Ciston to head clearence

[Devins9]

So i just bought a 72mm piston for my blaster to take it to a 240cc, but I dont know how much to bore my cylinder head. Does anyone know how much clearance I need?

 

[stephen12091985]

did you bore ur stock cylinder to 72mm?if so i dont think you should of done that

 

[Wildcard2]

Did you have your cylinder re-sleeved? Or are you getting a big bore cylinder? You can't bore the stock sleeve to 72mm. Pistons are available up to 68.5mm (.100" over bore), but IMO 68mm is the service limit of the stock cylinder before you start running into issues. Your head needs to have a minimum of .045" clearance from the piston to squish band, but on larger bore motors I like to run a little looser than that...about .047" to .050" depending on application ect. Chamber design, squish angle/width will depend on your fuel and porting.

-Brandon

 

[little3mil]

I dont think your quite clear on the whole boring thing man. Boring your cylinder does not raise the cc to 240. If you want a 240cc you will have to get a big bore kit. Do some more research on the search tool.

 

[yb200]

I dont think your quite clear on the whole boring thing man. Boring your cylinder does not raise the cc to 240. If you want a 240cc you will have to get a big bore kit. Do some more research on the search tool.

or contacted a builder.............

 

[Blasterdude27]

Did you have your cylinder re-sleeved? Or are you getting a big bore cylinder? You can't bore the stock sleeve to 72mm. Pistons are available up to 68.5mm (.100" over bore), but IMO 68mm is the service limit of the stock cylinder before you start running into issues. Your head needs to have a minimum of .045" clearance from the piston to squish band, but on larger bore motors I like to run a little looser than that...about .047" to .050" depending on application ect. Chamber design, squish angle/width will depend on your fuel and porting.

-Brandon

Listen to this guy^^^ You can't just get a big bore 72mm piston and bore your stock jug, you need a big bore sleeve pressed in or a actuall big bore kit. As said above do some research...