Different Pistons

waistofhumanspace

New Member
Jan 8, 2011
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michigan
How many different pistons are there for 66/80cc sky hawk engines? I purchaced a cylinder & piston when I put it on my motor the piston hits the head, I see that the connecting rod hole is further down tward the botom of the piston then the one that came originally, causing the piston to travel further up hitting the head. I would like to find the seller that has the correct piston for my engine.:-||
 

Al.Fisherman

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Sep 9, 2009
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Calera, Alabama
How many different pistons are there for 66/80cc sky hawk engines? I purchaced a cylinder & piston when I put it on my motor the piston hits the head, I see that the connecting rod hole is further down tward the botom of the piston then the one that came originally, causing the piston to travel further up hitting the head. I would like to find the seller that has the correct piston for my engine.:-||
I thought there was just one, maybe I'm wrong, maybe they sent you the wrong parts. Did you order the cylinder/piston from the same dealer you bought the engine from?
 

GearNut

Active Member
Aug 19, 2009
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San Diego, Kaliforgnia
There are 3 that I have read about.

1 with a high pin location.
1 with a low pin location.
1 with I don't know the pin location but the pin was smaller in diameter than most.
 

Technocyclist

Motorized Bicycle Senior Technologist
Jul 7, 2008
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Asia
How many different pistons are there for 66/80cc sky hawk engines? I purchaced a cylinder & piston when I put it on my motor the piston hits the head, I see that the connecting rod hole is further down tward the botom of the piston then the one that came originally, causing the piston to travel further up hitting the head. I would like to find the seller that has the correct piston for my engine.:-||
I believe there are 2 types, 1 is with a shorter connecting rod (ZAF50 markings) and a longer piston. The other is with a longer connecting rod (ZAF60 markings) and a shorter piston. I think the one with the shorter connecting rod and longer piston provides better performance and seems to be more durable than the ones with longer connecting rods and shorted pistons.

There is about a 5mm difference between the lengths of ZAF50 and ZAF60. I think the ZAF50 is also used for the 48cc engine but not really sure about this.

You can get a shorter connecting rod, but you would need a machine shop for the 'press in - press out' service. And the machine shop should make sure it is aligned after the 'Press in'.
 
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MotorBicycleRacing

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Jul 28, 2010
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How many different pistons are there for 66/80cc sky hawk engines? I purchaced a cylinder & piston when I put it on my motor the piston hits the head, I see that the connecting rod hole is further down tward the botom of the piston then the one that came originally, causing the piston to travel further up hitting the head. I would like to find the seller that has the correct piston for my engine
Hey, it would help if you said which dealer you bought the piston from?
Piston Bikes carries Grubee Skyhawk kits and parts.
 

GearNut

Active Member
Aug 19, 2009
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San Diego, Kaliforgnia
Why not add additional cyl. base gaskets or a shim plate "stroker Plate" to make up the differance?
Depending on the connecting rod length and wrong piston used, the piston skirt may need to be trimmed to prevent it from hitting the flywheels.
This would be in a short rod, high piston pin situation.
Also in this configuration you would have an extremely low compression ratio as the piston would not come up as high at top dead center of the piston stroke.

tim turbo has the best idea.
 

waistofhumanspace

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Jan 8, 2011
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michigan
can anyone please post links to companys that sell diferent pistons so that I may choose the correct one? or a shim plate "stroker Plate" would be cool too.
 

MotorBicycleRacing

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Jul 28, 2010
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can anyone please post links to companys that sell diferent pistons so that I may choose the correct one? or a shim plate "stroker Plate" would be cool too.
Piston bikes sells Grubee Skyhawk kits and parts.
Piston

and they are one of the only Grubee kit sellers that answer
their phone so call them to make sure the piston is for a
SkyHawk.

The idea of a shim plate is a waistoftime....lol
 

GearNut

Active Member
Aug 19, 2009
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San Diego, Kaliforgnia
Gasbike sells Jet and Grubee engines. I looked at their parts section and unfortunately they do not list which engine manufacturer they are supposed to fit.
Still, I suppose you could call them.
GasBike - Cylinder Parts Cylinder Piston - 80cc

I have not seen one vendor that sells parts for all the different manufacturers of these engines. Typically each vendor only sells parts for the particular manufacturer of engines that they carry. Usually one brand of manufacturer per vendor.
 

oylavabeer

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Jan 9, 2009
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Perth Australia
I recently found this out in reverse ( tried s/h piston in another engine ) and was thinking of this ( what you did )to increase compression and thought it might hit the head but with shims you could maximise it.
 

rustycase

Gutter Rider
May 26, 2011
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Left coast
I like the stroker plate idea of HW !

Only prob there will be port timing.
Fun stuff!

In the end you could really have something, though, once you work your way through it...

Many moons ago I returned a part that did not quite fit right on my suction dredge... another guy working the store that day... he says, "Where'd you get that? That's a part from our R & D and was not supposed to be released for sale to the public." Shucks, it was far better than the standard part I went back to work with......

just sayin...
rc
 

Genisisonyx29

New Member
Jul 8, 2011
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Merced California
okay so i recently did a top end rebuild and i happend to order a longer piston. my engine has the longer connecting rod and shorter piston but the piston i ordered is the long piston. can someone please give me a link to where i can buy my piston from. i bought my kit from this website http://www.bikemotorkit.com/?gclid=CIPG8eGj2rYCFSKCQgodO1AABw they do sell a piston but its 20 bucks! i bought my whole piston rebuild kit for only 13 bucks!
 

Kioshk

Active Member
Oct 21, 2012
1,152
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38
Connecticut
Ahhh, yes; the type-B. You have a SkyHawk, no? I have a used piston if you want it...avoiding those engines from here on out for just this reason: non-ubiquitousnous. I actually like the GT5 a lot, but their proprietary head makes repairs a drag.
 

Kioshk

Active Member
Oct 21, 2012
1,152
7
38
Connecticut
Yeah, same thing. I wish they'd just call these engines The #1, The #4, etc. As far as I know; there are only two 66cc piston types: A (95%) & B (5%), but no one advertise them as such.