Honda GX620 clacking noise

[Langdon19]

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.

 

[Langdon19]

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 .

 

[Langdon19]

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

 

[Langdon19]

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

 

[Scrubcadet10]

It could be in the head, but usually a connecting rod will click just before TDC also.
but take that with a grain of a salt.

 

[Langdon19]

It’s got a click with the rods out

 

[bertsmobile1]

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.

 

[Langdon19]

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.

 

[ILENGINE]

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.

 

[Langdon19]

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?