Kubota B7100 Overhauled now will not run

[Sanddog]

Without reading all thru the thread. Make sure the hyd oil pump is not building up pressure and stopping the engine. Make sure the 3pt lever is all the way down.

WILL CHECK POSITION OF LEVER, I THINK AM PRETTY SURE IT WAS IN THE CENTER (NEUTRAL) POSITION AND THE THREE-POINT ARMS ARE DOWN. if I UNDERSTAND THE OPERATION OF THE SYSTEM, JUST NOW CHECKING THE MANUAL, IN THE NEUTRAL POSITION THE HYDRAULICS ARE TO HOLD THE CURRENT POSITION. I WOULD THINK IF THE THREE-POINT IS DOWN THAT WOULD HAVE THE PRESSURE OFF THE SYSTEM, BUT MAYBE IT IS SOMEHOW TRYING TO PUSH THE ARMS DOWN. I WILL WORK WITH THIS TO SEE IF I CAN IMPROVE THE SITUATION.

 

[Sanddog]

Jumping in here late, but you have checked the fuel flow going into the injection pump right? Those symptoms sound like the ones seen when you have a piece of crud blocking the outlet of the tank.

Aaron Z

YES, HAVE REMOVED FUEL TANK AND CLEAN IT, REPLACED FUEL FILTER, AND ALL FUEL LINES. FUEL IS GETTING TO THE INJECTION PUMP AND SEEMS TO INJECTING WITHOUT PROBLEM. THE MOTOR IS DEFINITELY COMING UNDER SOME SORT OF RESISTANCE THAT IS CAUSING IT TO DIE.

 

[Eagleview]

YES, I DO NOT THINK IT HAS ANYTHING TO DO WITH THE GLOW PLUGS, BUT RATHER THE TIME DELAY. IT IS VERY INTERESTING THAT THE MAIN BEARINGS, WHICH CERTAINLY COULD BE THE PROBLEM IF NO HYDRAULIC ISSUES, WOULD COOL DOWN THAT FAST AFTER GETTING HOT ENOUGH TO SEIZE THE MOTOR.

You only have 1.5 - 2 thou bearing clearance , it wouldn't take much for the bearings to swell that much and get tight on the crank . It also wouldn't take long for that heat to dissipate from the bearings and into the engine block as they are a tight fit in the block .

Take the timing cover off and get someone to crank the engine over , I will bet money oil squirts out of the end of the cam as that plug is obviously loose .

Kubota 71 camshaft oil plug fix - YouTube

 

[bigdeano]

If you take the engine apart be sure to check the piston to bore clearance. Different piston alloys require different clearances. Maybe the machine shop got it wrong. The time involved seems about right for the pistons to heat up and drag. I had this happen with a car engine.

 

[D2Cat]

In your very first paragraph you tell how you "correctly" set the timing and added shims. I believe therein is your problem. On that engine the timing is set by the shims at the IP. The gears you lined up the dots on have to rotate several times to get them to line up. It's not, line up the dots and go.

Did you purchase your head from Kubota or aftermarket? That extra thin shim that came with the head gasket is for heads that have been milled off, and that shim gets that back to original height.

 

[Sanddog]

If you take the engine apart be sure to check the piston to bore clearance. Different piston alloys require different clearances. Maybe the machine shop got it wrong. The time involved seems about right for the pistons to heat up and drag. I had this happen with a car engine.

I described what is happening to the guys at the machine shop and they agree it sounds like the motor is trying seize up as soon as some heat gets generated. They have asked me to bring it back and they will recheck all clearances. Which is nice, but now I have to take it all apart again, bummer!!

 

[Sanddog]

In your very first paragraph you tell how you "correctly" set the timing and added shims. I believe therein is your problem. On that engine the timing is set by the shims at the IP. The gears you lined up the dots on have to rotate several times to get them to line up. It's not, line up the dots and go.

Did you purchase your head from Kubota or aftermarket? That extra thin shim that came with the head gasket is for heads that have been milled off, and that shim gets that back to original height.

