ok, sorry to the OP for theiving his thread, but all of this info is good stuff and helpfull to all.
This is directed towards the post from BIG DAWG 70? Correct????
yes correct. on the OPs link.
i think btb not being smart thats the flash from my camera.
honestly the piston and head was perfect,sorry for the bad pictures
it was spot on...just some carbon build up.
some times people picks up things wrong.
trip,i wasnt insulting cy's,was just my experience with them.
i don't critisise good info btb,thats what this forum is all about,i don't get insulted with other peoples opinions on engines,is that blow by you think? i taught that is harmless carbon build up,if you think it is blow by,what do you think caused it?
ok, looking at your pic, i can see the flash, and as BTB noted, i can see Dark deposits on your piston under the ring. On the exhaust side, you will get some darking of the piston face in direct relationship to the exhaust port. that is normal after some time running as the exhaust gasses are floing into the exhaust port at around 1200*f. some staining is enevidable.
now if you look at the entire circumfrance of the piston, and its dark all the way around (or most of it anyways) that's blowby.
Blow by is caused by a few reasons. Most usually, low case pressure. its high enough to run, and typically well, but as the piston copression the fuel mixture and it ignites, the lack of case pressure cant hold the ring tightly against the cylinder wall, thus allows the still Burning fuel in the cylinder "BLOW BY" the ring, which leaves deposits all around the piston, just under the ring. so blow by is a symptom of Low case pressure and or worn piston ring.
another Large cause for blowby is running around at low speeds, or worse yet as noted, Idleing a tank of gas thru in an attempt to "Break In" a new motor. like you have mentioned its just not needed. and its actually Critical to a Solid performing, long lasting motor to get it started, give it a quick low end tune to keep it running, warm the motor up (1 to 3 minutes of run time) and then take it up to top rpm to make sure the H needle is well tuned (but leave it a tad rich for the first 1/2 tank). once you got the H tuned (about 10 minutes into a run when i first start a new motor) and drive it like you stole it.
by running the new decently tuned motor up to top rpm (10 to 15 second MAX WOT Run time until you have a tank thru it) to build up sufficient case pressure that will adequatly force the ring into the cylinder wall, creating a well seated ring. this will really help the ring seat quickly, and properly, and the result will be a motor that runs just as strong at 5 gallons in as it does at 5 tanks in.
a new ring, and a bit of green scruby time to prep the cyclinder walls will make a big differance in the motors performance. the ring ofcourse will need to be seated, so a good tune and 15 minutes of hitting wot for 10 seconds and down to 1/2 throtle, then back to wot will help ensure a good seating of the ring.
just to FYI, your 29cc had good torque becuz of the 2mm stroker crank, not the cylinder (unless your comparing it to the 32mm 23cc motor). the zen has better mid top end from the stock 28mm stroke crank.
Dawg. look at your motor, more specifically just under the cylinder. older smartechs had CYs in them. im not sure when they went with their own 3 bolt motor, but im suspecting your motor is the cy 23. if you look at the case/cylinder on the side of the motor, if its CY you ll see numbers like 28-32 (28 signifiying a 28mm crank and 32 signifying the bore size) or similar. its possible you cant do anything with your current motor, but if its a cy, there is much you can do to rebuild it, AND make it a strong running long lasting motor (new crank bearings, seals, and a Zenoah topend kit.
im not trying to argue with anyone, just giveing first hand experience, as well as knowledge gained from working with ESP.
