Tips and Tricks

I have had a problem needed to replace the plug after ? rides because the bike just quits running. The plug looks fine during examination but as soon as I put a new plug in the bike runs fine. I've had trouble finding spark plugs in my area for this bike. The manual calls out using NGK 9ES? plug. Does anyone have any recommendations or experience using different plugs or is the stock spark plug best? The guy at the local shop recommended a different plug, stating it would last longer than the stock plug.

NGK BR9EV is the equivalent to the ES, which I think is harder to find. The local honda dealer here sold me a BR9EV and it looks the exact same.

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1980 CR250R Elsinore
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On the slow road to total resoration...

I'm sure you will get responses all over the place because the problem could be just about anything.

For instance, could just be that you are just not riding the bike hard enough to keep it happy.

You may want to switch to a hotter plug, something like a BR8ES?

It could be a deep rooted problem like low speed idle is too rich or coil is starting to fail. A hotter plug should let you limp by until you get a complete failure which is easier to diagnose. Just watch out for detonation with a hotter plug if you go that route.

While there could be some deeper mechanical problems you may a) be jetted rich and/or b) just not thrashing the bike hard enough. I had the same experience with the 1979 CR250R and did try some little adjustments with the idle and a NGK B8EV plug which is a littler hotter. However I did change back to the NGK B9EV and a new Mikuni carb which came with some proven jetting specs and I learnt how to cane it a bit and keep the motor cleaned out. How hot and high is it where you are, and what kind of riding do you do?

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Michael Stiles
AHRMA, CalVMX and SVRG #190
Honda CR250R Elsinore 1979
Honda CR480R 1983
Honda CR250R 1987

I do mostly dirt bike riding on trails. The elevation varies from about 3500 ft ASL(above sea level) to 3900 ft. The temp. varies from about 65 F to 95 F. What do you mean by "learnt to cane it a bit?" Does this mean the same thing as keeping the RPM's up? I have now find a source for spark plugs through vintage iron website.

I did mean keep the revs up and that is going to be difficult to do when trail riding. Your altitude and temp is very similar to here in SoCal and I am not surprised we had the same jetting/plug problems. If you stick with the stock Keihin I would locate 2-3 leaner pilot (58,55) and main jets (180,172,175), and a leaner needle and start leaning out the jetting methodically i.e. one change at a time. Start with 2 turns out on the air screw and the needle clip on the highest position...

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Michael Stiles
AHRMA, CalVMX and SVRG #190
Honda CR250R Elsinore 1979
Honda CR480R 1983
Honda CR250R 1987