so the top end i did to illustrate this write up finally wore out. the hour meter broke about 10hr in and i never replaced it, but i would guess that this top end has 300+hours on it, and that is being conservative. i have beat the hell out of this motor. its seen a few races, a 10hr GP, lots of mx, and a ridiculous amount of single track, as well as lots and lots of sand via the desert washes here in AZ. jetting was usually spot on but sometimes overly rich when i went up in elevation.
the only reason i looked into the motor is because it started spooging like crazy. i assumed the reeds were bad(they were) as i hadnt even looked at them since i did this write up. it still ran pretty good and had 140psi cold compression. i pulled the pipe off and noticed the PV was kissing the piston. the linkages wore just enough to drop the main valve into the cylinder just a few thousandths. that prompted the tear down.
what i wanted to show in this post is how well the break in procedure described in the write up seated the rings, and how well a diet of strictly 32:1 maxima 927 castor oil has worked. there was only one 3-4 hour ride where i forgot my oil and had to use generic wal-mart 2 stroke oil, still mixed at 32:1. other than that, every minute this engine ran was on maxima 927.
the piston. this is exactly how it came out of the motor. i dint wipe it down with a rag or anything. absolutely no blow by. 0. the carbon deposits on the top of the crown are bizarre, although i have seen patterns like that in other 2 strokes. the areas where there is no carbon are whistle clean.
if you look really close you can see where the left edge of the main valve just started making contact with the piston. its the smeared spot just below the crown where the carbon was trying to invade from the increased wall clearance. i didnt measure the piston diameter because the skirts are clearly worn out. especially on the intake side where the transfer ports are located, they wore a shallow slot into the skirt.
heres the other side where the main valve was making more contact. although it appears otherwise in the pic, the rings were free and not stuck.
cylinder head. this is how it came off the bike, again, i did not clean at all or wipe with a rag. the deposit at about 2 oclock i wiped with my finger to see if it was a soft or hard deposit, but no material was removed. it was goeey like adhesive. which i assume to be part of my air filter than was chemically disolving on the last ride (&%$#@! you no toil*) as similar deposits were found in the intake tract and carb.
not one bit of carbon. a paper towel and some brake clean had it looking like new in 5 seconds. this head has the head mod(pretty sure RB, cant remember) for pump gas and was polished, which may have something to do with it.
the PV was unexpectedly filthy, but still operated smoothly.
the bid end thrust bearings have gained 0.006" more side clearance since i did this write up.
*no toil- i didnt like the fact that only their cleaner will cut their weird oil to begin with(cant just grab a can of brake cleen and go at it), but i also found out that some combination of what i would assume to be time and arizona garage heat breaks down their oil into something that attacks foam air filters. this is just my hypothesis, as $150 in filters just got ruined when i went to clean them all a few weeks ago. i switched to no toil about a year and a half ago. i have 2-3 filters for each bike and i clean them in batches and rotate them out, so they all got oiled at once and have sat in various states of use for the last year and a half. the 6 years preceding no toil, i have never had an issue, regardless of how long they sat, or how hot they got in the garage.they literally fell apart when they hit the cleaning solution this time around and my bikes all have bugers(like balled up rubber cement type shit from the filter) in the intake tracts. back to maxima hydrocarbon based filter oil for me.