Buying the right cylinder

[TheBaldKiwi]

Anyone know what to look for when it comes to buying replacement cylinders? I want to start experimenting with porting, and since cylinders are so cheap id like to buy some to work on. I'm not sure what dimensions I need to look for to match my engine. I have a 40mm stroke pk80 type engine with a type A piston.

 

[6blueoval9]

The Zeda cylinders run $25 a piece....for what you want to start off with the cylinder you have shouldn't be at much risk to clean up the ports...I would start with that first.

 

[TheBaldKiwi]

The Zeda cylinders run $25 a piece....for what you want to start off with the cylinder you have shouldn't be at much risk to clean up the ports...I would start with that first.

Aren't the Zeda engines the hybrid type with a slightly shorter stroke than 40mm? If so, wouldn't the cylinder be shorter to compensate? I have already done Port correcting on the cylinder I currently have on my engine, I just want to experiment with port timing.

 

[FurryOnTheInside]

IMHO,
Buy a piston instead. Experiment with notching the skirt on the intake side, and ramping the top at the exhaust, by half a millimetre,, then try that out, then start trying half a millimetre at a time raising the exhaust port (1mm is common)
When you have found where "just right" was and "too much" is you can put the original piston back in to go back half a millimetre and have the correct modding to your original cylinder.

 

[6blueoval9]

Aren't the Zeda engines the hybrid type with a slightly shorter stroke than 40mm? If so, wouldn't the cylinder be shorter to compensate? I have already done Port correcting on the cylinder I currently have on my engine, I just want to experiment with port timing.

Like furry was saying it's cheaper to experiment using the piston as a timing experiment...pistons are only $10 a piece.

To do as I was saying with just cleaning up the ports, no timing changes will need to be done.

You might be right on that hybrid thing....I'm seeing a 39.5mm crank kit now offered on Zeda motorsports sight...I was thinking the Zeda 80 was 40mm...I'll find out for sure and get back with you on the stroke.

 

[FurryOnTheInside]

More like $5 on eBay, with rings, for the low pin type pistons, straight from China.

 

[gary55]

Anyone know what to look for when it comes to buying replacement cylinders? I want to start experimenting with porting, and since cylinders are so cheap id like to buy some to work on. I'm not sure what dimensions I need to look for to match my engine. I have a 40mm stroke pk80 type engine with a type A piston.

I know you said it's a type A piston but some sites are labeling them backwards. So just to clear it up you mean it has the low wrist pin hole? the one on the left is the A type.
What are the markings on the rod.
The Zeda engines are a 40mm stroke, 89mm rod, B type piston.View media item 60316

 

[TheBaldKiwi]

I know you said it's a type A piston but some sites are labeling them backwards. So just to clear it up you mean it has the low wrist pin hole? the one on the left is the A type.
What are the markings on the rod.
The Zeda engines are a 40mm stroke, 89mm rod, B type piston.View media item 60316

When I refer to a type A piston its the low wrist pin design.

 

[gary55]

Anyone know what to look for when it comes to buying replacement cylinders? I want to start experimenting with porting, and since cylinders are so cheap id like to buy some to work on. I'm not sure what dimensions I need to look for to match my engine. I have a 40mm stroke pk80 type engine with a type A piston.

https://www.ebay.com/itm/Cylinder-B...232589?hash=item4b0fe54bcd:g:EWwAAOSwRXRZPF0K

 

[Tyler6357]

I thought "pk80" refers to the ones with the lower wrist pin location and shorter connection rod that are 40 stroke. The "GT" refers to the ones with the higher wrist pin location and longer connection rod, these were originally 38 stroke but now they are making them 40 stroke.