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Hi all
I purchased a Vermeer stump grinder with a Honda GX620 on it. I knew the motor had problems and would like some help and direction before I tear it down.
The motor had thrown and bent a push rod 3 years earlier and the thing was abandoned and left in the rain for a period of time.
Water in oil so I dumped that, fresh fuel, plugs, filters and gave it a compression test.
120psi pot 2
60psi pot 1
First question does this have a decomp on pot 1
Anyhow thought a run would help so fired her up. 2 minutes or so and all good, then pang pang pang pang pang. Shut her down, sounded like a valve seat or something high up. Pulled rocker covers (po had replaced push rod) and found the collet thing that sits on top of the exhaust valve is loose in the head. Undid rocker arm, replaced collet, set to .15 and .2 on both pots. Was sure I had found noise but no, fired up and same valve noise on no1.
Pulled no1 valve train, one guide is showing a bit of wear and a slight bend and the guide has been a bit butchered.
Pulled no2 valve train and all good.
With rocker gear and spark plugs out the motor turns over but if you approach tdc on no1 it has a tight spot just before it. Could this be the decomp if it has one?
The pang noise also sounds like a valve but I’m guessing it’s every revolution like a 2 stroke so probably not the exhaust or intake valve.
Wondering if this tight spot is the cause of the pang noise.

Yep every time no1 hits tdc, just before it make a clack if you free spin the motor by hand. This could be the noise, also had a look and the pushrod is only just bent, I’ll order one of these and the guide is bent back into shape .

Valve guide pictured, been a bit mucked up but I can’t see the rod or guide making this noise.

Must have been the inlet valve that let go, nice new bits but guide and rod not replaced????

It’s got a click with the rods out

Run the piston to TDC then just a bit past so it is on the down stroke.
Use a torch through the plug hole to check this
Then press down on the piston.
If it moves down , even the tiniest bit then the big end / gudgeon pin is gone
Double check by pressing down hard against the piston while rotating the engine.
If the click stops then it is pull down time.

Good idea Bert, piston pin and big end seem fine. Still have this binding problem just before tdc, thinking it’s time to pull the side cover and have a look.

Have the heads been removed from this engine. If not then I would start there since there could be something stuck to the head causing the binding. Throttle butterfly screw comes to mind.

Heads have not been removed. Uncanny thinking mate. After being left in the rain the carb was seized, I ordered a new one and when I pulled the old one the butterfly fell out on the bench. Could well be a bit of metal mashed to the top of a cylinder.
What’s easier to pull, head or side cover?

I would pull the head since there is a butterfly screw embedded into the top of the piston or head.

surely there is enough piston head clearance for a butterfly screw? I’d expect it to have pinged out the exhaust valve, could be stuck under a valve.
The more I think about it the more I think decomp off the cam, but yes should probably bite the bullet and pull the head or side cover.

When it was left out in the rain anything could have been dropped down the open mouth of the carb

Langdon19 said:

Heads have not been removed. Uncanny thinking mate. After being left in the rain the carb was seized, I ordered a new one and when I pulled the old one the butterfly fell out on the bench. Could well be a bit of metal mashed to the top of a cylinder.
What’s easier to pull, head or side cover?

Click to expand...

They're both about the same....
Sidecover probably

Langdon19 said:

surely there is enough piston head clearance for a butterfly screw? I’d expect it to have pinged out the exhaust valve, could be stuck under a valve.
The more I think about it the more I think decomp off the cam, but yes should probably bite the bullet and pull the head or side cover.

Click to expand...

Its happened on a few inteks. Taryl fixes all mentioned that on youtube. It hammered the piston and pinched the rings so it was smoking like a son of a gun.

I would pull the head first.

The landlords Kohler managed to swallow a screw from the carb butterfly.
It had been getting harder & harder to start for quite a long while
We were amazed when I shoved the bore-a-scope down the plug hole & saw the moonscape

Did you see the man in the moon?

Small piece of magnetic metal stuck to head
Could be a spark plug electrode but who knows

Piston

Anyone know what this is? Heavy for its size and magnetic

Probably not a butterfly screw, I think they're usually made of brass (?)
Could be plug electrode like you said....
?

Scrubcadet10 said:

Probably not a butterfly screw, I think they're usually made of brass (?)
Could be plug electrode like you said....
?

Click to expand...

Most are steel since you can pick them up with a magnet. The screw wouldn't be that big and would of left a thread pattern in the head

Most likely a lump of gravel that fell in when a plug or air filter was off.
Slight change it could be a little piece of the alternator magnet so worth pulling the flywheel and checking just to be on the safe side.
Alternator magnets rarely fall out when they break up usually they will clump together.
However if one is falling apart then it will take out the stator and even the rectifier.
Remember it is a stump grinder so will be tossing around a lot of debris.

Thanks all, I’m going to pull the inlet manifold and make sure it’s free of debris. Hopefully get to grind my first stump soon.