Over the last few months i have been gathering Kubota engine and generator bits and pieces to make one gen unit. GL7000 and a engine only from APU. had block bored for oversizes pistons ring bearings, etc. This is a two cylinder only . Wish I had room for a three. Parts for these are really expensive. A few more days and hopefully it will be running. Start up guidance is what I am looking for. Maybe other members have rebuilt one of these . I really do not want to messup now after all this work and money. The net down load gives good rebuild help but NO start up tips.
How much will a head gasket crush? The one in picture is0.050now. It will have a bearing on head to piston clearance. Book says 0.020clearance and piston is 0.023 above block at TDC. Is this consideres a normal amount of clearance or is this close?
My thoughts are to back gov. off so it runs at about 800-1000 . and varry speed a little by hand every so often. The Kubota book wants a new head gasket retorqued after 1/2 hr of run time. Do I do this hot or do I let engine cool down first?
What would be considered a safe amount of engine run time before I try the generator part and put a load on engine? This means bringing rpm up to about 3600 for generator to work proper.
How important is engine exhaust backpressure?--muffler from GL70000 will not work in new application. Was just going to put hose on for now get noise and smell out side and deal with muffler issue later.
What (in time) would be considered good breakin allowance?
How long until I change oil on fresh engine?
All start up pointers will be greatly appreciated. Both dos and don't. I will have water temperature and oil pressure sensors connected and IR gun. I think I wil leave engine shut down features diconnect for now. I just need to see this engine run for now and not be the third sc*** up Kubota to pass through shop doors.
Thanks Larry B
Larry B,
Sorry to hear about your 2 cylinder Kubota needing bored etc, am wondering how many thousand hours it has ? What happened to it ? KW rating, 7 kw, 58 Amp at 120 volts ?
I would run the half hour and re torque cold, double check valve lash, also agree on run it a while at about 1500 rpm area keeping eye on both oil psi and water temp, then bring up to your 60 hertz for a few minutes, than start adding load .25, then .5, then .75 and let run for half hour at the 75% load, Then go with the 100% load for a few minutes, just long enough to verify it can handle the load, (HP wise, oil psi & water temp), if all looks good & stable, reinstall it, close the door and enjoy.
Good luck
Dave M
Use break in engine oil and run it under load as soon as you verified it's got oil pressure and no leaks. Re torquing the head is an absolute must. The engine needs the load for the rings to seat correctly. At the Deere dealership we ran fresh rebuilds on the dyno at 100% rated output for 8 or more hours, sometimes they needed even longer. Break in oil was used for the first 50 hours at 50% load, then the recommended engine oil and 100% load there after. Generators are a bit different, but stepping up the load over the first 60 minutes is not a bad idea. It'll take a while to bleed the coolant system so keep an eye on that.
I'm about to fire up a fresh rebuild on my 8kw Westerbeke generator (as soon as the weather warms up a bit and it stops snowing). I plan on letting it run for 50 hours straight to break it in. Re-torquing the head and adjusting the valves is needed after the first couple of hours, after that it's full load while watching the oil pressure and temps.
Too bad there wasn't room for at least a 3 cylinder. The two cylinder is literally a 4 cylinder with 2 cylinders cut off. Hence, it runs rough. This is why low RPM won't be a good choice. I'd run at least 1800 if not more like 2500rpm. I had a truck driver friend with the Powertech 8kw 3 cylinder Kubota that when he sold his truck, had over 23,000hrs on the engine without overhaul. These engines are very long lasting. Run them up in the rpm so it gets warm and not build up carbon. Good Luck, TomC
It depend on the grade of Kubota engine how long one lasts they are not all equal
I normally count on .003" to .005" of crush on the non-crush portion of the gasket - the black part of your gasket. You should have enough piston to head clearance, depending on where you measured your .050". But different gaskets crush different amounts, I would either do a test (and waste a gasket), measure the old one, or get the crush spec from the manufacturer, which you can do with high buck racing gaskets.
Thanks for alll the replies. I can see from them that i would not have been running engine at a high enough rpm or adding load soon enough. I bought unit not running, it had 2700 hours on it, and after taking it apart I suspect the piston was hit the head. The piston was destroyed and so was cylinder wall. Reason for buying APU unit - to get a usable block..The piston has a letter 3 stamped in top. If I look at old head on the side that still had a good piston this letter 3 is faintly visible in the discolored dark part of head.
You may think I lost it after telling this. The cardboard box that the new piston-ring- wrist pin and pin bushing came in measures .020 thick. The same as my minimum thickness. I cut two piston size circles from cardboard, set on top of piston and bolted head on with old head gasket and torqued up. When front piston passed through TDC felt nothing. With rear piston at TDC a slight clunk was heard and resistance was felt. If you look at the pictures of the cardboard circles, the piston shape and letter 3 is noticible on both- but felt nothing on front piston.
Brian I measured at metal part. If I do same thing tomorrow with new head gasket and new cardboard rings would this be a satisfactory test for min clearance (.020") and find out gasket crush. Will measure black part before gasket install. Believing this engine went into self destruct from piston to head contact first time would like to avoid same thing this time. The second picture is old head gasket, metal 2 black layers with silver in middle
Thanks Larry B
cardboard picture missed-- try again
Just get you some old fashioned plasticine, put it on top of the pistons and turn it over once. the plasticine will squish out to the thickness of your gap. Measure the thickness of the old head gasket - if they are the same brand, that should tell you what the crushed height is.
