this top end got skills !

[skyash]

I just took off a cylinder from a pocket bike and here's in side. Y is there a slit above the exthorst port? And y are there no walls on the transfer port's? One more. What are the 2 slits up to where the carby should be? Can eny of this be done to a 66cc cylinder?

 

[skyash]

Here's the piston with windows the piston conrod and crank can fit in your pocket lol

 

[HeadSmess]

the transfers dont really need walls, plus it makes manufacturing really easy.

the two slits are boost ports to direct gas flow to the top of cylinder as exhaust flows out the port.

the exhaust bit...who knows? lower cylinder pressure a bit quicker before the transfers open, so you can get a decent blowdown time despite the timing between transfers and exhaust being a minimum? your guess is as good as anyones

this the one you got on ebay? the proper racer? reeds feed direct into crankcase, the way they should do? leaves a lot of cylinder wall just asking for holes to be added

so no, you cant quite do all of this to a HT/china girl which are always going to be a compromise with reeds stuck on the side of the cylinder.

 

[skyash]

But what if I put slits up to the carby port bottom or next to the port ether side? I did one straight down from the intake port a long time ago and it seems to have better get up and go on a China girl

 

[skyash]

Here's the head it comes in like 4 parts bit of a pain

 

[HeadSmess]

go find gordon jennings "2 stroke tuning" book, online... then read it.

problem with hacking holes willy nilly into a cylinder is understanding gas flow. where the ring ends are located. etc etc. takes some experience, and can you make two that arent just similar...but IDENTICAL? so you need to be able to repeat certain mods, whilst knowing which bit NOT to repeat.

cylinders are "relatively" cheap... noone is stopping you!

 

[skyash]

One more off topic now I pulled it apart I got no gaskets I just had silicone can I use Teflon tape to put the cylinder back on i think you said roll some in to a thin rope and put it around like a gasket?

 

[Deleted member 12676]

konix, did you see my pages in Spanish?
Where did you buy the 40mm bore cylinder? Does it fit the 48cc cases or the 69cc cases?

another problem with modding these engines for high RPM is the extreme stresses on the crank bearings due to incorrect counter balance at the crank wheels. The forces increase exponentially with RPM. Of course that problem is readily corrected by drilling a couple of holes in the crank wheels.

 

[Deleted member 12676]

I removed the transfer ports walls from one of my cylinders and it ran worse.
Why? Then the air being pushed down by the piston interacts with the air going up the transfers in a negative way, creating resistance and unwanted turbulence.

 

[HeadSmess]

One more off topic now I pulled it apart I got no gaskets I just had silicone can I use Teflon tape to put the cylinder back on i think you said roll some in to a thin rope and put it around like a gasket?

if you can replace the base gasket with teflon tape...kudos. you are doing well. use cardboard. side of a cereal box. place it on crank case and tap gently with rubber hammer, then simply trim to the line. or use ink to mark it.

teflon is only good for the head gasket.