Wow, I haven't updated this since last year, how lazy of me!!!
Probably because the bike has been hard work at the moment, so here I go!!
Pulled the engine out over Christmas and had the crankcases relieved (channeled) so the extra stroke could be accommodated i.e. conrod didn't touch the crankcase on its way passed bottom dead centre. I cleaned up the path through the reed area and opened up all the transfer ports to look more like an 85sx. Had an 85sx base gasket, so used it as a guide and opened it all up somewhere in between 65sx and 85sx. Fitted the 80cc top end kit back on to the +5cc bottom end for a full 85cc!!
Went very hard, bigger change from this than just plonking on the 80cc top end on. Went really good until it overheated and seized, on further inspection I had not engaged the water pump shaft correctly when I installed the clutch cover!! Rookie error and major derp moment!! Piston wash looks good though, a little rich.
So went about rebuilding it, the machinist I've been using gave the hone a go in the barrel and sold me another piston, I gave the water pump a complete rebuild kit while I was at it and painted the clutch and stator covers black with some trick orange anodised cover bolts!!
So loaded up and took it to a Thursday night practice to prepare for raceday the Sunday after, 5 laps in and it flicked a piece of Nikasil and locked and spat me off again!!! Went home Friday night after work to assess the situation, pulled it down to find the damage and was left wondering how I was even going to race Sunday. Sipping on a beer, contemplating life I found a solution. Saturday morning straight down to SupaCheap Auto for some gasket paper to prop the 65sx standard bore up high enough to clear the extra stroke!! Cut out a couple of extra base gaskets and and threw the stock topend back on, calculations are about 69cc!! This should get me through the weekend!!!!
Rolled up raceday and it ran like crap, started throwing jets at it to cure the problem, starting to really dislike Mikuni Carbs!! Anyway, managed to pull off a 4th and two 2nds with a bike that kept bogging every time I executed a bansai move on someone. If I rode it really smooth it was fine, weird?? Anyway walked away with a nice little pocket full of points for the championship and 2nd on the day, great recovery considering where my mind was at the Friday night beforehand.
After pulling the bike apart it turns out the fuel overflow hose off the filler cap was squished under the tank mount...... Rookie error number2!! I was causing a vaccuum in the tank everytime I got rough with it and the fuel sloshed around.
So, ordered another Athena kit (this is starting to get expensive) and rebuilt it again, back to 85cc!!! This time I put the YZ85 carb, a Keihin 28mm, I had bought second hand out of the US on with a trick orange hose kit:
Chucked some new number boards on as well:
Went to Thursday night practice before round 3 of the champs to test, it ran mint all night, in fact the 28mm carb made a massive difference, it was short geared everywhere, so I pulled the 14t front sprocket off and put the 15t on. I was pulling the same gear, same corner harder than before, very impressed!!!!! Carrying longer gearing means the corner speed must've been higher too!!
I'm hoping this is the end of it!!
Plug looked way rich/safe so the Friday some orange mesh I had ordered turned up and I though what the heck do what you were going to do and cut open the airbox!!!
Looking schmick and ready to race!
