Mods help gx390

N

Niels V

New member
Hello everyone,
I want go get a honda gx390 (UT2) for my kart but need some clearing up about mods.
Here's what i'm trying to do:
34mm slider carb
Get the head milled and ported
Exhaust
308. cam
Remove governor
Remove oil sensor

The reason why I want to do these mods you May ask is because I haven't had a kart before and would like to keep things simple and powerfull at the same time, all that while having no risk of breaking internals. The track I will mostly go to is low speed so I wont have much use with high revs anyway.

My question is if there is anything I should keep in mind while doing this or am I having a completely wrong image of what I am trying to do? It might sound crazy but I am really not trying to go beond the coil.
 
I would just remove the Gov and oil sensor then put it on the kart and get it running before you do any mods. You might find it's quite powerful in stock form.
 
^^^Agreed. But for like 70 more bucks while doing those mods you can get billet rod. It has good bearings and is stronger. You say you wont turn high rpm so a billet rod isn't needed but you want a .308 cam and with low rpm that isn't needed either.
 
MO Predator Racer said:
^^^Agreed. But for like 70 more bucks while doing those mods you can get billet rod. It has good bearings and is stronger. You say you wont turn high rpm so a billet rod isn't needed but you want a .308 cam and with low rpm that isn't needed either.
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Thank you for your reply!

Sadly I wasnt able to find any billet rods for that money, could you send me a link?
And for the cam, I looked at the stock dyno graph and the gx390 seems to fall off in power just a little in front of 3600rpm or am I wrong about this?
 
Niels V said:
Thank you for your reply!

Sadly I wasnt able to find any billet rods for that money, could you send me a link?
And for the cam, I looked at the stock dyno graph and the gx390 seems to fall off in power just a little in front of 3600rpm or am I wrong about this?
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I am sure on the cam on when it loses power is correct but I am just saying I don't know if you will be in the rpm range much where the .308 makes power. Sorry sir I mostly modify predators and clones. I didn't realize the billet rod was twice the price of a predator billet one.
 
MO Predator Racer said:
I am sure on the cam on when it loses power is correct but I am just saying I don't know if you will be in the rpm range much where the .308 makes power. Sorry sir I mostly modify predators and clones. I didn't realize the billet rod was twice the price of a predator billet one.
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Yeah gx390 mods are atleast 1.5× more expensive and harder to get by, the predator has massive aftermarket support. I live in the Netherlands so predator stuff is out the window. I'm so jealous of u guys, just thrashing on €100 engines all day.
 
By the way does anyone know the size of the breather hose on the gx390 valve cover, I should definetly get a filter for that.
 
Niels V said:
Hello everyone,
I want go get a honda gx390 (UT2) for my kart but need some clearing up about mods.
Here's what i'm trying to do:
34mm slider carb
Get the head milled and ported
Exhaust
308. cam
Remove governor
Remove oil sensor

The reason why I want to do these mods you May ask is because I haven't had a kart before and would like to keep things simple and powerfull at the same time, all that while having no risk of breaking internals. The track I will mostly go to is low speed so I wont have much use with high revs anyway.

My question is if there is anything I should keep in mind while doing this or am I having a completely wrong image of what I am trying to do? It might sound crazy but I am really not trying to go beond the coil.
Click to expand...
Sounds like an ambitious plan for a big block that you will keep in a low rpm range. If you stay with your original build plan then consider an aluminum flywheel, billet con-rod and a high performance clutch set-up.

I agree with Sundog. If you truly want a simple but strong engine then remove the governor, get a performance exhaust pipe and air filter, run the stock carb and enjoy.
You will find the engine is very strong and your tires will be your limiting factor.

Alternatively you can look at the NR Racing website and purchase a 420 Predator Engine fully assembled with the above listed modifications.
 
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