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Discussion Starter · #1 ·
Well last winter I got my engine rebuilt..ended up a 673...stage 1 HC, hot rods complete crank...thats about it...
but now..I want more. I wanna punch it out another millimeter and stroke it for the 720. I currently have a slip on but a x6 sparks will be ordered this winter along with the rebuild parts.
Cost isn't a major issue (gotta love the natural gas field pay) but i'm stuck on a few parts.
First..
Hot rods +4 vs. Barkers +4.
I know you need a special piston for the HR..but the HR is cheaper. The barkers cost more..but can use any shelf piston. Is the barkers quality and convenience worth it?

Second
Camshaft. I plan on redoing the valves with Ferreras and new springs, so for a trail bike, will I want a hc2 or hc3? or even x4?

Third
Compression. I dont wanna have to mix race gas, I plan on having a sparks exhaust and aftermarket filter with no lid. what compression should I look at for pistons to stay on pump gas?

Also.. is keeping a stock swinger feasible on a 720 or should I plan on an extended one? and did I miss anything?
 

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The extra mm isn't going to make a noticeable difference if you're already running an 11:1 wiseco. If you go with the Barkers you don't need to bore/hone and replace the piston, you can use what you have in there already. By the time you buy one of the 200 dollar pistons with the offset wristpin for the hotrods crank it will cost as much as the barker +4 would to throw into your existing build.

Don't know what kind of riding you do, but if you're not porting anything right now don't bother with the x4. Stage 3 will be fine.

Again, if you're already running an 11:1 101mm then I'd keep it. I would still keep it to 11:1 even with the bigger cam if you want to stay on pump gas.
 

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Discussion Starter · #3 ·
im thinking its just the 9.9:1 piston..not the 11:1
 

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I should have my Barker crank this week for my build. I am going with 102mm 12:1 piston since I play on the dunes and will be running a 50/50 mix on the gas.
 

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Don't the Barkers cranks bump up the compression on a piston .5 so there fore your 11:1 would be a 11.5 to one. I think you can run that piston just fine with the Barker crank on pump gas.
 

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Discussion Starter · #6 ·
is a stock swingarm gonna be too short for a 720 trail bike?
 

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I ran my 720 on a stock swingarm last year. It was a 11:1 with +4mm stroker crank and Sparks exhaust with no airbox and HC3 with a P&P job. It was ok on that one. Could have been better with a long swingarm but stock did fine.
 

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Ur stock swinger for a trail bike will n just fine I'm sure instead of doing wheelies it will end up just roasting the tires and spinning the whole time which me its still trailable
 
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