Chainsaw Repair

It would be interesting if you could dyno it step by step also but that wouldn't be easy unless you live by Madsens or Chad in PA.

It would be interesting if you could dyno it step by step also but that wouldn't be easy unless you live by Madsens or Chad in PA.

agree.  this 066 is just numbers.  when the goal numbers cannot be achieved as in this 066 jug..... there is no way of to verify the outcome of how much actually was gained.

the bmep curve follows the torque curve in the dyno graph.  knowing the factual baseline stock kW and Nm from dyno testing, makes the calculations accurate.  the program is just a tool to help narrow things down.

regards
-joe

can't get back in to edit my first post to put these latest text files together, and get rid of the others.

one for stock. 02/03/14

one for big bore. 02/03/14

regards
-joe

You won't be able to decrease the exhaust timing that much.  With the stroke and rod length of this saw every 0.010" is about 1.5 deg of duration on the exhaust timing.  So to go from 175-160 you need to remove around 0.1" from the squish band and the bottom of the jug.  This would then raise your intake timing by around 14 deg duration which would be way too high.  Also the exhaust port would probably be free porting because they are already very close to doing so stock.

You won't be able to decrease the exhaust timing that much.  With the stroke and rod length of this saw every 0.010" is about 1.5 deg of duration on the exhaust timing.  So to go from 175-160 you need to remove around 0.1" from the squish band and the bottom of the jug.  This would then raise your intake timing by around 14 deg duration which would be way too high.  Also the exhaust port would probably be free porting because they are already very close to doing so stock.

took 2 mm = .078 inch off th squish band, and similar 2 mm off the base for a couple of reasons:

stock oem cylinder cylinder length TDC to BDC was 80.82 mm (including squish clearance).  the skirt length of piston was 20.06.  at BDC....80.82 - 0.5 squish - 40 stroke - 43 total piston length = -2.68

the knockoff, is way out, imo, as far as time-areas are concerned.  did not pay to much attention to it after i saw the base numbers.  the cylinder length was 80.64 mm on it.  further time spent typing numbers into the program i will not do.

the way i see it, on the oem jug, the piston skirt extends 2.68 mm below BDC.  am i thinking about this wrong?

think i have the room.  the intake time-area is way too long and large.  the intake floor will have be brought up to anyway to balance the ports.

the other reason is for ease of math, adding or subtracting 2.

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there is no way to get these ports to the ideal STA number goal.  as i mentioned before, the program is just a tool.  imo, balancing the ports is the most important idea.  the port sizes and timings in the stock jug will be
balanced to approximately, to a value of 1.5 times larger than the ideal STA accross the board.  ie. exh sta 1.5x ideal, trans 1.5x ideal, etc.  only choice i see.  cannot be made any smaller, and the height  between the exh. an trans prevents this.

to get them to ideal, would require welding/replating or a sleeve pressed in.  not a fight that i want to get into.
things would be much easier on a better original casting.

regards
-joe