New belt driven pump for Honda gx390?


I think those pumps can fit on engines with more HP than a GX390, so it might be capable of 4000 PSI on another engine, but with a GX390 it will top out around 2500. Something like that.

Gear drive is better than direct drive. Direct drive, the crankshaft goes straight into the pump to turn it at the same speed… gear drive the crankshaft turns gears, which then work the pump at a different speed than the crankshaft is turning. Something like that. I think it’s better for the pump to be gear driven, and it pulls water from a buffer tank better. …something like that.


Awesome thank you so I can run a buffer tank on just gravity like a belt drivin correct?


Sorry man kinda a noob I only thought there was direct drive and belt driven


Direct drive is the only type that requires gravity feed, although i think ive seen some people here and there say that they pulled water without gravity assistance.

Gear and belt driven will pull water without needing gravity assistance.

Meaning: If you have a gear or belt driven, you dont need to have the tank higher than the engine to pull water.


Am I correct in my thinking though that if a gear reduced pumps still rotates faster than a belt driven pump? Is one more efficient at pulling water than the other?

I thought I read that the slower the pump turns the better suited for pulling water.


That’s makes sense from a suction standpoint.


I think i recall seeing a lot of people stating that belt driven rotates slower than gear drive… however, i wanted to make sure about what i was saying before i repeated that here, so I did a little searching. Here’s a thread where several people discuss this issue. Skimmed through it, but if i am interpreting it right, Jerry and Russ (Two guys that know what they are talking about) say that belt and gear turn at the same RPM. There was one guy that disagreed… but it seems he might have been wrong, based on the conversation.

So it might be true that a slower turning pump pulls water better, but according to Russ and Jerry, belt driven and gear driven turn at (or near) the same RPM… so they will perform equally.


Jerry McMillen’s posts on that thread were spot on.

My summary/takeaway:

Gear boxes are typically 2.1:1 reduction. So they require a different spec’d pump (1,750 rpm) than a typical belt drive (1,450 rpm). You could use a standard belt drive pump on a gear box, if you reduced the engine rpm. But that’s just silly. And likewise, if you had a gear reduction pump sitting around, you could find the right pulleys to install it as a belt drive.

1,750 rpm is still way better than the 3,600 rpm a direct drive turns, and it will have no problem pulling from a tank.


Hey so I was about to make an order. Your saying the one Alex Lacy linked is better than the one you linked? If so how come? Cause from the look of it it looks like the one you linked is a better pump/deal


Alex linked an udor. Much better pump


Thank you


It’s not so much the slower rpm that allows them to pull better it’s the greater vacuum caused from the longer length of piston stroke in the slower spinning pumps