what is the diameter of the piston?

[kyle]

what is the diameter of the piston in a 1985 250 es big red it is all stock. it dropped a valve and now i need a new piston . i am either going to buy a stock diameter piston if the cylinder isnt worn that bad but if it is i am going to buy a oversize piston so i need to know the cylinder diameter and the piston diameter
thanks
kyle

[YamaChuck]

Kyle, according to my book it's a 74 mm bore. You might want to confirm this with a few people.

[Fuzzy]

Yep the bore is 74 mm the stroke is 57.3 mm.

I am going to move this over to the tech section.

[kyle]

yall i got 73.88 mm on the piston on my dial caliper and so did my grandpa.
is it inside the wear limits? if so i am going to just buy a stock piston and rings.

p.s. can a stretched timing chain cause the valves to open at the wrong time. and does anybody know the stock legth of a timing chain.

p.s.s.
i called honda yesterday and asked them for the stock piston diameter and they said they couldnt find it! i know the guy personnaly cause my dad grew up with him. so i know he isnt lazy.but anyways he priced all the parts i need and it came up to like350 .i was like .......well.......there goes this months job money
that sucks.

kyle

[kyle]

i ruined the piston that is why i need a new one. even if it is not worn at all it is shot.
kyle

[Fuzzy]

The reason that your piston measures 73.88mm is to allow room for the rings. The rings are actually 74mm.

And yes a streched chain will throw your timing off.


I wouldnt buy them from Honda. You can get a piston kit from dennis kirk with rings for around $84.00. And a top end gasket kit for it is around $20.00.

[250sx]

check out www.recreationunlimited.com for the best prices on engine parts. what you can't get there get through servicehonda.com (call them, don't email)

[dads]

just right click, and save pic ashttp://adam.cheshire.net/~dads/pic/specs.jpg

[kyle]

my dad is ..well ..like computer eliterate so he wont let me order anything of the computer.so i have to order from honda or dennis kirk ,i got a dk catalogue.if i am reading dads post right my piston is just under the worn limit so i am going to replace it with a stock one and i am getting a new cam chain.
thanks
for all the help
kyle

[250sx]

I hope he's paying for it b/c it is gonna cost twice as much. You can always call them over the phone, that's what I did. I've ordered from both places without any problems.