Booooring!!!!

[blue 48]

OK so theoreticaly how much of an oversize can these 48cc bores take before somthing stuffs up?. has any one done it? cheers mick

 

[HeadSmess]

from the top.

1, would need to be reported a bit to compensate.
2, would need a new piston (ummm... from a what???)
3, would require re-chroming...

could do a "resleeve" with a cast iron liner, but with whats left i doubt you could get an overbore in there...

 

[motorpsycho]

why bother?
you'll never get a ton of power out of one of these engines no mater what you do.

 

[Deleted member 12676]

I say do it. 48cc is just not enough. I upped to 55cc and love how much of a difference it made. But I cheat with a reed valve. Larger than that is normally necessary.
Look around at the pocket bike shops on-line , and EBay for a piston to match. I have a 43mm diameter KX65 piston in mine.

 

[cloud_2901]

RockSolidEngines actually have a big-bore kit for the 50cc... it's expensive though, really, about $80-odd for the new jug / piston kit from what I remember.

 

[Big Red]

Big Bore Kit?

You don't say what engine you're using. If it's a HT why not just go with the 66/80cc. I always do. A 48cc wont get my fat a$$ off the line. The cops can't tell the difference. It looks almost, Now I did say almost, the same from just looking at it. And if it's not a HT, never mind.
Big Red.

 

[blue 48]

yeah big red it a ht by rock solid 48cc it runs fine already just thinking is all

 

[lazydog]

I've been looking at this kinda, My son races pocket bikes and alot of the parts ARE the same.The problem is gonna be the bottom end keeping together. I'm Experimenting with a 47mm piston and jug now. Runs really fast but it sounds like I'm loosing Crank bearings already, maybe 20 hours riding. There are a lot of 40mm pistons and jugs I'll try next thinking it will be more reliable.

I would be interested in sleeveing the bore, mostly for long term reliability.

 

[Deleted member 12676]

What I dont like about the standard pistons is the thick rings and the excessive ring end spacing. Definitely replace the low end bearings as well as the piston pin bearing. Replace the seals while you are at it.

 

[HeadSmess]

i dont like the surface finishes. i dont like the unhardened parts. i dont like the overweight crankcase. i dont like the eccentric shafts, i dont like the inadequately sized shafts, i dont like the rough cut helical gears. i dont like the rough ports with casting flash, i dont like flathead screws, i dont like changing the chain... i like doing absolutely nothing now except mounting the pipe, a carb, and running them till they die.

cheap engines. youll get them to go hard to a point, then they hit a brick wall.

and every 10% increase in performancce just tends to reduce longevity by at least a third...

i now waste my time on engines that are worth it