Piston for 1967 60cc sport

[1966smicha]

hello, 

Have a question about which piston I need for a replacement.  My piston has EX with a number 6 on the top.  I measured the diameter to about 50mm with a ruler.  not very accurate.
I see from the parts catalog there are three pistons
1.std
2.  (.25)
3.  (.50)

I know its not the std one.  that one is too small.  any help would be nice.

Thank you

[reed]

1966smicha
Go to a motorcycle shop and get your cylinder and piston measured and if there not one around you send it to me and i will measured
It for  you and tell what size piston you will need.
Thanks.
Steve.

[OldSwartout]

The piston will have the size stamped on the top.  Carefully scrape or scotch-brite the carbon off the top.  You should see either a .025 or .050 stamped on the top. You should be able to determine the size without having to take it anywhere.

[reed]

The reason for having the cylinder measured on the gentleman last post it was low on compression.
So if you get the cylinder measured and the bore check out for any signs of damage it might need
A reborn or not i am aware of the plus sizes on the crown of the piston but i allways check the bore
First, back in the UK most motorcycle shops do re-bores and crank repairs in house in my workshop
I have a boring bar and a honing tank and a bore gauge better to be safe than sorry when it comes
To pistons and cylinders and do it right the first time.
Thanks.
Steve.

[1966smicha]

Hey Steve,

I had taken the piston and head down to my local motorcycle shop.  They informed me that the inside measurement is 42.5 mm  or 1.660 inch.   He said he would try a 42.5 or 43mm piston.   So with that information. 

He also said it looks like it used to be about 42mm x42mm bore and stroke. 
Does that mean I could bet on trying out the .050 piston.  If the standard size started out at 42mm.  Mine is most likely the third choice for pistion range.

Or are there other alternative sizes and similar motorcycle pistons that could also fit. 

Thank you
Shaun

[OldSwartout]

Unless the bore looks scored or otherwise poor, I'd just put in a new piston and rings that are .50 over.  That's the largest BS offered.  If the piston looks decent, you can get by with just new rings.  It would be pretty tough to adapt another brand of piston.  You have to have one that has the right material ( there's a difference in piston aluminum composition for aluminum vs. cast iron cylinders), then the piston pin size,  the ring locator pin position,  the crown height and finally the amount of dome has to match or be compensated for.

For all you tinkerers & mechanics out there - Harbor Freight has their 6" digital calipers on sale for $9.99 with a coupon.  The coupons are in HF ads in nearly all the current automotive and cycle magazines and the Sunday supplements in major newspapers.  If  you don't already have one and you're near a HF store, it's worth the trip.  You can also use the coupon for mail order, I believe, and you can also get up to 7 or 9 at that price. Some of the coupons I've seen are good until November, some expire in August.

[reed]

Shaun
The piston you need is a .50 oversize try Richard for your piston and rings and don't forget the circlips!
Good luck.
Steve.