unknown piston

[2smokin]

i have no clue what the guy before me has done so i pulled just the head off today of my 94 blaster and on the top of the piston i see an arrow pointing to the exhaust side and the numbers 66.92 what is the meaning of this i believe it was bored 1mm and this piston is 66.92 mm to allow for clearance and what not

 

[Blaaster]

Sounds like you got it in 1.

 

[2smokin]

so that is correct it has been bored .40 or 1mm over

 

[2smokin]

and heres another thing i know this piston is tired and the slap im hearing is from this piston the clearance i have is about as thick as a credit card .. and another thing my piston if you try to turn it like you would a lid to something it turns roughly a mm to each side like clockwise or counter clockwise .. no marks or lines or scuffs on the cylinder wall
would this go towards bad wrist pin or big end crank bearings

 

[2smokin]

and yes ive done extensive reading on here about cylinder boring and honing but this is not a race bike nor will it be anytime soon i bought it for 400 dollars running and i dont wanna put that much in the bike right now and i have some bores left also i have just come to find this all out today i know boring and honing is cheap but the closest shop is far away and i dont want 80 dolars in boring and honing after shipping then the top end kit can i just hone it my self with some scotch brite pad and check clearances and install my piston and wat not

 

[OConnor Racing]

Pull the cylinder and measure the bore size. It's possible that the bore is fine but the PO installed the wrong size piston. You're pushing your luck running anything over .005 clearance. Piston slap is the action of the piston skirt hammering back and forth in the cylinder. A piston will only tolerate this for so long before the skit breaks off, becomes wedged between the crank web and the case, then destroys everything from the piston to the cases. The quad doesn't know how much you paid for it or that it's not going to be raced. It's a machine with a serious problem that will not hesitate to self destruct and leave you stranded 12 miles into a ride if you don't fix it. Best bet is to bite the bullet and fix it now while it can still be fixed. A top end, bore, and gaskets can be had for under $200. An engine can run you over $800.

 

[dirtysquared]

Pull the cylinder and measure the bore size. It's possible that the bore is fine but the PO installed the wrong size piston. You're pushing your luck running anything over .005 clearance. Piston slap is the action of the piston skirt hammering back and forth in the cylinder. A piston will only tolerate this for so long before the skit breaks off, becomes wedged between the crank web and the case, then destroys everything from the piston to the cases. The quad doesn't know how much you paid for it or that it's not going to be raced. It's a machine with a serious problem that will not hesitate to self destruct and leave you stranded 12 miles into a ride if you don't fix it. Best bet is to bite the bullet and fix it now while it can still be fixed. A top end, bore, and gaskets can be had for under $200. An engine can run you over $800.

That sums it up the best 2smokin. Its good advise from someone who knows and sees it daily.

 

[2smokin]

Sounds good thanks guys for the help I thing 600 is a big difference

.. But I'm still curious as to why my piston rotates .. Is it supposed to

 

[2smokin]

turns out my rod bearings are ok the piston is a namura 41(marking on inside skirts} wristpin bearings shot and very minimal blow by crosshatching barely visible but there so atleast my rod play is normal .... yayayaaya

 

[2smokin]

hot rods crank c.k 144 on the rod ?

 

[2smokin]

Pull the cylinder and measure the bore size. It's possible that the bore is fine but the PO installed the wrong size piston. You're pushing your luck running anything over .005 clearance. Piston slap is the action of the piston skirt hammering back and forth in the cylinder. A piston will only tolerate this for so long before the skit breaks off, becomes wedged between the crank web and the case, then destroys everything from the piston to the cases. The quad doesn't know how much you paid for it or that it's not going to be raced. It's a machine with a serious problem that will not hesitate to self destruct and leave you stranded 12 miles into a ride if you don't fix it. Best bet is to bite the bullet and fix it now while it can still be fixed. A top end, bore, and gaskets can be had for under $200. An engine can run you over $800.

ok so the piston is a namura 66.92 the ring gap is almost 2-3 mm lol and theres no pegs on the piston to hold the rings and now i found this

a crack in the center port wall sorry for the blurry pic

 

[2smokin]

and the other crack in the same place just at the botton of the wall between ports

what do i do i know i could resleeve but could these be left alone the rings dont seem to catch the cracks and one dont look like a bore will help it

can these be ran safely or is this screwed {i lose} :{... < tears lol

 

[speedyslyder]

well at least you get a new fresh motor to enjoy for a long time to come

 

[2smokin]

well at least you get a new fresh motor to enjoy for a long time to come

so i need a new jug or well a sleeve (crank has no play its a hot rods stock replacement and the piston was namura 66.92 ? yes atleast now i have a reason to do a complete build no riding for me for months now

 

[2smokin]

heres a clearer picture of the bad one

 

[speedyslyder]

you also need to ditch that green basket and get an oem gasket and not put that red silicon on it your choice sleeve or whole cylinder unless that is not silicon and just the way it looks

 

[2smokin]

hmm maybe a reason for a 240 kit or something hmmm maybe go back to stock size less stress on the crank ???
what to do?

 

[speedyslyder]

porting and head mod is way to go but its up to you.i just rode my kor head mod today and it surprised me . it pulled hard. front would not even stay down lol

 

[2smokin]

you also need to ditch that green basket and get an oem gasket and not put that red silicon on it your choice sleeve or whole cylinder unless that is not silicon and just the way it looks

thats how the gasket comes i think this is how i got the bike and is my first time tearing into it i found this today

 

[2smokin]

stock cylinder port job hmm sounds good ? but i got like a 300 dollar budget soo idk