Udor pump series question

I’m just getting started in pressure washing and want to thank everyone that contributes here for the free education.

I’m looking at buying a used trailer with a Honda GX390 and Udor Rubiera 4/30 pump.

The way the trailer is set up he has the direct drive pump plumbed into the bottom of a 300 gal tank. I have enough experience with pumps and have read enough on this forum to be leery of this type of setup.

My question is about replacing the direct drive with gear driven. I’ve done my research and know it can be done but shopping around I can’t tell what’s what.

It’s calling this “solid shaft series”. They also have direct drive, gear reduction, etc.

Is solid shaft a belt driven pump? Or still in the direct drive category?

May have just answered my own question. Looks like solid shaft might be for electric set up. Can anyone confirm?

Any new pump made for belt can be used for gear…
but you have an udor direct drive?

Unless your upgrading to more gpm… keep what you have, contrary to belief it will feed from your tank just fine.


Thanks for the info. I was planning on running it until it quits. Just looking ahead.

It is direct drive from what the seller told me. This is the best picture of it.

You have a direct drive, You CANT convert that pump to a gear drive, the shaft inside is diffrent… Like a Cam on a car.

You would need to start over like I did, buy the gear drive and the gear drive friendly Udor pump.

I need to get to the bottom of this ‘direct drive draw’ issue. People keep going back and forth about whether a 4/4k will safely draw from a water tank. When I get healed up I need to test mine, sure would be nice so I don’t have to hook up my 120v pump.


Your direct drive only takes in what is being delivered…it won’t suck in any water. A buffer tank should feed your direct drive pump enough flow no problem.


They 100% work with a buffer tank. Never had a single issue with it yet. (GX390 4@4 direct drive).


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So if my 65 gallon horizontal tank puts out say, 5gpm, my pump won’t cavitate even though it doesn’t have the ~50psi from a spigot?

Well that depends on how full it is, and what size plumbing your using

If you have your tank at 60 gallons constantly and running a 1inch bulkhead and hose you’ll be fine.

And if the hose is a straight run 3-4 ft.

I also wouldn’t run a filter…

Nice, good to know. I’ll definitely try it!

In my land, that’s 265 litres! Wow.

That’s about 20mins @ 4GPM with no water feeding it at all. (You also top up in bypass of course)

The mains pressure is not relevant as such. So long as the water is “introduced” to the pump inlet constantly, the pump will do the rest.

I have a 10 gallon tank and it’s never emptied yet. That’s surface cleaning and house washing.

If I had your tank…wow, definitely no probs for me!

Thanks for all the replies, I think I’ll run the pump till it quits and be saving up to upgrade to an 8GPM someday.

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So you’re saying that you can’t take the direct drive pump off the gx390 and bolt on the gear drive?

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No, he’s not talking about the engine. He said you can’t convert the pump to a gear drive. You can bolt anything you want on the engine whether it’s a direct drive pump, gear driven pump, hydraulic pump for a wood splitter, etc.

I should say you can bolt on anything that uses the same shaft size.


It’s the speed of the pump that’s relevant.

Sorry if you already know this, but for clarity…

A direct drive pump runs at the same speed at the engine.

The gearbox driven pump will run at half the speed a direct drive pump. (The engine stays the same RPM in both cases)

Here’s the thing - a pump designed for a gearbox (or belt) won’t work with a direct drive and the direct drive you have, won’t work via a gearbox. (It will run too slow).


Yeah that’s what I figured. I just got confused by his wording.