Just ordered this tach. Hardline Products HR-8061-2 Hour Meter/Tachometer for up to 2-Cylinder Engines https://www.amazon.com/dp/B000FOOAXY/ref=cm_sw_r_cp_apa_i_Qq6gCbZ2SED01
Will look at the direct drive or resizing pulleys after the holidays
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Looks like the one I’ve got on my snowblower. Nice little unit
Wow so yeah this thing is over reving? No wonder these Chondas don’t last … people probably never check that… Rex told me these things don’t last because people over do the rpms
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Well, that along cheap parts and poor production tolerances. The overreving certainly can’t help any 
Yeah it’s all luck of the draw anymore… production quality isn’t what it used to be with anything… It’s all sold out to the lowest bidder… I have seen the same motors I get 3000 hours out of last 1,000 or less with good maintenance schedule… So cross my fingers that Chin Ho was having a good day at work when he assembled mine… LMAO
What site?
That’s envirospec . I haven’t ordered from them in years . They still email me every day. That was from yesterday
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I stand corrected. I’ve never seen a pulley that big except on air compressors and sprayer pumps.
If you switch the engine pulley to a 4.75 or 4.80 or 4.85 whatever is easier to find you will get 5.6 gpm out of the pump with the engine running at 3600rpm
It’s possible you may be able to move the pump back enough to use the same belts if cost is the main objective. The pulley should be less than $50 for an H bushing type and less than $20 for a standard pulley with locking key way
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Hey @Infinity…so your math made me curious about my setup. I currently get 6.6gpm from a gear-driven HP5535 with a gx390. I plugged in the numbers from my set up into your formula.
3600/2.2 = 1636
5.6/1450 = .004
1636 x .004 = 6.55gpm…which is right on the money
I’m taking it my gx390 is overreving a bit? Would it be best to get a tach and bring it down to 1450 or is a gx390 ok to run a little hard? I ran it all year like this and it was fine…never gave me any trouble. But I’d also like it to last as well.
Maybe you could stop over sometime, I’m near Lowe’s on Ridge Road. I live on Lake Worrell… cost isn’t a big factor im just not a full time washer… Maybe if things pan out… but for now this is a test unit…
If I follow correctly, you’re over-driving the pump, but the engine rpm is spot on. The gearbox doesn’t provide enough of a reduction to run the pump at the rated speed.
I’m not really sure how damaging it will be for that pump to over-drive it on a constant basis. The pump is turning roughly 15% faster than it’s meant to.
At the very least, you should probably plan on maintenance and repairs to happen on a somewhat more frequent basis. Instead of changing oil every 500 hours, perhaps do 350-400 hours. And cut the life expectancy by a similar factor
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Got it. Makes sense. Thanks
Pumps don’t have set rpms only advertise popular specs . As long as the input hp doesn’t change most pumps can run up to 2000 rpm . You bigger body pumps like tsf2021 and ones like it have no problem even at 1850 for 9gpm@3200
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That’s fascinating. So theoretically, someone could take the ever popular 5.6@2500, change the pulleys to run it at 2000rpm, and they’d have an 8@1700ish?
Depending on how difficult the pulleys were to install, and the belt to adjust, it might make sense to do a temporary swap if I landed a condo cleaning job and wanted some faster rinsing for a few days. (Practically nobody has their flatwork cleaned around here, so the lack of pressure wouldn’t be a concern.)
If your planning on doing that call tech support first and give them your pump information. They have a formula that can tell you what is ok and what is to much.
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So I could get 8gpm with my pump?
Effectively 1500 psi at the end of the hose?!
Each pump is different best thing to do is call your pumps manufacturer tech support . Some pumps have to much rotating mass to turn high rpm . Others will have flow restrictions because of port size. If your pump only has 1/2 intake water would have to move to fast to fill the head .
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There are guys running 8gpm pumps on a gx390 through a reduced gearbox. There’s a few posts on the forum here you can look up. It would be awesome for house washing. This guys is running a General 2221 on a gx390 and is getting 1600 psi…probably less through the hose. He’s cleaning pavers at a quick pace.
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Good video. I’ve watched it before. It looks like his sc is under sized for 8 gpm. Seems like he is using his arms to keep it from flying. 
