gx390 open build

kartkevin39

kartkevin39

Member
Just got a new GX390 from work for free. Was wondering how much it may cost to make it an open engine and/or who builds them, races them, and the success they have had with them? Thanks in advance.
 
a true open motor.........2600+, you will need forged pistons, rod, flywheel, complete valve train, roller rockers and crank if turning over 7500rpm, head work will be about $500 alone.................I think 1500 will not even buy the bottom end........want to be really fast 3500 with a 390, and it will be tossed for the 460 from Vegas........don't get me wrong I love the 390 with a mild build, cam, compression boost is torque city, but true open motor are expensive......but the power is awesome, really not worth the price but it is awesome.
 
Or go belt drive and only cry once. Or twice if you get the wrong size belt...Maybe a 3rd time when you change ratios...4th time when a rock chews it up....5th time when it gets oiled by the motor.....
 
I have friends that have a couple of built gx390's with less than 1500 in them and they are a very competitive engine on the small tracks in open/rwyb classes
 
A lot of truth in all of the above posts. It all depends on how big and nasty you want it built. Sure, you can build one for under $1500, or you can put >$1500 in parts alone into one. We still build a few of them each year and the "standard" build, if there is one, is around $2800 (including a new genuine Honda engine.) If you want a billet head, it's even more.

Many years ago we were building a lot of stroked animal engines for around $2500, then along came the big block and you got about 10 more CHP for the same money, so the trend was to build 390s for a while...Now that the MX450 and other big bike motors are the hot ticket, 390 builds/sales seem to have been dropping over the last couple of years. It's all about bang for your buck I suppose. I understand the appeal of pulling a stock engine off a wrecked bike and running it, but unfortunately that's not enough anymore as those engines are being built up now as well. (Hint: JGR and the likes don't work for what kart engine builders typically do.) :)
No, you'll never make a 390 industrial engine compete with a bike motor, but on a small track they can still hang.


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Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
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