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Old 11-20-2009, 07:17 PM   #1 (permalink)
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Hot Rod GX390 Clone

Hello everyone.I need some advice.Iv got a new HF 13HP 390 clone in the box.I want to hop it up a bit but still keep the pull-start if I can?,,so I know there are limits.

20HP would be nice but maybe Im dreaming,,,what parts do I need to buy to make this a Strong fast fun engine?

I would like to stay with high end gas for now,and what would be the best clutch?,,what sort of RPM would this engine turn?,, please give me some of your wisdom on 390s

Im not cheap,and I will try to buy the better parts,,but this is where I need the advice,,,its for a custom mini bike...

Thanks to everyone for your help,Don
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Old 11-20-2009, 08:14 PM   #2 (permalink)
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how much are you looking to spend?

GX390 parts are not cheap.
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Old 11-20-2009, 10:17 PM   #3 (permalink)
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Originally Posted by Strigoi View Post
how much are you looking to spend?

GX390 parts are not cheap.
Thanks for the reply,well I understand that none of this engine stuff is cheap,and money is not a big issue,but I don't want to waste any on junk parts.I can do my own head work,as Iv been porting heads for years,but I need advice on valves,keeper springs and so on.I have a flow bench but it will be a few months untill I get it setup for the small engines.

I know Im going to need a piston and rod,,cam,push rods,carb and so on,,,but remember I want to use the pull start,,,so there are limits,,,,so please advice me.Thanks Don
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Old 11-20-2009, 10:24 PM   #4 (permalink)
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as long as the cam your usin has an easy start on it you could pull start it with 15 to 1 compress
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Old 11-20-2009, 11:24 PM   #5 (permalink)
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if you want to run regular gas, it would be best to stay around 12-12.5:1.

here are a couple of sites that you can start checking out for parts.

NR-Racing.com - check the GX240/270 race parts section
Affordable Go Karts - Home page - AGK - http://www.affordablegokarts.com
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Old 11-20-2009, 11:38 PM   #6 (permalink)
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GX390page heres another i here this dude is a true hot roddr
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Old 11-20-2009, 11:40 PM   #7 (permalink)
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Clements Racing makes good stuff.
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Old 11-20-2009, 11:44 PM   #8 (permalink)
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yea hes got some bad @$$ lookin Stuff there man i realy like the H beams hes got and they arnt that much more than NR stuff r they
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Old 11-23-2009, 10:53 AM   #9 (permalink)
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Getting 20hp from a gx390 clone is pretty easy. The regular off the shelf kits should be able to get you there. Just make sure you read up, and learn how to tune carbs. That's gonna rack your brain for at least a few months.
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Old 11-23-2009, 06:41 PM   #10 (permalink)
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Originally Posted by minidragbike View Post
Getting 20hp from a gx390 clone is pretty easy. The regular off the shelf kits should be able to get you there. Just make sure you read up, and learn how to tune carbs. That's gonna rack your brain for at least a few months.
Thank you,,,,Should I change out the piston also,Like a wiseco?..and what is a safe deck hight?

Who makes the best dragracing clutch with a 1" bore?

Thanks again,Don
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