The Honda GX390 and the flooded market of Clones (Predator 420, Duromax, etc) are all great engines when they are used for their target application. While some advertise them as 18hp out of the box, the strongest ones will rarely dyno over 14hp.
So what is their "ideal" application?
- Lawn & Garden Equipment (Generators, Lawnmowers, Snowblowers, etc)
- Lightweight toys (Go-Karts, Minibikes, etc)
While they do work in golf carts, there is one major factor that you must be aware of before swapping one into your golf cart.
Splash Lubrication: GX390s and their clones are splash lubricated. Which means that their means of getting oil to the engines critical components involves the connecting rod splashing oil up onto the internal components of the engine. Splash lubricated engines do not have oil filters, which leads to dirty contaminated oil very quickly. This is a very archaic way of lubricating an engine(but its cost effective) and greatly reduces the engines life/reliability. To extend the engines life, the oil must be changed very frequently.
More advanced engines such as ZS 625s and V-Twins (Vanguard, Predator 670, Honda) are Pressurized Lubricated, which means that there is an oil pump physically pumping oil and delivering it through small channels in the engine, to high priority areas such as the connecting rod journal.
Why is this important in a golf cart?
Unlike Go-Karts, Mini Bikes, and Lawnmowers...golf carts are HEAVY. The average golf cart with 2 passengers, a backseat, a top, lights, lift kit and big tires weighs in at over 1300lbs!!! That's 3x the weight of most go-karts.
The higher the weight of the vehicle, the more stress that is put on the engine to move the vehicle (especially up hills). All of that stress ends up at the internal connection between the connecting rod and the crankshaft journal. The only thing keeping the two from having a catastrophic friction meltdown we call "galling", is a very thin layer of oil....
You guessed it, pressurized lubrication does a MUCH better job of keeping oil at the critical point of the connecting rod journal and results in a much more reliable engine when heavily loaded and going up a hill or going off road in general.
Arent there ways to beef up a GX390 or Clone?
YES! You can install a billet connecting rod which can take considerably more stress over an OEM cast rod, it has a built in bearing to absorb shock and facilitate in better lubrication through the use of Babbit material.
While this is a worthwhile upgrade, there is considerable cost and time involved; for a little bit more money, you could just go with a ZS 625cc or Predator V-Twin and be lightyears ahead in the power and reliability department, with none of the headache.
In conclusion, we feel GX390/Clones are a downgrade from your factory engine, unless properly modified. If you are dead set on running a GX390/Clone engine, we can only recommend (from 10 years of experience) it for a golf cart if all of the following apply to you:
- Non-lifted Carts Only
- Factory 18" tires
- No or very little hills
- Light loads (2 persons max)
- Engine MUST have a billet rod installed
- Light Use (once or twice per week)