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hey all...new to karting...i have done tons of reading and just a small amount of playing...so my new 'issue' is finding the correct plug for my MC101b...I have found conflicting reports on this but have it narrowed down to the autolite 411 and the champion j8j...the heat difference i can understand...but the 3/8" reach as opposed to th 1/2" i can't figure out...

tired of searching...want to ride...thanks fellas..

-chris hanly

called Rick.
you want 1/2" reach.
dave

wow...thanks again dave...ur the man!!
-chris

Remachined blocks, heads etc..... always check for clearance to be safe. Might also want to index the plug with copper gaskets.

Chris- Like Rob said, study the situation first. With the head off, install the plug and make sure it engages all the threads, but does not protrude into the combustion chamber. You'll soon be able to tell if heads take a 3/8 or 1/2 " reach plug just by looking at the hole from the outside.
Best 1/2 " reach plugs for Mac 91 and 101 are AC M 42 FF or Champion L4J or L78. If you have any other hi performance two stroke motors that happen to take a 3/8 " reach plug, NEVER use a J8J, as this plug is too "hot".
bill

good point Rob.
kinda forgot there are bummer and modified heads out there.
thinking about it i think some heads have a little flycut at the plug hole outside too.
i'm gonna repost your advise over on vintage as i figure it's more correct than mine and hopefully you won't mind.
dang cold is freezin my brain.
dave

You can also check clearance with clay or playdo & measure clearance. Better to be safe than sorry.

IF YOU DO hit the plug with the piston it's easy to break the ceramic. It will destroy your piston / head really quick.

I always like to turn everything over by hand to make sure nothing is wrong.

With this old boxes of mixed up parts we are fitting together you have to check EVERYTHING!

awesome input guys!!

Used the autolite 411 and turned it over by hand...didnt hear or feel any contact but i know that the piston head probably travels 1/8'' more when turning high revs...so rather than pulling the head I counted the threads...the 411 had the correct number as the previous j9c was one or two short...so that would definately explain pre-ignition...whoops!!! But in my defence..that is what the kid had in it when I bought it...he had no Idea what he sold me for $100...kart and engine...he couldnt figure out how to start it so he guessed it needed a new engine...a new plug and a carb rebuild later....I'm flying down the street..
just wanted to thank everyone...especially david for help throughout my learning process..
-Hanly