By far one of the best values is the new
Stage6 Big Racing 77cc kits. They have been nearly impossible to get, but Maxi is saying available in 12 weeks. If you can wait this would probably be the best kit for what you are talking about doing with your bike. If you get this one then get the 24mm PWK carb, and ether the MetraKit or the Vocal pipe.
The
Top Performances Rose 70cc cast iron kit is a decent kit. This is probably the lowest level I would get for the bike. This one has the modular head, which cools better. But this kit is cast iron, and I'm not really a big fan of cast iron because it's heavy. Still Top makes nice product, and if you got it you would probably be pretty happy with it. If you go with this one get the 21mm CP carb. Any of the above listed pipes will be fine.
The
Metrakit Pro Race 3 70cc is one of the best kits available in this class. It has a modular head, and is a proven top end. If you get this one then make sure you get the MetraKit pipe. The other pipes wont work with this top end, although you might be able to get adaptors for them. Also go with the 24mm PWK carb.
The
Top Performances TPR 80cc aluminum kit is a nice step up from the Rose. It's has a larger barrel, modular head, and it is aluminum. Ed has one of these on his bike.
The
Polini Alu Race 79cc kit probably wouldn't be my choice, but it is a nice kit. It does have two rings, so if I had it I would probably only run the top one. It is an aluminum kit so it will cool nicely. This kit would work well with the 21mm CP carb, and any of the pipes listed above.
The
2Fast 70cc kit is by far the most expensive. They have been blowing people away with their technology. This is probably the most powerful kit you can put on the stock stroke. I would seriously consider putting in a better crank, and bearings with this kit. That's not a bad idea to do with any of these kits, but you really want to do it with this one. To get the best performance out of it you'll have to case match too. It's nice to do with any kit, but in this case it's even more important.
2Fast also makes a 100cc kit, but that's going to require lots and lots of upgrades for your bike to support. This kit would require one of the better pipes—ether the Metra or Voca, and the 24mm PWK carb.
Bidalot makes a lot of nice stuff for this engine including some of the larger sizes, however their
Replica 70cc is both quite nice, affordable, and accommodates the stock stroke length. This kit would work well with the 21mm CP, and any of the pipes listed above.
