Just wondering what is the gain from going from 125 to 131, other than other changes. Is it worth it at all? JMO
Having built quite a few opens based on the leopard, I found it's sub pare to other options.. the starter will not start a alky open leopard., the crank halfs are marginal, as the stock ignition is not a total loss system and will need the powerpack., it also has a 2port exhaust (in the tag class, it's allowed a lower weight due to its lack of power) than more current 3port tag engines..
With that being said, before the soniks came out and were economical, I built all of mine on a iame lowerend (stud relocation required) using a sonik or, tt25 crank, I've also built them on a prd, and sonik lowerend, (stud relocation required)., however if your going to use sonik stuff, why even use a leopard? We have soniks out to 131,140, and 148cc's.. the case's of the soniks due not have wet jackets in the case, the center of case's have to be relieved for the rod, and a reed spacer is required, I use a old reed cage and machine off the reed part, just leaving the flat part, the spigot hole also has to be enlarged on a iame case..
It's been awhile, but if I remember right, the leopard has a 100mm rod, and with the extra stroke the piston will shank out on the crank at bdc, so the skirts will have to be trimmed, (being cautious not to free port the engine..) you also have to trim spigot hole ledges or piston will shank out on them.. you will also need a spacer plate for bottom of cylinder., building a hybrid open is seldom just a bolt together project, count on machine work., measure and plan it out..
And I disagree about stroking being better than a bigbore, and it is a easier than building a stroker, I have crank works here in Phoenix do all my cranks, I can't do it for what they charge,.
Alot of the tag class tracks have a leopard only class so they still hold some value alot of times more expensive than a Sonik or prd, vortex, which are better engines., I can pick them up for 4-600.00, if you can do the work yourself, you can build a 131 or bigger open for less than 1000.00 or so. (not counting, carbs, pipe, etc.)
With the leopard, to get the power, be prepared to do some major porting due to the 2 port exhaust, it's limited in the stock configuration., Abetter option would be just start with a more current 3 port engine and get more power stock., basically a open leopard is going to be a money pit..
One thing I will add, i've built a quite a few prd opens, the rods (much like a kt rod), I was a little worried, but i've had no failures with the rod.. they are cheaper than a iame rod and stand up to the the open mods..
The soniks, prd's, vortex's run a selletra or pvl, or the prd use's its own ignition, they are total loss systems, current kart type ignitions..