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Hi all. I finally got my '90 KDX going with new top end rebuild including new nikasil. It's really crisp and tight. I noticed in the manual that it says to run the NGK B9es. I always thought you were supposed to run b8es? I put a 9 in for break-in for a cooler combustion. Should I leave the 9 in? The UK models call for BR9es, is it ok to run the br in the American models? The r means resistor, right?
Also, at operating temp the bike with idle low after a short rev, but it'll raise a bit after 3-5 secs. Nothing real bad, barely noticeable. Maybe I'm just being paranoid. It runs great and has nice throttle response the whole way around. I checked for air leaks with some quick start. I even checked the flywheel side crank seal. No change in idle. Would float height have anything to do with that? Also, I'm still running the 48 pilot jet. Could that be the calpret?
Oh, one more thing. I'm missing the coolent reserve tank. Is it safe to run it without that, or should I be grabbing a new one. Will it suck air through the coolant system without the reserve tank?


Sorry for all the Q's in one post. Just trying to kill 2 birds with one stone. Thanx.

run the 9. it is okie. just gap it correctly.

you will suck air if the system heats to the point of purging. if it starts spewing coolant, when it cools it will draw air into the radiator. dont overheat the bike and you will be fine. refill any purged water asap. i have ridden a couple bikes that dont have overflows. if wont kill the bike to run without it, but it will if you let the system fill with air. just monitor until you get a replacement. or ziptie a soda can on

better off running an 8

Mr. Wibbens wrote:better off running an 8

Yep!

On my last KDX, about 15 years ago, I put a new top end in it and for some reason ran a 9 in it for the break in. After about 3 years I felt bad for the plug and put an 8 in. I couldn't tell the difference.

These bikes are very compliant to what ever they get. I use a 8 but what ever you think you need will be fine!

8 produces hotter combustion. That's why the cooler 9 is recommended for break in. I always ran an 8 after break in, but in the manual it says that it called for a 9. I think I'll shoot it with a temp gun with both plugs and compare the temp differential. I'll let you's know the results.
I got a coolant reserve tank last night. Does anyone know where the bottom input nipple hooks up to? I can see it hooked up in the manual but can't see where it goes or if it's plugged off. Is it plugged off?

Terrence Sprocket wrote:8 produces hotter combustion. That's why the cooler 9 is recommended for break in.

the heat range of a plug affects the temp of the plug at the tip, not the combustion.

I found a quick link with more info for anyone who can't sleep - http://en.wikipedia.org/wiki/Spark_plug