kubota engine rebuild

[Oonrahnjay]

It's called Plastigauge here it's been around since the 60's 

      In England, it's not the same thing.  "Plasticine" over there is modeling clay, like you find in a kid's toy store; that's actually a trade name like "Kleenex" but it's what everyone calls what we call modeling clay even if not made by the "Plasticine" company.  "Plastigage" over there (and I expect the same here) is a precision thickness and width plastic material in strips that's firmer than modeling clay.  Plastigage is calibrated so that you can clamp it in between bearing surfaces and something like a crankshaft and read the clearance by measuring the width; the precise width gives you a reading of the precise thickness (or clearance, as the case may be).

[Larry B]

thanks again  LARRY
   A lot of the things you mention I have done. The crank I held in lathe and steady rest and with dial indicator measured for bent crank. Lathe in neutral and turn chuck by hand. I had 0.001 on center bearing - book said up to 0.002 was ok. The crank has new bearings and they where within spec. by book. this includes con rod bearings. I have new pistons (.25 metric over- about.010") rings, wrist pins and wrist pin bushings. Made a piece on lathe to push out old wrist pin bushings and install new. These felt really good after install. The machine shop did a real good job of boring the block and touch up valves and seats ($150.00)  The new rings where right in middle of book spec when measured in block bore. I do not own a depth gauge. To measure piston above block- set a piece of key stock on top of block , zeroed dial indictor and turned pistons through TDC. and watch dial Front .022 , rear.0235 - (different by .0015). I just asumed that to be a reasonable amount of diff.  Right now I do not know how I could measure bottom dead center with a dial indicator only, to compair con rod lenghths. The rods I am using are out of the APU unit. This engine was still running(sort off- just plain wore out) but did not have a melt down like the other when i found. This morning at  shop having a coffee and wrinkling my forehead while looking at this engine I found a small piece of paper in plastic bag of gasket kit that mentions a shim for head gasket-- what are they talking about?? The book says piston to head clearance should be. 0197 to .0279-- The timing on this engine is gears with marks. I have checked a couple times It is on punch marks.   With engine together  crank, bearing, pistons with rings installed and valve cam and injector cam in place youcan easyily rotate and can not feel any tight or loose spots. Going to go back to shop and maybe switch pistons per hole and check heights again. I have a lot of double parts-- cranks,cams, gears, injectors and inj. pump-- so i can do a lot  of part switching---I think something is wrong with this head to piston clearance.   When I had cardboard between piston and head I could turn past TDC both holes,just tight on rear hole. 
    Thanks again  for help    Larry B   

[OneLapper]

If the crank is true, and the pistons are new, and rings are new, I think the difference is in the connecting rod.

The "shim" the note mentioned is most likely a head gasket shim...... because the piston hit the head for the last owner.  If you have an extra engine you can measure all the connecting rods and see what the lengths are.

BTW, are you using an OEM head gasket?

[brmax]

What brand is the gasket kit your using, I really am curious also with the oil pipe coming up out of the block in front does yours have that recessed for an o-ring and did you get one if.
Thanks

[luvrbus]

Don't you need to shim the head on most Kubota engines ? I got into one where it was 0.065 it took me a month to get 0.022 on it now this guy has the opposite problem

[brmax]

I thought on some of the 4 cylinders you could get a thicker head gasket if the project had the deck surfaced, but I suppose in all cases the valve height/stickout is checked also. Really wanted to mention that new oil o-ring is Kubota orange from the old blue and a higher temp than the normal also many kits come with a o-ring that's simply to thin.

[Larry B]

Thanks for all the helpful hints. This morning I decided to take engine apart and switch cranks. Maybe the rod throw on one crank is shorter than other. The second choice crank (the one that got install today) did not have as smooth a finish to the bearing journals. It is straight and main clearances are better than first crank. While things are apart I will measure rods and do comparison tomorrow-- have three. All parts and gaskets are bought from Kubota like engine is made in Japan. The Kubota parts person I talked with yesterday could not give a definite answer as to cranks being same or different. The part no.s are diff but that does not mean they are not interchangable. The engines are 20 plus years apart in age and kubota does not always cross ref 20 year old to tier 3 which one engine is. There was no " shim" listed for 20 year old engine. Thanks for heads up on O ring. The gear cover case with O rings will not likely be used as that put oil filter in back corner so will likely use gear case that brings filter to front side. I looked today they do look thin. I had to get more plastiguage for things day and when I requested the silly putty or play  dough stuff for piston to head clearance checks I got a look like ---what planet is this guy from-- so I just paid for my stuff and shuffed out the door. 

