Date: Sun, 30 May 1999 09:26:26 -0400
Subject: New Rider Info
From: Chris L Johnson 


On Sat, 29 May 1999 19:33:23 EDT Skropp1028 "at" aol.com writes:
>Chris,
>
>Thanks for the reply...I'm not sure my conscious will let me run 
>mixtures that lean !!!    It sure should run well that way anyway.

This is a common misunderstanding about trials motors and lubricant
amounts.  For trials you need much less that for motocross, road racing,
etc.  Also a misunderstanding of how 2-strokes lubricate themselves.  Oil
is not used at a constant rate, but rather get's "stored" on all the
parts somewhat in the bottom end, so when you open her up wide, you'll
blow up more lube into the combustion chamber then when you putz around -
which is when it builds up.  So much less oil is needed for trials
because you rarely hold it wide open for more than a few seconds, if
ever.  Evidence of this priciple is that after letting the bike sit
overnight, you have to "clean it out" during the next warm-up.  You are
scavenging up (coughing up) the oil that coated the components during
your ride, and that gravity pulled down to collect in the bottom of the
cases.  Too much oil is like pneumonia.  You'll have a phlegm mobile!

If a wide-open, world-class rider can feel "comfortable" at 100:1, so can
you.  But if you want to run 32:1, go ahead.  You'll just fill your
muffler up with oil and contribute more to pollution.  Use 80:1 if you
want to feel better about it.

>What does the higher compression do to performance at trials RPM's ?

A bit more snap off bottom, mostly.  Te reason I suggested you remove the
head gasket from the 350 is that Yamaha really blew it on the squish band
specs.  The excessive gap between the piston perimeter and the head
contributes to the tendency for the 350 to ping and rattle when it gets
hot.  You'll get a bit more compression by removing the gasket, but
you'll probably not notice it much.


Chris Johnson, Director of Engineering
College Park Industries, Inc.
papazit "at" juno.com (home address)
chris "at" college-park.com
www.college-park.com