# Pulley size

I have a ts2021 g series it’s rated at 5.5 GPM but in my test I got only 4.5 exactly the same both times. My question is would the pulley size cause this to be under the rated ratio? And how should I get my results? I used the wand, engine running open throttle, no nozzle and filled a 5 gallon bucket for one minute. I scratched a mark at the water level and ran the test again and it filled exactly to the same mark. Then used a 2 gallon gas can (filled with water) to fill the bucket to my mark and calculated the results at 4.5 gpm…

Yes. Take a look at the spec sheet for this pump (now called the HP5535):

It’s rated at two different speeds, 1125rpm or 1450 rpm, producing either 4.5 or 5.6 gpm respectively.

So depending on the available HP from the motor, and the desired max PSI it could be setup to run at either speed.

I’m guessing your machine has the gx390? In which case, the manufacturer set it up for more PSI and less flow. Simple pulley swap should do the trick. You’ll get around 2,500 psi or a little better.

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First your going to need a tachometer some engines are set at 3200 3400 3600 and some run 3750 no load .
Measure the two pulleys then that will tell you your ratio .
Example
Engine pulls 3.5”
Pump pulls 7”
7 divided by 3.5 =2. This means the engine runs 2x the speed of the pump.
If the engine is set at 3600 your going to need a 2.5 to 1 ratio the get the pump about 1450rpm

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Ok going by memory I am not at the machine now… I have a 3 inch pulley driving a 12 inch pulley with a 420cc CHonda… Or 12 HP Chinese Honda…

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No it’s not a 12” you need to measure it again.
The best solution for this is probably a 2.2 to 1 gear box for about \$150 . Quick and easy to install and it will solve the issues

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Might it’ve been a 4” pulley? That’d put your ratio at 3:1, and bring your pump rpm right around 1150.

Edit: disregard. @florida_condo_cleani pointed out it wouldn’t be a 12” pulley.

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It’s a 3" driving a 12"

I know this isn’t an ideal setup but it’s what I had… I had the pump and cart with a bad engine I bought a Chinese Honda just to get it up and going… I do drive way cleaning on the side for my lawn customers… And may start doing some house washes to expand my business

That’s is a huge reduction. The cheap way out would be to replace the engine pulls and new belts . You old belts will be to short to work

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Wowza. We stand corrected. I’m thinking that your Chonda is running around 4000+rpm in order to give you 4.5 gpm. You should definitely get a tach and adjust it down to 3600 rpm.

Then get a 4” and 10” pulley for a 2.5:1 ratio. Or just bolt on the gearbox recommended above.

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Northern tool has cheap \$20 engine tacks

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I’m not concerned about pressure I just want more water volume…safely… I can make this pump last I maintain all my own equipment now and have some engines with over 3000 hours on them… It’s all about maintenance and giving a ■■■■…

Specs on that engine say 3600… but I will buy the tach

I know that when @SchertzServicesLLC built his Predator/Udor machine, his engine was running 4k+ from the factory. It was also supposed to be setup around 3500ish.

I like the combo hour meter/tachs. They can be had on Amazon prime for around \$15-\$20

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Someone must have had this thing set up for something specific… Would be my guess… I got it from an old employer…( we used it to clean farm equipment) He bought a new one after his new foreman let this thing sit out under the eaves of a pole barn for 3 years while I was laid off… I took it home and rebuilt the 11hp Briggs that was on it… Did a few jobs and it went through a flood at my old house… Hence the CHONDA…

Good idea… I’m a prime member!! I like the hour meter idea anyway… Have them on all my machines

I imagine.

If your Chonda was actually running at 3600 rpm, you would’ve gotten around 3.6 gpm from your bucket test

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Is there a chart you are getting these ratios from? Thank you for your knowledge!!

I’m just doing a bit of math off the spec sheets. But I think I might’ve slipped up on my last calculation.

You’re currently running a 4:1 reduction.

3600/4 = 900

The pump is rated at 4.5 gpm at 1125 rpm or 5.6 at 1450 rpm

4.5 gpm/ 1125 rpm = .004 gal
Or
5.6 gpm/ 1450 rpm = .0038 gal (round up to .004; close enough )

( basically what I’m doing here is calculating the displacement of the pump. For each revolution, the pump displaces approximately .004 gallons. Multiply that by your (supposed) operating speed, and you get the (supposed) flow rating. )

.004 gal * 900 rpm = 3.6 gpm

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