Can a plug pack up just like that?

[92_CR250_fmf]

Hi.

Recently bought a 1992 CR250 which I use on weekends for track work but mostly woods riding.
I don't know too much history about the bike, but know it has a new cylinder & new electrics.
It also has an FMF (gold series) pipe.

Bike is great, I love it & it starts on the 3rd kick from cold everytime & is so easy to start
when hot it's untrue, but I had a problem this weekend that I hope you lot can shed some light on.

Bike was running great all sunday, me & some mates were riding up & down some really tricky hills & we had to lay our bikes down quite a few times due to the steepness & our inabillity to ride up them!

Got halfway up a hill, came unstuck & had to lay it down again, but kept the motor running. Dragged
the bike round, got back on & rode down, but the motor then died, fired then died again. We towed it to try & restart it, but it was a no go.

Got it back home & found no spark from the plug, but lots of juice from the lead (got a big shock!)

Put my mates plug in & it fired 1st time. Is it normal for a plug to fail just like that? It looked fine in it's appearance (not melted etc) if a little dark, but nothing untoward.

Plug is an NGK B8EG. I have ordered a new NGK B9EG (higher heat range) as recommended by my dealer in the hope that it won't fail as dramatically again so far from home!

So tell me, is it the plug & it's normal, or have I other issues?

Cheers in advance,

Gwaredd (UK)

 

[Rcannon]

You actually bought colder plug. If this is the cause (wrong heat range) it should happen with the 9 faster than with the 8. To go hotter, you need the 7.

 

[jmics19067]

I can see your problem happening quite easily. You lay the bike down going up a hill, the needle and float think the carb bowl is empty from the wierd angle. The carb overflowing and raw fuel is filling up your airboot/filter when you turned the bike around and headed downhill the fuel went into the engine flooding it out and fouling the plug. Bring a spare plug and a wrench next time you go riding would be the only thing I would be concerend about. Sometimes you can get away with holding the throttle wide open and kicking like mad for a bit to clear out all the excess fuel in these situations.

 

[Joepro9]

I actually have killed 2 plugs before on my cr, both eg's, the reccomeded plug, but i switched to the b8es, (r or non r) and havent had a problem since.

 

[92_CR250_fmf]

You'r right. Just checked the NGK web site & 2 is hottest, 10 is coldest. They recomend a hotter plug if the standard one is getting wet fouled, as is burns carbon etc quicker, but a colder plug if running at high RPM for long periods. Hmmmm. I think I was just unlucky & flooded the engine by keepiing it running & then wrecked the plug somehow.

I think I'll send a B9EG back to my dealer & swap it for a B7EG, try them both & see how I get on. I will also explain the heat range to him, as he doesn't seem to have grasped it very well.

Cheers,

Gwaredd.

 

[dthoms]

Like someone else said I have had better luck with the B8ES plugs, I would be careful, go to a hotter plug. I wouldn't do it after just one failure. It's very possible your bike just got loaded up because of the crash. What color is your plug burning? I would re-jet if a B7EG made a difference. I have seen where a plug just wouldn't fire for no particular reason. One thing that is nice about the B8ES is they are cheaper than a B8EG, and I think they are less prone to foul. I like them because I seem to give away more plugs on the trail then I use, so at $2. a piece I don't feel so bad. One time a guy offered me his new goggles for a plug although it was tempting I turned them down and told him what my truck looked like and where I had park, and when I got back to my truck he had lift 5 bucks for me, that was nice. I've owned a CR250 of about the same vintage and it was one of the best and one of the worse bikes I ever owned. I bought it used and every time I took a bolt off it was stripped, I bet I had 20+ heli coils in the bike before I got rid of it.
Good luck
DT