bought 4 colder ones for my car and they were $2.79 each and that's 2 steps colder

JamieDaugherty

Yes, but the plugs to fit the VTR are not like the ones in your car - they are special. Colder, hotter, or standard they are all expensive.

VTRsurfer

Colder plugs should only be required if you're going flat out on the track, under constant heavy load. I've changed mine slightly past Honda's recommended mileage, and they still don't show any visible wear on the electrodes.

Higher number=colder plug works for NGK and Nippon Denso. American plugs are the opposite. (but who would put American plugs in a Japanese bike)