My grandson Euan's 
Second "no" go-kart

Sometimes the "way" is to find one in better condition!
My son Dave, Euan's dad, found this one at the local land fill.  Now this is more like it!

This one set him back a whopping $15.00!
The go-kart edumakated amongst you know that it's worth more than that in parts alone.

Read, Set, GO! 
Ah, I think this would be a slow race by any measure

Now you didn't expect us to use a NEW engine now did ya?

Dave picked these two up at yard sales.

Craftsman 2.5 HP $5.00
Red Briggs 3.0 HP  $10.00

In both cases the seller said "it doesn't run, I'm selling it as is" and In both cases, 
all he had to do was , check the oil, drain all the fuel and top it off with fresh go juice!
They both run great, and he has been using them to trim the grass around his sidewalks.

He also has a 10 HP rotto-tiller that he got off the side of the road for FREE that runs great.

Sorry these go-karts are not for sale,
but if you want a free set of plans for a "Yard Kart", then click here. 

Also, check on e-Bay for motors like the ones above.  I have seen them go for around $50.00

Otherwise, start checking your local landfills and scrap yards. You might just get lucky!