Seized Honda GX 390

[Richard001]

My guess would be you have a broken rod.

Well that certainly was my first thought, but the OP reports that the piston moves when he rotates the crank.

Richard

 

[Red Horse]

Well that certainly was my first thought, but the OP reports that the piston moves when he rotates the crank.

Richard

correct

 

[tomplum]

Sounds sumpish to me...

 

[guyina4x4]

I read on the internet honda engines don't fail?

Take it apart it takes like 5 minutes. Then you'll know.

 

[Red Horse]

Well guys finally had the time to pull the head. Valves intact. Push rods straight. I last worked on this in May and poured PB Blaster in spark plug. top of piston was crudy. Like sand. Again crank turns but will go forward and backward to TDC but will NOT rotate 360 degrees. As one valve responds to engine rotation, but other one doe not, do I assume lobe broke off cam nd that i what is preventing 360 rotation and beyond???

 

[fried1765]

Pull the plug and spray an ample amount of WD-40 in the hole. Get on the shaft with channel lock pliers and work it back and forth to try and free. Once it's free spin it over to expel the excess and give it a try. I have done this with engines that seized both from sitting and over heating. The last one was on a log splitter a few years back and the owner told me the other day it was still running fine.

Throw the WD-40 stuff in the trash!
To free up rusted components use only Kroil.
It really works!

 

[Grumpycat]

Well guys finally had the time to pull the head. Valves intact. Push rods straight. I last worked on this in May and poured PB Blaster in spark plug. top of piston was crudy. Like sand. Again crank turns but will go forward and backward to TDC but will NOT rotate 360 degrees. As one valve responds to engine rotation, but other one doe not, do I assume lobe broke off cam nd that i what is preventing 360 rotation and beyond???

If you can not rotate 720° then you can't really conclude one of the valves is not working.

 

[Red Horse]

If you can not rotate 720° then you can't really conclude one of the valves is not working.

Ahh--wasn't thinking-correct! I'm getting "Intake, compression", or "power, exhaust" and I wasn't sure which side was the one that was working. so what can be broken that is precluding full rotation?? Would have to be lobe?

 

[dirttoys]

Ahh--wasn't thinking-correct! I'm getting "Intake, compression", or "power, exhaust" and I wasn't sure which side was the one that was working. so what can be broken that is precluding full rotation?? Would have to be lobe?

Was wondering about this one. Something hung up in the cam drive gear?

best,

ed

 

[ericm979]

A lobe breaking off the cam would be very unusual.

More likely a valve is stuck open or a cam follower broke or there is something wedged in the cam drive gears/chain.