cylinder measurments not turning out please help

[chetgoff]

ok so i took some measurements. I measured the amount the head was milled and i'm getting 2mm also TOP of exhaust port to deck is 28.5 mm

also when i measure with piston all the way down to deck i'm getting 2.07 on 1 side and 2..08. the pistons say 513 on top with some writing inbetween and then6450 so i'm assuming it is 64.5 mm piston.. I need to take more measurment for the porting i'm sure just wanted to put head back on and do a compression test. can you tell me where i should be on compression and also why would my rod not be even measuring to stock?

[sleeper06]

Are you asking a question or telling something?

[shakar]

ok so i took some measurements. I measured the amount the head was milled and i'm getting 2mm also TOP of exhaust port to deck is 28.5 mm

also when i measure with piston all the way down to deck i'm getting 2.07 on 1 side and 2..08. the pistons say 513 on top with some writing inbetween and then6450 so i'm assuming it is 64.5 mm piston.. I need to take more measurment for the porting i'm sure just wanted to put head back on and do a compression test. can you tell me where i should be on compression and also why would my rod not be even measuring to stock?

i pretty new to this but i think the 513 pistons are blaster pistons ran when using a 4 mill crank .thats prob way your rod # are off.also i think depending how much is shaved off your head will dictate what your comp is .a stock head with stock crank shoud be around 120 comp

Edited February 6, 2010 by shakar

[chetgoff]

thanks for they replies and yes i'm asking to try and figure out what my motor is. picked this bike up on a good deal but guy did not know anything about motor. so i'm just trying to figure it out. thanks for the help?

[methyman]

513 is a Wiseco Banshee piston, 573 is a Blaster piston which start at 66mm. If your 4mm is short rod crank it would use 513 pistons. If it is a long rod it would use 795 pistons.

[chetgoff]

when i'm measuring the stroke length im putting piston all the way down and measuring to the deck. is this thr proper way?

[Hilarious]

when i'm measuring the stroke length im putting piston all the way down and measuring to the deck. is this thr proper way?

 

that is how i measured mine.

2.07 in converts to 52.578 mm.

are you measuring on the very outside edge of the piston crown to the top deck?

are you using a good set of calipers to measure?

are you sure the piston is at the very bottom of the stroke?

just making sure.

[chetgoff]

thanks for the response this thing is driving me crazy. yeah i'm measuring the outside edge of the piston to the deck. i'm using a 6 inch ruler that has a sliding thing to mark where it's at. then i use my calipers to measure it. i did it several times. and got the same numbers. not sure why. I will try again today after work. and see what i get.

[bansheesandrider]

when i'm measuring the stroke length im putting piston all the way down and measuring to the deck. is this thr proper way?

You need to measure from the deck to the piston at TDC and then measure again at BDC and the subtrtact the TDC from the BDC. If at TDC, the piston sticks out of the cylinder, as a stroker will do, you need to ADD that measurment to the BDC. Also, try measuring in millimeters so you don't have to convert it.

[chetgoff]

ok so I checked again. The side of the piston when at TDC the side is almost flush with the deck but the center of the piston is sticking out of cylinder. not sure if that's what our talking about when you said it will stick out. I used a piece of wire to measure when pistons are at bottom. on one cylinder i'm getting 5.58 and the other is 5.51.

[bansheesandrider]

ok so I checked again. The side of the piston when at TDC the side is almost flush with the deck but the center of the piston is sticking out of cylinder. not sure if that's what our talking about when you said it will stick out. I used a piece of wire to measure when pistons are at bottom. on one cylinder i'm getting 5.58 and the other is 5.51.

I meant if it sticks out at the side, the center of the piston always sticks out on a Banshee. 5.58 and 5.51 what? centimeters? It should be in millimeters and it should be 54 mm if it is stock, a 4 mil will have a 58 mm stroke. Both sides should measure the same after subtracting the TDC measurement from the BDC measurement. Since you are getting two different measurements, it is sounding like you have a poorly made crank that has different strokes for each cylinder, and it may not even have a full 54mm stroke if that is the case. You should be using a depth gauge or a caliper with a depth measurer on it for the best accuracy, not a piece of wire and then measure the wire, that is a VERY inaccurate way of doing it. If it is a 4 mil stroker AND there is no spacer plate between the cases and the cylinder, then the edge of the piston should stick out of the cyl. 2mm if you have stock lenght rods, or 7mm if you have long rods and 513 series pistons. The 795 pistons are shorter to make up for the long rod, and then you would be back to it sticking out 2 mm with long rods and 795 pistons, this is at the edge of the pistons.