Spark Plug Help Please

[userj8670]

I have a 85 honda 250sx and pulled the plug on it today and it had a reddish/rust appearance on the insulator and side electrode. I looked it up and discovered the cause is from a substance called MMT (Methycyclopentadienly Maganese Tricarbonyl). Its an anti-knock additive in gasoline. Normally i run anywhere from 103 - 110 ocatane in it...is that bad? should i lower my octane? Currently i am running a NGK R DR8ES spark plug. I checked the gap tonight and it was 25 thousanths. I dont know what spark plug to run in my 250sx but this is the one it came with and i dont know if thats the proper gap. Normal gap for a car is 35 thousanths...should this be the same? Any reccomendations on what to do with my gas and if i should change the plug i run/gap ??


Thanks in advance

Jim

[WLL]

lower the octain.

[userj8670]

And what about what spark plug i am supposed to run and the gap?

[CrazyK68]

And what about what spark plug i am supposed to run and the gap?

NGK DR8ES-L gapped to .024-.028in

Hope this helps

CrazyK

[userj8670]

Thanks guys!

[oscarmayer]

i take it this is a race bike? if not, then why run such high octaine? I'm planning on pump 93 for my trike 185s and she's goign to have 12:1 comp. and slightly larger valves. (stock cam)

all i woudl do is look at tuning it woth jetting and the needle. the more comp and bore the richter each nitch you need to fo. I'm startign out at the middle notch instead of the factory top notch. i imagien i may have to drop it to the 2nd from the bottom for it to be right on the needle.

jetting I'm starting off with a 100 instead of the stocker 98. but i bet i'll have to run the 105 jet thought.

[userj8670]

No no no she is faaar from a race bike lol. Just a stock 250sx..i was told it was bored 20 over when i bought it but i cant confirm that. Why run such high octane? No particular reason, just a little more performance i guess and i like the smell I guess i will just go down to regular grade again.

[oscarmayer]

hehe i hear ya
yea i'd drop to 93. the X is 2cycle correct? (i forget sometimes if it is)
if so, i'd look at the denso iridiums they will last longer and provide more stable performance in the upper RPM ranges. (use them on my subaru Sti even though it's a 4 stroker)

I'd also make sure you just check your plug for tunning. you don't need anything fantsy to tune with. here's what I'd do on the 2-strokers.
change plugs and let it warm up. then bl;ip the throttle a few times but not to high and let it idle for about 5 min and pull the plug. read the plug coloring/ smell and yes taste (good tuners have no problems touchign their toung to a plug to taste the oil/fuel mixture ratios)

if it's really brown and tastes oily, then chagne the needle to a higher position and add more "gas" w/o the oil. (you may have too much oil in the mixture and this can also cause problems. best mixture i have found is about a 35:1 ratio for motors udner 10k rpm and 40:1 for over 10k rpm.

I would sue the NGK plugs for tuning and ocne it is settled, then use the iriduims.
gapping should be about .028-.030 is what i would look at uf under 10k rpm, if over then .025-.028

hope this helps.


also don't forget your going to have to change jet sizes for WOT tunning when you get the lower end done. so look at getting 2 jets sizes higher and lower than what you have now if possible. they are only like 45 a jet so that's only $20-$25 shipped for the jets.

[userj8670]

its a four stoker but i will drop the octane and see how that goes. its gapped at .025

Jim

[DeePa]

man just run 87, thats what they were made to run on.

[oscarmayer]

if it's a 4 stroker, then heck gap in my opinion shoudl be around .030-.034