Brand new gx630 smoking and knocking

I bought a brand new pressure pro GX630 5.5gpm/3500 psi machine and everytime I try to put any of the nozzles that came with it (besides the soap tip) the engine billows smoke and has even knocked. I can soft wash with my jrod all day, but if I want to put a 0, 15, 25, etc. All hell breaks loose. It does the same thing when I connect my surface cleaner. Anyone have any suggestions or ideas? The plumbing passed the bucket test and it bypasses into the tank beautifully. No leaks. 50’, 100’, 200’ hose doesnt matter. Downstream injector working properly. Engine has full tank and fresh oil.

Id be contacting the manufacturer.

check the oil level. did the machine get tilted or turned over…

What color smoke ?

Black smoke. The engine hasn’t been tilted. No excess oil or low oil. It runs great until I put a tip other than soap on. I emailed water cannon but would love to fix this my self.

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White and grey is usually oil black is usually un burnt fuel. If it’s new I honestly wouldn’t touch it. That being said start with your spark . It is possible that the oil got sloched around in transport but that would clear up very quickly.
Knocking can be spark timing or a bad bearing. Neither are likely on a new engine.


Ok thank you. I’ve contacted the manufacturer but the first thing I did was take the wheels and handles and battery off an bolt it on a trailer on top off thick rubber and really dont want to have to put it all back together and send it back. I’ll start with the spark thanks.

This is a very inexpensive and

somewhat accurate way of testing spark


One of those, a test light, and a $10 multimeter. Necessary tools for any of us to have.


Stupid question, have you checked the choke :rofl:

That was my thought too, choke. Sounds like it doesn’t like any load being put on it. The tips could be the wrong size for the machine too, maybe for a 3200/2.5gpm?

I also did a google search, one guy found out the stock Honda oil dipstick lies, it had too much oil in the crankcase. Should be halfway or below on the stick.

If it’s running ok to DS but smoking and bogging with pressure tips maybe the tips are wrong. You should have #6 pressure tips and 2503s or 25035s for your SC tips with 5.5gpm/3500psi. You could also adjust your unloader with correct pressure tip until only a trickle is coming out bypass hose.

That’s not a stupid question, I did check the choke i thought maybe it was stuck or linkage messed up.

I tried the tips that came with it that are 55’s and the #6’s i ordered from pressure tek. Both sets cause the same thing

I run 2535s in my surface cleaner and #6 tips even though the machine came with a set of 55’s.

Well the upside is, it should be under warranty. I’d find a Honda warranty repair shop and let them look at it. It’s probably something simple. That’s usually the case. Let us know what is going on with it

I just got home from work this morning and checked again and there is a pool of gas sitting under the air filter so maybe a carb or main jet problem?I’ve had the battery on and off during set up so maybe the fuel cut solenoid is involved. Hell I don’t know.

That’s true. I’ve reached out to the manufacturer I’ll call the shop today. Thanks for all the help!

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