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PostPosted: November 29, 2015, 6:08 pm 
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Trying to lighten the flywheel.
In first gear the kubota revs up at the same speed as in neutral.


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PostPosted: November 30, 2015, 12:38 am 
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You can balance the flywheel yourself. You just need a close-fitting shaft to go through the middle and a couple of reasonably level, straight edges - a couple pieces of angle iron are fine.

Just remove metal until the flywheel stays wherever your position it. Long before that, you'll be below the limit a spin balancer can see an imbalance. Once you get the flywheel balanced, bolt the pressure plate to it and balance that.

I have a Stewart-Warner spin balancer, but I also have a mandrel-and-straightedge setup I made (with bolt-on bob weights) to balance externally-balanced flywheels that people bring in without a crankshaft. Your Kubota appears to be neutral balanced, so you don't need a bobweight.


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PostPosted: November 30, 2015, 6:05 am 
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These engines are externally balanced by the crank damper and flywheel, so in this situation, he can't balance without having measured and made a bolt on weight to static balance before machining.

The dynamic balancer for aircraft props he used on the first page to balance the running engine is a great tool, but very expensive. A perk of being a General Aviation Mechanic!

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PostPosted: November 30, 2015, 9:22 am 
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Interesting. I've never seen an inline-three with external counterweighting.


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PostPosted: November 30, 2015, 6:29 pm 
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The block side of the flywheel has a series of deep, large diameter holes; all on one side, close together, and out near the ring gear. They can't be seen unless the flywheel is removed.

Jim,

It looks like you would have hit the balancing holes during the milling process. It also appears you have milled away the alignment dowel locations. How will you center the pressure plate?

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PostPosted: November 30, 2015, 7:50 pm 
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I'm still a quarter inch away from the lightening holes on the backside of the pressure plate.
I am going to cut away that section on the backside of the pressure plate to lighten it up even further.
I left the sections extra big (the huge gear teeth I tapped into for the pressure plate bolts)so I can remove some of that for future balancing.
As for the dowel locations Jack had just advised us to drill the existing holes in the outside of the pressure plate oversized.There were no dowel pins.
Jim


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PostPosted: December 1, 2015, 8:59 am 
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Picture of the old way of lining up the pressure plate.


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PostPosted: December 1, 2015, 12:38 pm 
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I've got it down to 16 pounds.


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PostPosted: December 1, 2015, 12:53 pm 
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If you remove the stop solenoid the engine will run until you pull the stop lever (the little forward one)


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PostPosted: December 1, 2015, 6:46 pm 
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I would have made dowels and drilled dowel and bolt holes, but that's me.

The dowels locate and support the pressure plate in shear, with the bolts only as a clamp.

The low rpm and power along with limited use make it less critical imho, but it seems it would be very easy to drill the holes slightly too big, resulting in the pressure plate being in a slightly different position each time it is installed, throwing off the balance, even if it were indexed and reinstalled in the same position. This may be why you had more vibration than Jack experienced with his engine. Since the spring is under pressure when teh bolts are installed, the only way to check would be with a dial indicator to check the runout, though you can't get to the pressure ring so it would be against the case.

If you might try using bolts long enough to have a solid shank and shorten them as required, countersink the flywheel for clearance, then with the runout acceptable using the old bolts, use a rotary file to adjust a hole at a time to accept the shank of the new bolts tightly.

Just my observation.

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PostPosted: December 1, 2015, 7:03 pm 
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We use a diesel in a different application and learned the hard way just how sharp the torque pulses are - they can shear bolts. In addition, when shutting down the engine, the high compression makes the engine stop so fast that it can snap parts/shafts/bolts if there's momentum downstream.

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Last edited by KB58 on December 1, 2015, 9:15 pm, edited 2 times in total.

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PostPosted: December 1, 2015, 7:52 pm 
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I hear what you guys are saying but the way Jack did it he went over 100,000 miles and haven't had a problem yet.
Of course my lightened flywheel will not dampen out the pulses like the heavy one so I may have a problem.
I think I left enough meat to install dowel pins next to the bolts. I will have to wait till spring I packed everything up for the winter storage.in


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PostPosted: December 2, 2015, 6:34 pm 
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If you decide to add dowels next year, the correct size is probably 6mm, so at least 20mm long for better than 60% engagement with .375" protruding. However, you've oversized the holes to .250" using the drill bits. Not much difference in cost either way at less than $10 for a bag of them from Mcmaster in metric or standard. The listed sizes are actually plus sized to ensure an initial press fit. There are also dowels designed as replacements that are plus plus assuming the holes are oversized.

I don't remember how light mine is but I also have no pressure plate, which is probably about 20 lbs. I just hope it isn't so light that it won't idle.

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PostPosted: December 12, 2015, 11:27 am 
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Mv8 do you know of a 6 cyl common rail car injection system that we could use half of and install in a Kubota?


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PostPosted: December 12, 2015, 12:03 pm 
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I like the kubota for it's reliability, simplicity, and low power. There are many more powerful but heavier diesels including Kubotas own line for refer units, which are popular swaps into jeeps, rangers, s10s, etc as well as vw diesels into the suzuki samurai. There are several sources for adapters. Just pick your power level / consumption rate.

For modification, you might try vw, audi, or volvo. I think Bosch is on the 5th or 6th generation of common rail, so it has been around (at lower fuel pressures) for a long time.

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