GX390?

I have a Honda GX390 on a 3700 psi pressure washer. I'm getting hard to start after it's set for a few months and I'm not getting any younger. Once I get it started, it's easy to restart. I crank the water pressure adjust to minimum and pull the trigger on the wand to remover load from pump.

Just wondering if perhaps the valves aren't set right? I've read one place the intakes are .02-.04 and exhausts are .08-.010. Does this sound right?

Also read the engine has auto decompression that operates off the exhaust valve. So if the exhausts are not on the money, could this be why it's hard to start?

Engine has a low oil pressure switch. Is it possible that I don't have enough poop to get the motor turning fast enough to build oil pressure? Once the oil is warm, it's easier to start. Should I try a thinner oil? What grade?

Does anyone have a flywheel with starter teeth and a starter? Love to have electric starter.

Does anyone have other ideas I could try?

Seriously thinking of buying a new pressure washer with electric start.

There are about 4 different pumps on the market. What's your favorite?

George

(quoted from post at 20:51:15 10/15/12)
Engine has a low oil pressure switch. Is it possible that I don't have enough poop to get the motor turning fast enough to build oil pressure? Once the oil is warm, it's easier to start. Should I try a thinner oil? What grade?

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The low oil switch is a Oil level sensor, not pressure. If that is the issue, rocking side to side will usually get it going. You could also try bypassing the switch if you keep an eye on your oil level.


390s are a big engine to pull by hand.

RGMartin,
For some reason, I thought the sensor measured oil pressure. I have a 20 hp kohler that I'm sure it's sensor measures pressure, because every time I change oil and filter, it takes a few more cranks before the engine makes a spark. Once I goofed, pulled the choke to start the enging after changing oil, About 10 cranks later the spark arrived and shot fire out the muffler. One BIG BANG.

Because the 390 doesn't have an oil filter, you may be right. What tells the sensor there is the presence of oil if it doesn't use pressure?

You're right, it takes a lot to crank a 390. My right arm is still hurting.
George

The 390 has a splash lube system. No oil pump so no pressure. The level switch is the only oil protection it has. The Honda switch is more reliable than most.You can unplug it and see if it makes starting any better.But I don't think that is your problem.

How many hours on the engine,is compression good, valves set properly.

If you are like me. The main problem is age. Ain't as young as we used to be.

Almost forgot. Valves

Intake 0.15 MM
Exhaust 0.20 MM

Billy, thanks for the info.

Bought pressure washer used. It has no hour meter. As for compression, YES, that's what makes so hard to start. Sometimes it fires too early and pulls the starter out of my hand.

Going to check valve clearance and put a thinner oil in it.

George

Billy,
Checked valve clearance. Both were close. Tightened the exhaust perhaps .001-.002 inches. Nothing major. However, I did notice what Honda called using the exhaust valve as a decompression valve. When I rolled the motor over slowly, the intake valve open and closed. On the compression stroke, the exhaust valve opened a small amount and just breifly. Then on the exhaust stroke, the exhaust valve opened even more and stayed open for a longer time.

How does Honda do this? I'm guessing it has 2 lobs on the exhaust cam. Or is there another way to get the exhaust valve to open briefly on the compression stroke just while you are starting the engine? Wouldn't this send a small amount of fuel/air mix out the exhaust before there is a spark?

Do other small engines do the same thing making it very critical to keep the exhaust valve clearance spot on the money?

Thanks,
George

George. Those are cold settings. The cam lobe controls compression release. No other way that I know of. Briggs has the same system.I should have the 390 manual somewhere around my nice clean office.I will check.

Billy,
I adjusted the valves when cold. Exhaust was only about .002 in out. I did notice the exhaust valve opening a little on the compression stroke? Does the cam do that? Are there 2 lobs on the cam?
George

The cam has a weight that is on a lever. That lever turns a small shaft that has an eccentric on the end of it. That eccentric sticks out into the exhaust lobe of the crankshaft. The weight it held one way with a spring. So at low speeds the eccentric will open the exhaust valve a little at crank speeds. When the engine hits and comes up to running speed the weight over comes the spring pressure. Then the eccentric is flush with the cam lobe and no longer hits the exhaust valve.

Have you tried a new spark plug. I have a JD pressure washer that has a Honda motor on it. If it starts hard it usually is the spark plug not firing right under compression. Also are you able to crank it good and fast??? As my Dad has gotten older he can't pull the rope fast enought for small engines to start correctly. He complains about this one or that one not starting correctly. Me or my sons can just give it a good yank and the engine starts fine.

I have actually mounted a few snow blower motors on some of the things he uses with a small gas engine on them. The snow blower motors have 110 volt electric start on them. So he can just plug in the cord and hit the button and away he goes.

One of his motors was the same model as one used on snow blowers. I was able to change the flywheel to one that would use the electric starter.

George----I have an 8hp pressure washer---about the same as your GX390. I have the same issue with it. What makes it hard to pull is that you're pulling against water pressure. What I do is lay the wand down on the ground with something to hold the trigger open. Makes a lot of difference. Also use a leather glove to pull the rope. (Redneck solution!!)

JDseller,
I'm looking for a flywheel and starter. I think my problem is I'm getting old. 3 days later my arm and sholder is still hurting from pulling on the starter.

May buy myself a new pressure washer with a starter for Christmas.

My 6.5 briggs on a pressure washer is a dream to start, but the gismo that adds soap and bleach is broken. It's built into the pump. I would have to buy a new pump to fix the problem. I need to do something, still have 3 properties to clean.

George

It could only be that the carburetor is starting to get gummed up due to intermittent use. I would try a fuel additive/stabilizer. I prefer Seafoam, but there are others that are just as good on the market. I tend to also get the ether out and give it a shot or two so that it starts on the first pull.