Spark plug question

[vlxk]

So I'm getting closer to the rebirth of my RM250C2. My question today is, what's the big difference, advantage/disadvantage in the recommended B9EV spark plug and the B9ES that it ran on when I bought the bike?

It ran, although very poorly, when I bought it. Upon teardown and inspection, the left crank seal was in the bore crooked, the air filter actually had a bent nail in the hole on the post that holds the filter to the airbox. Believe it or not, the cylinder is standard bore but the ring gap was about .0025. Main jet is a 300, pilot was a 25. The fork legs had Florida Off Road registration stickers, so I'm assuming the pilot jet was changed because it was being ridden at sea level, and maybe the crank seal was creating a rich condition.

Anyway, the new Wiseco piston kit will be here Monday, then off to the machine shop for bore.

[vlxk]

I forgot to say, from an earlier post I have finished the Boge LTG rebuild. I found gas bags that are slightly larger than the originals that fit in the shock bodies. A guy in Utah, Adams Vintage Racing, specializes in TMs and RMs, built a new shaft to replace the pitted one, and I found a couple of 12x25x8 double lip seals to keep the oil inside the shock.

Everything seems to be working just fine, I'll get pictures posted soon.

[bazza]

Remember to warm up motor well with wiesco piston

[sleepy]

Don't know what your fuel is like in your part of USA but I wouldn't think a B9ES shouldn't cause a problem if it is in good condition. That is what I would use or a Nippon Denso equivalent.

[OverTheHill]

Hi, good luck with your re-build but [as has been said] be careful with the wiseco piston, give it enough clearance as per the instructions & run it quietly for a reasonable time [whatever that is]--till it feels right to [give it a damn good thrashing]. I hope i'm wrong-- but from the things you list as having found on inspection i sort of think it unlikely that they would have caused it to run 'poorly', unless a seal has popped right out [lean running on magneto side] or oily & lean on clutch side. Don't take too much notice of my ideas unless something rings a 'bell'--i just like throwing ideas out there. Another to keep in mind is [is] the exhaust partialy restricted from say slow rich running all its life or can something crumble inside the chamber & block the tail pipe--or muffler fall to bits & block the outlet. Another--have seen old filters crumble & get sucked [little bits] into the carb air bleed jets in the mouth of the carb. One more is the state of the reed valve petals, if they look ok then they should do the job but just look in-case a piece has broken off, also check the gasket on the reed block as have on--smaller suzukis [not on an RM] seen that gasket get sucked in along one side causing confusing carburation symptoms. Anyway--that's enough 'negativity' for one day sorry. [night here in NZ]. Hope she starts easy & runs well. Goodluck from OTH.

[bigk]

ES series plugs are the basics, I haven't had much luck with them (fouling easily) & prefer to use the EG series race plugs. EG's in the same bikes with the same jetting & no problems. I am experimenting with EM series (twin electrode for Mazda rotary engines) & have one in my modern 2T enduro (B7EM), not sure of any benefit, but certainly no problems so far, (been in the bike for about 1000klm's now).
k

[OverTheHill]

Talking plugs i bought a box of NGK BUE plugs because they were cheap [why else] not sure what you call them but think we called them 'surface discharge plugs' & look on the face of it the coldest plug in the world-- Mac 111 Kawasaki's had this type of plug early on. Anyway thought i'd try one in my old 360 Yam. I'll carry a spare plug & head off down the road & see how far i get before she oils up!!.

[Lozza]

So I'm getting closer to the rebirth of my RM250C2. My question today is, what's the big difference, advantage/disadvantage in the recommended B9EV spark plug and the B9ES that it ran on when I bought the bike?

It ran, although very poorly, when I bought it. Upon teardown and inspection, the left crank seal was in the bore crooked, the air filter actually had a bent nail in the hole on the post that holds the filter to the airbox. Believe it or not, the cylinder is standard bore but the ring gap was about .0025. Main jet is a 300, pilot was a 25. The fork legs had Florida Off Road registration stickers, so I'm assuming the pilot jet was changed because it was being ridden at sea level, and maybe the crank seal was creating a rich condition.

Anyway, the new Wiseco piston kit will be here Monday, then off to the machine shop for bore.

higher states of tune need a better plug, the thick centre electrode will shatter the insulator when engine is fully optimised

[SON]

If the RM is being used for VMX (not Flattrack) by an over 50 (age appropriate) rider then use a NGK B85 EG plug it is a Racing plug with a precious metal electrode and they are still cheap $16 in OZ