Kubota G5200 - Page 3

Sam Mac · #21 11-26-2015, 07:47 PM

The more I look at this one the more I'm leaning towards the cam timing being off. I looked through the manual for both the D600 and the WG640 both are pretty much the same engine. Anyway the cam has a key between the cam and the gear. Just wondering if it sheared the key or if someone has been inside and screwed up. How much oil did you have to add to it before you tried to start it? These things hold almost a gallon of oil so maybe it was not run out of oil at all. You also said you had it running, it ran good and you shut it off. Hard cranking could also be caused by the timing being off. I listened to your video and did not hear any horrible sounds like a roached bearing or rod rap. I looked in both manuals and the Cub parts site and did not find a shim for the head, just a head gasket. You'll notice that all 3 cylinders show equal marking from the valves, to me if it crapped a main bearing and rolled the shell the marks would be more pronounced in 1 cylinder. If it was me the engine would be on the bench and first place I'd go was under the gear case at the front of the engine.

No matter what the problem is you need to do some exploratory surgery to find out what the problem is. Good luck and keep us posted.

Alvy · #22 11-26-2015, 08:40 PM

Quote:

Originally Posted by Sam Mac

Hard cranking could also be caused by the timing being off. You'll notice that all 3 cylinders show equal marking from the valves, to me if it crapped a main bearing and rolled the shell the marks would be more pronounced in 1 cylinder. If it was me the engine would be on the bench and first place I'd go was under the gear case at the front of the engine.

No matter what the problem is you need to do some exploratory surgery to find out what the problem is. Good luck and keep us posted.

X2 and what others have said about mechanical timing being off. And I think Sam meant to say rod bearing instead of main but either way yes, slim chance of all 3 rod bearings taking a poop at once

Sam Mac · #23 11-26-2015, 08:53 PM

Quote:

Originally Posted by Alvy

X2 and what others have said about mechanical timing being off. And I think Sam meant to say rod bearing instead of main but either way yes, slim chance of all 3 rod bearings taking a poop at once

I meant to say mains but the rods are also about the same when it comes to an oil problem. Mains on these are priority oiling so they get oil first, then the rods and then the cam bearings from what I can see in the manuals.

105_Tom · #24 11-26-2015, 09:07 PM

This whole ordeal has been beating me up pretty bad. I have a buyer that's supposed to pick it in the morning for a price that will easily put me in the clear for what I have into this tractor. If I can talk him out of the deal, ill pull the motor and the timing cover and hope that the answer is in the cam gear. But I'm pretty sure the tractor will be gone, because the buyer has rebuilt several Kubota engines and is pretty confident that it simply jumped time. The remainder of the oil I initially drained out of the motor showed no signs of grit or discoloration, and it ran too good before I pulled the head and tightened up the top end. The weak spot in the top end appears to be the rocker arm studs, which have enough yield to flex the rocker arm as you saw in the video.

We'll see what happens tomorrow morning when the buyer comes... I hate to leave a job unfinished.

Billy-O · #25 11-26-2015, 09:41 PM

The real reason I think a possible cam timing issue may be true is that looking at the pictures of the cleaned engine in post #5 is that I see a lot of prior mechanical work done on the motor. I see chipped paint on bolts and gasket lines and galled metal on some bolt heads. This motor has not had an easy life and somebody fooled with it.

J-Mech · #26 11-26-2015, 10:01 PM

Tom,
Sure wish I wish I was closer to you. I would have gladly taken that project off your hands.

I still am really doubting a timing issue. Too bad we will likely never know the outcome.

Should have kept it. Too good a deal to abandon ship on.

105_Tom · #27 12-20-2015, 09:36 PM

So, I finally heard back from the buyer. He pulled the timing cover. Everything looked ok at first. He rolled the motor over and got all of the timing marks to line up. Or so it appeared. He went to pull the cam, and it seized after slightly moving out of the 'home' position. Now he's got a stuck cam and in the process, pulled the gear off the end of the cam. When that happened, he saw stress marks around the keyway where the notch had gave ever so slightly as a result of the oil starvation to the cam and the resulting stress on the rotating assembly. That would explain the slight retarding in the timing - not enough that it wouldn't run for me prior to pulling the head, but just enough that the exhaust valves couldn't get in the clear fast enough to avoid being kissed by the pistons.

He said he'll keep me posted on the progress. He's gonna fashion a slide-hammer type of something to the end of the cam and try to draw it out that way. Then he'll see how bad the cam bores are scored, and decide if he can hone it and throw a used cam back in, or if its too trashed to continue. I personally think he's gonna be ok with a little hone job. Still mad I let this one go without tearing into it more.

Stay tuned...