Bad Plugs- very strange

[BULLET99Z28]

So I bought 5 b9es NGK for break in and tuning. Well, when I got her fired, she kept wetting the plugs after a few minutes of warm up, so I dropped from a 52 to 50 pilot. Kept wettin the plug, so I kept popping new plugs in with the 50 pilot, same thing. Today I got my new OEM coil in, installed it, Bam, cured it. Well I still have those new plugs, they are dry and clean, So i have been using them just to incase I foul a plug while breaking it in, and I may go back to the 52 pilot, and bump the main from a 178 to a 180 or 182.

Anyway, the bike has been running fantastic just easy riding and letting her break in. But 3 of the plugs have come apart. I mean the porcelain is separating from the Steel hex part of the plug. After a couple minutes, it just gets boggy. Pull the pug, sure as shoot the porcelain is loose, or the electrode has begun to slide up inside the steel hex part causing the gap to widen WAY out. 2 of the 3 you can spin th porcelain. The ground strap is not getting dinged by the piston, no physical damage at all, and the color leads me to think I need to richen up. Has anybody ever seen this happen with plugs? I got all of them from the same store at the same time. The motor starts right up, idles nice, runs smooth,etc.

[BULLET99Z28]

I should add the motor is a CT mid ported 310, radvalve, 38mm airstyker, full FMF fatty exhaust, Uni filter w no lid. I havent done a compression test yet, waiting to break in a lil bit more, but it feels like it has a ton of compression. Running 110 turbo blue mixed at 32:1 w Yamalube.

Just can't figure out why my plugs would be coming apart like this. There is no visible damage at all, it makes me think it may be a manufacturer defect, the porcelain literal shakes back n forth in the hex, very strange.

[Jesse1980]

your using 'Yamalube' thats your problem

[BULLET99Z28]

I used Yamalube for 8 years in my flat track Pilot motor, and that motor ran wide open 20 nights a year, 3 races each night, and won me several track titles. In those 8 years I rebuilt the top end 1 time, and it would spank rotax powered pilots and open class quads in practice sessions. I don't think Yamalube is the problem while I'm breaking it in, and has nothing to do with the plugs coming apart, but thanks.

I went to a different Parts store today, got 2 NGK b9es, 1 NGK b8es and 1 Champion equivalent to compare. I ran the NGK b9 for about 10 minutes, plug stayed intact, and it has a rich color to it, but runs really strong. Maybe I had some defective plugs? Can I wrap the threads with sealing tape to help with vibrations? I already use a small amount of anti- sieze.

[DnB_racing]

Originally posted by BULLET99Z28
Can I wrap the threads with sealing tape to help with vibrations? I already use a small amount of anti- sieze. no dont use any thing that would act as an insulation and cause a poor ground connection

[BULLET99Z28]

A guy at work who has a friend that is a honda mechanic said to wrap the threads, but that made no sense to me, just as you said, poor ground. I always have used a weee bit of antisieze especially w aluminum heads. I have never seen a 2-stroke vibrate plugs apart.

That honda mechanic also said it could be detonation, I don't think so. I am running the stock short rod lower end, Wossner piston, and 27 cc dome, Comp should be right around 12:1. And like I said, running straight 110 in it. It runs great. When I had the clutch side all apart, Counter balancer was lined up correcty as well, never pulled it, just made sure everything was good and tight when going through the clutch.

[wilkin250r]

I'm thinking you just got a set of bad plugs.

I've seen motors that vibrated so badly they broke motor mounts, but never spark plugs. And I have also seen spark plug where the porcelain came loose, and that motor didn't vibrate hardly at all.

I could indeed see how detonation could cause it, the shockwave caused by detonation is pretty severe. But you would probably hear it, and if you looked into the motor, you could probably see other signs of detonation if it was indeed occuring. With a little bit of work, that one is easy to rule out.

I don't think you need to do anything fancy to reduce vibration, as far as I know, nobody else needs to do that. I think you just got a set of bad plugs.

[BULLET99Z28]

Thanks Wilkin. I got more from a different store, first 1 seems to be ok. This may sound dumb, but I may have been overtightening them with my wrench. But I have never broke plugs in cars, and I have built some nasty chevy motors in my camaros before, usually tighten them down pretty good. Now I can start to get some good plug readings, the plugs were no doubt letting compression by and sucking air back in. My lug cap keeps wanting to back off now, probably wore out, might try and crimp it down or replace the cap.

Edit- I did a comp test today with a Snap-on gauge, but it didnt reach in near as far as the plug, still got 180psi, and I have maybe 1/2 a tank ran through it so far, so I def should be ok, and pulled the stator cover off, its all good, clean and nothing is modified, all parts looked good. Def don't feel its from detonation.

[wilkin250r]

Originally posted by BULLET99Z28
Thanks Wilkin. I got more from a different store, first 1 seems to be ok. This may sound dumb, but I may have been overtightening them with my wrench.

Correct me if I'm wrong, but Chevy spark plugs use a taper seat, correct? While your 250r spark plug uses a crush ring, so you can't really compare the two.

You shouldn't need to tighten your spark plugs down too much on these engines. The honda spec is 11-14 ft lbs, but that's for a normal stock engine. For higher compression, you might want to hit the upper end of that range, I'm thinking 15 ft-lbs or so, and that still isn't too difficult to achieve with a normal wrench or socket. These are just aluminum heads and the threads aren't very big. You don't want to risk stripping the threads out of your head.

[BULLET99Z28]

New batch of plugs holding up fine. I replaced the loose fitting plug cap with a NGK cap, checking torque on plugs, bike running great through 1 tank!