Honda gxv620 waterlogged, seized, now low compression

[youngbuck$]

Work trade for a generator gone bad. $1500 in hard labor got me a no run generator. Only had half an hour on it but had sat outside a while apparently took quite a bit of water through the muffler. I put some diesel down the cylinders but didnt realize they were chalked full of water. Wiggled her loose gently but i should have just taken off the jugs.. Anyone got recommendations on where to go from here? Wont start and i been spraying and turning quite a bit. If i pull the jugs will i need a gasket set. Is it possible rings are fine just stuck in grooves? Got 55-60 psi compression. No carbon in cylinders just a lil rust in the one on side of muffler opening. Thanks for your insight

 

[nolids]

You probably bent the rods. Next time pull the plugs and spin the engine to get the water out.

 

[youngbuck$]

You probably bent the rods. Next time pull the plugs and spin the engine to get the water out.

No i did pull the plugs and turned it back and forth real gentle adding oil and gas until it freed up. Would bent rods give me low compression? On both cylinders? Like i said the one side on the muffler opening side was worst and at bottom of its stroke holding all the water and rust where the other piston seemed to be in pretty good shape. Maybe you meant i should have pulled the valve covers and rods then freed it up. That is probably true shucks. Ill pull em now.

 

[frank_]

decompressor affecting your compression readings maybe ? if not you probably need to remove the heads and hone the bores

 

[youngbuck$]

It seems to me both of yall are speaking mumbo jumbo. Does a gx620 even have a decompression valve?any older members?

 

[frank_]

its usually a spring loaded finger that slightly jabs the exh valves open on startup you could temporarily open up the valve clearance to avoid the finger

 

[Deleted member 117362]

It seems to me both of yall are speaking mumbo jumbo. Does a gx620 even have a decompression valve?any older members?

You may be correct, stuck rings, or stuck valves. I would soak engine again for a day or two and see if compression came up. May just be time for a tear down.

 

[youngbuck$]

its usually a spring loaded finger that slightly jabs the exh valves open on startup you could temporarily open up the valve clearance to avoid the finger

View attachment 783348

Oh alright then i'll check that out.oh my this thing is heavy guess ill slide her in the cabin on snowboards. Might have to make a video

 

[youngbuck$]

Did i mention this thing only has 1/2 hr on it? Sorry if not the best pics and background i'll get on that today.god it wud be cool if i didnt f#!= this thing up already

 

[youngbuck$]

Man when yall reply u aint just bullshittin. Right right right i should already know. But duce you are rightest: time for a teardown ,and this is my first big v twin, oh boy. But first... time for some genny sledding! Ill edit with a url to the video of me mushing this beast, hiya! Come on have a lil fun once in a while!

 

[jr27236]

I would load the cylinder up with penetrating oil. Let it sit dump the crankcase and refill with proper level and rotate slowly. If nice and free spin up with with the electric starter (sure it has one) or a drill on the flywheel nut.
While soaking go through carb. Also im sire the flywheel magnets and coils have rust on there surfaces that needs to be cleaned. Keep posting updates

 

[youngbuck$]

Phew! Ok well soaking wasnt smoothing crap out. So i went ahead and tore it all down which wasn't a cakewalk, especially when concerning removal of the powerhead from the engine, which involved tapping new threads in the end of the crankshaft and pressing the tapered shafts apart. Next up i gotta open up the crankcase which i pray doesnt have too many more surprises in store for me. The cylinders were coated with some rusty dried oil crap that is insanely hard to remove,naptha seems to be most effective and i tore up my cyl. hone on the #1 already where as the #2 wasnt so bad. It's a safe assumption that its gonna need new rings. I dont have a dial caliper.SHOULD I ORDER OVERSIZED RINGS?specs say 77mm bore is stock. I broke the screen on my smartphone but i'll try and upload some photos with it anyways. ALSO CARB HAS BEEN MODIFIED FOR LP WITH SPUD TYPE, should i upgrade to dual fuel kit or get another carb as backup for gasoline. Thanks for your input

 

[RealRusty]

So, what was the outcome on your GX620 project? I'm in the midst of a similar GX620K1 low compression puzzle. This was on a generator given to me by my father with the diagnosis that the cam gear deteriorated. Yes, getting the generator head disconnected from the engine was a ***** and included tapping threads into the shaft and getting creative with a puller and slide hammer. Indeed the plastic cam gear was toast. Replaced it, along with all the internal plastic parts because come to find out this engine overheated to a point of shutdown which eventually lead to the plastic cam gear exploding. While at it I pulled the heads to decarb, and the top end looked to be in pretty good shape - I could still see hatch marks on the cylinder walls. Buttoned everything up only to find very low compression in both sides (30# in cyl 1 and 60# in cyl 2). Thinking I got the timing wrong on the cam gear, I pulled the rockers off so the valves wouldn't open but still low compression (and yes, these engines do have an exhaust valve decomporessor on the cam lobe). Pulled one head off and opened the crankcase again and pulled out one cylinder for inspection. Cylinder bore specs out within tolerance (worth having a dial gauge, even a cheap one), as do the valve stems and guides, the head is not warped, and the valves seats and faces are in good visual shape and contact properly (per Prussian Blue contact test). The only part close to service limit are the valve springs, being just shy of needing replacement. The intake valve was heavily carbed on the intake chamber side (high altitude operations on propane?), and when I poured cleaning fluid on top of the valves the intake valve leaked through with springs still in place. So, thinking I'll lap the valves, put in new springs and stem seals, and put it back together. I still need to spec the piston and rings, so might end up doing a ring job while at it. Any other thoughts on what to check for the source of low compression?
Thanks
Rusty