Piston's F**k'd. Big Time, Mate - Whats cheaper? Overbore?
Post Reply    Forum -> Not-So-Modern
Author Message
Joined: 08 May 2018
Posts: 22

Sat Jul 06, 2019 1:12 pm quote
Bought a bike with a p200 engine. Started up fine after I replaced the fuel line and decoked the top end. Needed some fresh cables, so I replaced them and tried to fire it up again, ride it around: no dice.

Compression check showed 65PSI. Oddly enough, this has actually happened a few times over: a bike starts and runs fine when you go to check it out, but you take it off the truck and it wont fire up because the compression was so low in the first place. it boggles my mind.

Anyway, I ordered new rings and went to put them in: bam. Scoring on the cylinder.

I've attached pics of the 'top' of the cylinder, the part you can see with the piston at Bottom Dead Center (BDC): no scoring there. You pull it, and where the piston sits at BDC is where all the scoring is. Nothing that can catch a nail but it has definite grooves.

Looks totally mucked, mate.
What's a cheaper solution: overbore + new oversized piston + oversized rings?
or fresh piston/ring/cylinder combo?

Piston Scoring

bottom half of cylinder.jpg
Bottom Cylinder

top half of cylinder.jpg
Top Of Cylinder

Joined: 26 Oct 2015
Posts: 2618

Sat Jul 06, 2019 1:34 pm quote
Cheaper or best option?...lots of the current aftermarket stock sized cast iron cylinders and pistons kits aren’t near the quality of the original cylinder. It will cost more, but my favorite is an overbore on the stock cylinder, along with the appropriate sized “GS” brand piston.

I’ve had some machine shops charge me $65 for a overbore, and other charge me $35.
73 Rally, 74 Rally, 76 ET3, 80 P200, 06 PX150, 65 Li225 Silver Special, 86,95,96 Elite 80s, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3717
Location: Oceanside/ SF
Sat Jul 06, 2019 1:41 pm quote
Southern California prices $40 for the bore and $80 for the piston. New stock top end

$300 for a new stock cylinder/piston
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3409
Location: Bangkok
Sat Jul 06, 2019 7:10 pm quote
Looking at it I would say a hone and a new piston. I've had worse pistons.

Use a Flex Hone but you need to buy the correct size.

1974VLB 1979VSX 1974V9A
Joined: 12 Sep 2014
Posts: 675

Sun Jul 07, 2019 7:05 am quote
Replace us pretty cheap...

Land of 10,000 Scoots Rally   vespa scooterwest scooter west Motorsport Scooters   AF1 Racing Vespa Austin
Post Reply    Forum -> Not-So-Modern
[ Time: 0.1970s ][ Queries: 27 (0.0365s) ][ Debug on ]