When I took the engine down, I rotated it what seemed like 10 to 15 times but the dotes on the the timing gears never did line up exactly. It seemed like the closest they ever got is what I show in the first post. You say is it not just "line up the dots and go." I tried to follow the manual, but did not read anything other than to line up the dots per the picture in the manual. HOW IS THIS DONE CORRECTLY??? EXACTLY WHAT DO YOU DO? IS THERE SOME OTHER MARK, POSITION OF PISTON, ETC. THAT IS ALSO USED TO SET IT UP CORRECTLY?? THANKS FOR ANY HELP ON THIS.

The head is an aftermarket head. The machine shop had to clean up the seats to get it to hold a vacuum but otherwise it seemed to be OK. After rechecking the ring gap, I did add the thin metal shim and gave the intake valves a little extra clearance but as you have pointed out, the gears are off. I set the valve clearance at TDC on the compression stoke as specified in the manual. I watched the values as I turned the motor over by hand and the intake values are opening before TCD on the intake stroke. So, back to how to correctly install and align the gears?????

 

[Sanddog]

UPDATE

took the motor back down and returned it to machine shop. Based on the fact that it appeared to be seizing up after running a short time the guys at the machine shop said it sounded like the pistons, but after rechecking all of the tolerances on pistons, crank, etc. neither they nor I could find anything to explain the motor apparently seizing. The guy at the machine shop said to look down the line to see if anything is causing back pressure on the engine.

Before taking the engine down, I did remove the lines from the hydraulic pump to see if that was the problem, but could not tell any difference. I guess the input shaft going to the HST trans could be causing problems but I did keep the clutch depressed. I do recall the engine slowing down a bit when I let out the clutch, but did not seem to be sufficient to cause seizing of motor.

I had mentioned earlier a concern over the oil pressure, but do not think that is a problem. Upon disassembly, I found all bearing surface wet with oil. When the machine shop could not find any problems I began checking all oil passages and found they had placed the missing oil galley plug back in the wrong hole. It was blocking the port for the oil pressure sensor, thus the reading of no oil pressure I had just before tearing this thing down.

DOES ANYONE HAVE ANY SUGGESTIONS AS TO THINGS TO CHECK BEFORE PUTTING IT BACK TOGETHER AGAIN???

 

[bigdeano]

Can you turn the hydraulic pump by hand? Doesn't seem likely it would be seizing up though.

Did they tell you how much clearance the pistons have? I wonder if the pistons are hypereutectic alloy or not.

This is like a murder mystery on tv. Probably no fun for you though.

 

[Sanddog]

Can you turn the hydraulic pump by hand? Doesn't seem likely it would be seizing up though.
YES AS I RECALL, THERE IS NO RESISTANCE WHEN LINE DISCONNECTED. NOT SURE WHAT IS HAPPENING WHEN EVERYTHING IS CONNECTED.

Did they tell you how much clearance the pistons have? I wonder if the pistons are hypereutectic alloy or not.

THE MANUAL CALLS FOR ABOUT 0.003 INCH AND THERE IS 0.003 TO 0.004 ON EACH CYLINDER. I HAVE NO IDEA WHAT EXACTLY THE PISTON ARE MADE OF AND I BOUGHT THE OVERHAUL KIT FROM KUMAR BROHERS ONLINE. THE PISTONS LOOK FINE AND FIT WELL IN THE CYLINDERS. I GUESS THEY COULD BE REALLY EXPANDING BUT THE MACHINE SHOP GUYS DID NOT THIS WAS THE PROBLEM AFTER EXAMINING THE PISTONS WITH ME HAVING RUN THE THING QUITE A FEW SHORT CYCLES UNTIL IT DIED. THERE IS NO OBVIOUS VISIBLE SIGN ON THE PISTONS AND ANY OF THE BEARING SURFACES THAT THE MOTOR WAS ACTUALLY SEIZING.

This is like a murder mystery on tv. Probably no fun for you though.

THE FUN HAS DEFINITELY GONE OUT OF THIS PROJECT!! HOWEVER, I AM VERY CURIOUS TO FIND OUT WHAT IS CAUSING THE PROBLEM, SO I AM NOT GIVING UP ON FIXING THIS THING.