Cost to bore and hone Honda GX390 engine

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  #1  
Old 10-11-10, 06:10 AM
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Cost to bore and hone Honda GX390 engine

My friend left his pressure washer (Honda GX390 engine) outside for a couple of months and presumably had some water in the gas tank. He brought it to me seized. I disassembled the engine and found about 1 pint of water/gas mixture in the cylinder, muffler and carb.

Long story short, the bore is in bad shape - there was about 1/4" of rust/scale build up, preventing the piston from moving up the bore. Is it more cost-effective to bore & hone an engine of this size or does it make more sense to replace the block?

He is on a very limited budget so I floated the idea of buying one of those Chinese GX390 clones. I've heard good things about them and they're much cheaper than the Hondas. Anyone have anything to say about them?

Thanks,

- Joe
 
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Old 10-11-10, 09:09 PM
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I can't say much good about anything made in China. I'd be tempted to grab a used block on ebay.
 
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Old 10-12-10, 05:59 AM
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Wish there was one out there! The only GX390 block I could find was a new "Honda Style" GX390 block - probably a Stens or Chinese clone (or are they the same these days?).

It was only $50 so at least it minimizes my loses - I'll report back on the quality, etc of the block.
 
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Old 10-12-10, 11:27 AM
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Well, if one part has to be chinese, it might not be too bad for it to be the block. I think it has an iron sleeve. You get to retain your original innards, controls, starter mechanism, and carb...so you should be ok. Can you get the piston out ok? You'll need rings most likely.
 
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Old 10-12-10, 02:25 PM
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I cannot speak about the clone chinese motors under discussion but I recently got to experience a chinese made exhaust pipe expander - Large Tail Pipe Expander.

The fourth time it was used - all on the day it was purchased - the internal part which allows the item to operate shattered. The part that failed was a piece of solid steel. The metallurgy of the part was so bad that it failed when around 60 foot pounds of torque was applied through a 3/8" ratchet to the item. It was being used on a 16 gauge racing header while fabricating an exhaust for a race car. All I can say was the item was junk and an excellent example of the quality of items manufactured in China.

Best of luck and keep your fingers crossed.

Steve
 
  #6  
Old 10-12-10, 02:37 PM
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The piston is actually in surprisingly good shape - considering what it's been through. I have a set of Stens rings on order, along with a front crank seal, main fuel bowl (the old one was heavily rusted), and overhaul gasket set. I was able to remove the balancer ball bearing that was pressed into the crankcase by applying a little bit of heat and gently prying it out with a pain can opener. I took the time to lap the valves while the head was out as well.

Any other targets of opportunity I should take care of on this motor while it is all apart? I honestly don't work on Honda GX motors that often, simply because I rarely see them broken

Thanks,

- Joe
 
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Old 10-12-10, 09:41 PM
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I rarely see them broken as well. The things I would look for are wear in the rocker arms where the push rod fits in and where the rocker arm stud goes through and look for cracks in this area. You might also check the governor gear and make sure it is not loose-fitting and sloppy. I can't think of any real problem areas on these engines...they are pretty much the pinnacle of small engine quality.
 
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Old 10-28-10, 06:47 AM
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Just wanted to close the loop on this. Overall, the Honda clone block appeared to be good quality - all threaded holes looked OK - no missing aluminum, etc. The bore has a cast iron sleeve, just like the Honda block. The only major difference I noticed was the cast aluminum gussets in the clone block weren't quite as beefy as in the Honda block (such as under the oil sensor).

All of the GX390 parts fit in the clone block just fine though. Started up on the first pull (like a Honda typically does). Just need to break it in now.

I'll let you know if there are any long term issues once I get some hours on it.

- Joe
 
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