Planet Minis

mexicanyella · 01-20-2009, 01:50 AM

I've now got a bottom end from a '86 Z50R and I want to get it together for cheap. I don't have any '82-'87 top end parts. I do have a late 70s ATC70 top end. I've been looking at piston/head combinations on the Dr ATV site and saw this:

52MM_PISTON_KIT (NEW_70_DOME) (LONG_ROD) (SHORT_CYLINDER) (10003

Says it works with any type 70 head. Dome looks pretty small, meaning low compression with an old-style head, but being 52mm, instead of 47mm, wouldn't that make some of the compression back up? The TDC volume is larger because of the flatter crown, but the cylinder's volume would be quite a bit more too, and with a 52mm cylinder I don't need to bore the cases, right? That's a $50 cyl. and a $32 piston, plus gaskets, and even with the somewhat low compression wouldn't it still be torquier than a stock 50, for about $90 or so?

arlindsay1992 · 01-20-2009, 07:54 AM

That piston with a 63mm tall 52mm bore cylinder and an ATC head should work just fine. Will be about as powerful as most other 88's. I'd say go for it.

firepower354 · 01-20-2009, 11:12 AM

Compression will be real low. Grab an e22 off eBay for $50 and run it?

01-20-2009, 01:50 AM	#1 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 976	piston selection question I've now got a bottom end from a '86 Z50R and I want to get it together for cheap. I don't have any '82-'87 top end parts. I do have a late 70s ATC70 top end. I've been looking at piston/head combinations on the Dr ATV site and saw this: 52MM_PISTON_KIT (NEW_70_DOME) (LONG_ROD) (SHORT_CYLINDER) (10003 Says it works with any type 70 head. Dome looks pretty small, meaning low compression with an old-style head, but being 52mm, instead of 47mm, wouldn't that make some of the compression back up? The TDC volume is larger because of the flatter crown, but the cylinder's volume would be quite a bit more too, and with a 52mm cylinder I don't need to bore the cases, right? That's a $50 cyl. and a $32 piston, plus gaskets, and even with the somewhat low compression wouldn't it still be torquier than a stock 50, for about $90 or so?

01-20-2009, 07:54 AM	#2 (permalink)
arlindsay1992 "High Speed Record Guy" Join Date: Mar 2006 Location: Northern Virginia Posts: 4,369	Re: piston selection question That piston with a 63mm tall 52mm bore cylinder and an ATC head should work just fine. Will be about as powerful as most other 88's. I'd say go for it.

01-20-2009, 11:12 AM	#3 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 10,989 My Mood:	Re: piston selection question Compression will be real low. Grab an e22 off eBay for $50 and run it? __________________ If it has my name on it I did it;) FirepowerMinis.com Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Pitster/Piranha/Thumpstar bikes, parts, engines and accessories.

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