Lets talk Plugs with Hi-comp and big bore

[BULLET99Z28]

Hey guys, Iv'e been doing a lot of searching on this site and r.net regarding spark plug choices. I have a fresh 310, 72.25 bore, 01 cr250 igniton, brand new ESR head w/ 28cc dome. I only have about an hour of ride time on it, but it should have roughly 200psi compression. Squish check in at .044". I am running turbo blue 110 race gas, amsoil dominator at 40:1. Carb is a 38mm A/S, DGH needle, 185/50 jets right now. For plugs, I am running BR8ES, but have BR9's also

From what I have been reading, with the higher temps of high compression and the added efficiency of the CR ignition, should I be running the BR9 plug to keep some of the heat out?

Iv'e only ran about 3/4 a tank of gas through it, but it fires right up, sometimes cold without the choke. Seems to run really well, no plug fouling, plug is kinda goldish,chocolatey color, and it runs right at 170 degrees when riding, never really going over that.

Thanks for any input guys.

[hartwill]

From what I have gathered from most every reputable engine builder they tend to stay away from resistor plugs. I have always been told to run either a B9ES or a B9EGV. I usually do tuning with the B9ES and switch to the EGV after so I am not fouling $7 spark plugs. With the cr ignition you may be better off running whatever Honda says to run in the cr250 as long as it's physically the same as an R's plug.

[89trx250r]

Yup I'm with Hartwill on this one the EGV plugs are awesome! They have a much smaller electrode which is supposed to help against fouling and provide a better spark.

[fearlessfred]

I would run the 9s and ck the ground stap to see that the blueing is close to the bend. if timing is adjustable,you can advance or retard the timing to move the bluing to the middle

[wilkin250r]

A resistor plug certainly isn't necessary. They are used on cars because a non-resistor plug has a lot of electromagnetic noise to it. Your electronics on your quad aren't nearly sensitive enough to be bothered by it.

When you say "should I be running the BR9 plug to keep some of the heat out? " I want to make sure you understand the issues. A "colder" plug won't actually make your engine run colder. The plug design reduces the PLUG temperatures, but it's not removing enough heat from your engine to make any difference.

The efficiency and strength of the ignition system doesn't affect plug heat range, but the spark curve can. I think the CR ignition is a hair more advanced than the stock ignition timing, which will increase the heat a little, so a colder plug might be a good idea.

[BULLET99Z28]

Thanks Wilkin. That's kinda the info I was looking for. Like I said, it runs nice n cool so far. Ill get a couple b9's and see how they look. I just don't want to "hot" of a plug with high compression.