66,50 piston ... 90psi compression

[GermanDude]

Okay folks,

My engine has a 66,50 piston and a compression of ca. 90psi now i wanna rebuild the rings!! but i couldn´t figure out what kind of rings i need?? or did i need to bore it to the next size?? did i need to bore to 67mm and get a new piston with rings?

i tried the search but coudn´t find the answer......

Ihno

 

[lowkhalbalr]

who makes the piston?

 

[acezeesawtooth]

well tear it apart and look at the walls if they arent damaged then the rings just wore out... it may be a good idea to get the next size piston and bore it anyways to be safe... also not calling you dumb just want you to be certain how many times did you kick it over for that reading?

 

[slickerthanyou]

If your cylinder is good and the piston looks good no sratches, scrapes I'd say re-ring. If any scuff marks I'd go to next size.

Check the rod bearings too!

 

[scotj77]

yeah could you explain how you did your compression test just to make sure you did it right.

 

[GermanDude]

okay
here is everything what stands on the piston

6545H

573MO6650

i kicked it so long until the needle from the compression tester stoppes (with full throttle)

 

[scotj77]

did you have the throttle open while kicking it?

 

[acezeesawtooth]

ok id say go ahead and take the cylinder off and check the cylinder walls make sure there are no marks anywhere then look at the piston make sure there are no marks on it... and order a new set of rings... be sure to watch the how to install a cylinder video in the DIY section and good luck dude

 

[slickerthanyou]

okay
here is everything what stands on the piston

6545H

573MO6650

i kicked it so long until the needle from the compression tester stoppes (with full throttle)

Correct way! !

 

[GermanDude]

yes i had the throttle open

 

[acezeesawtooth]

since you already have the head off just take the cylinder off and look... and for heavens sakes get new gaskets too dont reuse the old ones... and watch the video of how to make a leakdown tester (figured this would be easier than you buying one since ur in germany) and make sure u done have any airleaks when its all back together

 

[acezeesawtooth]

as long as it doesnt have any scratches or nicks in the cylinder then yes just rings

 

[GermanDude]

so just new rings in 66.50?? should i let it hone??

i just orderd a leak down tester from holeshotman!!

 

[scotj77]

yes you need to hone it but you also need to make sure you are not out of tollerance on the piston to wall clearance. honing it gives it the crosshatch pattern which helps the rings wear to the exact shape of the cylinder wall

 

[acezeesawtooth]

ok sweet i didnt know if he would ship it that far... but yeah you will definitely need it

 

[acezeesawtooth]

yes you need to hone it but you also need to make sure you are not out of tollerance on the piston to wall clearance. honing it gives it the crosshatch pattern which helps the rings wear to the exact shape of the cylinder wall

yeah i wasnt sure on the hone good call man I:I

 

[brandoz28]

yes you need to hone it but you also need to make sure you are not out of tollerance on the piston to wall clearance. honing it gives it the crosshatch pattern which helps the rings wear to the exact shape of the cylinder wall

not to mention takes material, and you also have to make sure its not out of round

 

[sicivicdude]

That's a wiseco part number you put out there. Wiseco sells rings directly or through their vendors.

If you have an spring inside caliper and dial caliper you can determine if the cylinder or worn over size or out of round. Both of those can be had at harbor freight for less than $40 and you can do your own bore sizing from then on.

 

[GermanDude]

ok sweet i didnt know if he would ship it that far... but yeah you will definitely need it

i live in the US for 4 years

...so i have to take the cylinder apart bring it with the piston to the machine shop, let it messure out and then hone or bore it depends on how it looks after that new rings or a new piston with the right size, right???

 

[scotj77]

yes you take the piston w the cylinder to a machinist and he can measure it and tell you if you need a new piston. hopefully he is honest. if you don't need a piston he should hone it as little as possible then order new weisco rings.