    Larry B

[bevans6]

Try "Toys-r-us" for the modeling clay...  Or make some dough from flour and water like my mom used to do for us fifty plus years ago...

Brian

[luvrbus]

I bet he gets sooner or later the Kubotas are good little engines they are just so touchy you get the clearance off by a couple of 1000th they will run but will blow the white smoke.

I don't know about his 2 banger never worked on one but on the others if the head or the block has been resurfaced you shim those or use a different gasket BTDT.

I know of a 3 cylinder that was just rebuilt that is smoking like crazy he tried to save a few bucks and had a non Kubota shop rebuild it and they didn't get it right not even close   

[Larry B]

  Today things went a little better. Changing cranks lost.0025 piston protusion through the head, so I gained that much more piston to head clearance. The .020 piece of cardboard will pass through TDC on both pistons now and does not leave an imprint like before.  I measured the three  rods and the two I am using are the same but the one from the newer(GL7000) engine is .002 longer and the crank throw appears to be .0025 longer. One would almost think the block should be taller. Is it possible the rod could be stretched? Shouldn't the firing or detonation compress not stretch the rod?  .This GL7000 engine took a good beating before it quit.  So I guess it is carry on and try and get my rebuild to make some black smoke or blow up. Thanks for listening to me through my many moments of frustration.
    Larry B

[Lostranger]

Larry, thanks for starting this thread. I'm about to rebuild a 2 cylinder Yanmar for my ThermoKing Tripac, and your experience is helpful. I've been a little intimidated about starting, and I find your perseverance inspirational.

Jim

[OneLapper]

Connecting rod stretch is an issue on some of the Porsche racing engines I've played around with, but not on a 1800 or 3600 rpm diesel engine.  A bend rod is about all I can imagine for damage on a small diesel.

It makes sense that the crank shaft is bent. 

Keep at it and let us know how it runs!

Mark

[luvrbus]

Let's hope for a puff of black smoke then no smoke 

[Larry B]

    The engine is running  , everything seems to be OK. I have had engine running for about a week but between fishing, the little things, and coffee drinking buddies time passes. I ran engine 1 hr with 5amp grinder on each leg of 240 plug, then 10 amp grinders on each leg for two hours. Today I used 2-1500 watt hotplate heaters,(one per leg) and ran for 3 hrs. Before starting gen I plugged a heater into shop wall plug just for reference guide, on gen. Voltage went from 121.6 to 114, (was not expecting that much drop). Extension cord was 12 gu. 
       On gen. get 117 volt @ 3100rpm --no load
                    get 115 volt with one heater on one leg---still 3100rpm
                    get 112 volt a heater on each leg   ---rpm dropped to 2850
    turned gov. up to 3100rpm  after plugging heaters in and get 115 volt reading, run like this for three hours. During this time, oil sat at 40psi and water 180F at top of thermostate outlet point. As point of interest I have a 90F temp. drop between top and bottom of rad. Hope it works that well in bus.  When I initally started engine there was some blue smoke at exhaust, after about five hours running it is nearly gone. The valve cover air breather had a lot of air flow at start, this also seems to be getting less. Would this be from rings not being seated yet and pressuring crank case? Another coffee buddy --that's it for today. When I disconnected loads my rpm went to 3250 and voltage to 117.5 Now I need guidance again. Should let you know when it comes to computers and AC elec. I am very challenged. We do a lot of camping with no hook up so my main goal will be to run two roof top ac unit to cool bus for night sleeping. So want gen to handle these and set correct and not burn them or gen. up. (Dometic-- 15000btu)
   - Do I need to increase the load during run in? Have some 500 watt quartz lights
    -How close to the max. 3600 rpm do I get? I have cut the lock wire on gov. set bolts and increased quite a bit from orig. To get 115 volts with two 1500 watt heaters the engine goes to 3250 when load is removed..
   -Where should hertz be set? How close to 60 do I need to get? Do not own a clamp meter. Recommend a reasonable clamp meter that measures AC & DC amps and hertz. 
   Took some pictures but will post on next page as I do not want to loose all this typing due to oversize limit. The contol panel needs to  be remote from gen as I would not be able to get door open in old ac bay. Need to sort out remote start from contol panel. Need a different muffler as the one in picture could not be hung under bus. Will check for Dometic elec needs tomorrow.   
     Thanks   Larry B

[Larry B]

By taking a ccouple of bolts out the rad will swing partly open