Brian
Were you able to get the rear cylinder past TDC? If the rear cylinder hits the head, you should check the connecting rod for stretch and also check the crank shaft to make sure it's true.
Measure the piston to make certain it's identical to the front piston.
Next test would be to swap the conrod with the front cylinder and determine if it still hits the head. If the rear still hits with the front's piston and conrod, the issue is with the crank. If the rear piston and conrod hits in the front cylinder, then the issue is is that assembly.
Make sure conrod bearing shells are the correct thickness.
Keep us posted
Also check your methodology for measuring the height of the piston and make sure you do both. They can be tricky buggers, they rock all over the place if the rings aren't on or if the piston to bore clearance is loose. I use a depth mic along the axis of the piston pin, even then it can take a few tries to get accurate to .001".
Brian
I would check the deck height on that engine at both pistons
Quote from: luvrbus on February 25, 2015, 06:09:43 AM
I would check the deck height on that engine at both pistons
That's what I was thinking, too. If someone skimmed the headgasket surface on the cylinder (to maybe get rid of earlier damage from a blown head gasket) or put in an incorrect gasket where the cylinder meets the block, that will drop the head down closer to the piston. (I'm not familiar with these engines, but this is what I would have looked at with a similar problem with a motorcycle engine.) Measure everywhere, including length from piston top at Bottom Dead Center to headgasket surface on both pistons. If something measures up wrong, that will show you where to look next.
That being said, my WAIG is bent/stretched conrod or bent crank, probably. But check and measure everywhere.
(BTW, Brian mentions "plasticine" in his post -- in the US, we'd call that "modeling clay"; it works very well for this purpose.)
Is plasticine not a thing in the US? Who knew? The other old trick is to use a piece of lead fishing weight, like a little BB, but plasticine/modeling clay also lets you measure the exhaust piston to valve clearance, which makes sure the cam timing is set right. If the cam chain is off a tooth you can get the piston hitting the exhaust valve about 10 degrees BTDC on the exhaust stroke. Boy, it's a long time since I built an engine from scratch and had to measure all this stuff. 2008, the last formula ford engine I built.
Brian
It's called Plastigauge here it's been around since the 60's times have changed the first time I bought the Plastigauge it was 10 cents the last was 6 bucks a stick
Quote from: luvrbus on February 25, 2015, 07:37:17 AMIt'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).
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
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?
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
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
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.
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
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
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
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
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
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
Let's hope for a puff of black smoke then no smoke :D
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
By taking a ccouple of bolts out the rad will swing partly open
Too large contol panel to put in bay with gen
Plug in an lectric (analog) clock... with a minute hand, get a good watch or stop watch.
when the clock and watch get to 1 minute at the same time under load....the rpm/gov will be set properly.
2 minutes 5 minutes or 60 minutes then you know.
Do you need the plugs in, the panel should be easy to rebuild smaller without all the plugs you can mount the controller and regulator any where
All sounds good so far. Yes, a fresh engine will have what you described as crankcase pressure until the rings seat. Power will increase as the engine breaks in so the RPM drop won't be as much, but there will still be a fair amount.
I have my gen set for 62hz no load but it'll drop considerably under a heavy load.
Just a note: My 8kw will not start a 13k AC unit on one leg (rated at 33amp per leg). I rewired for 66amps 120 and it'll start and run both AC units just fine.
Regarding engine speed and Hertz:
Are you sure that engine is rated to run 3600 rpm? Most diesel gensets use a 4-pole alternator, which requires 1800 rpm to produce 60 Hz. I probably missed a post or two here and don't know the whole story, but I would'nt want you to damage your engine.
Donald:
Neat idea on speed-setting using analog clock.
X2 on the speed setting kudos.
to LarryB, the original poster:
How did this project wind up? Everything work out good?
If this is a synchronus direct drive alternator, then you use a hertz meter to determine engine speed. No load should be about 63hz. Full load no less than 59hz.
If this is a inverter, variable speed genset, then whatever the engine needs to run. Good Luck, TomC
Quote from: OneLapper on March 15, 2015, 08:25:23 PM
I have my gen set for 62hz no load but it'll drop considerably under a heavy load. Just a note: My 8kw will not start a 13k AC unit on one leg (rated at 33amp per leg). I rewired for 66amps 120 and it'll start and run both AC units just fine.
Mark -Too bad my time in CT was so limited, you probably could have helped me figure out my cantankerous genset!
:'(
Quote from: RJ on March 28, 2015, 09:11:44 PM
Mark -
Too bad my time in CT was so limited, you probably could have helped me figure out my cantankerous genset!
:'(
Hey RJ,
Yeah, too bad you didn't have a day or two to park at my place and spend some time sorting out the genset. I still think you'll need to rewire it to a single 120vac leg. I have had no luck running my 8kw unit setup on two 33 amp legs. It just doesn't handle unequal loads and will trip out when it tries to start either one of the AC units. When I rewired the head to a single 66 amp leg everything started to work as needed..... well, almost everything. I ended up burning out the head but I'm not sure if it was because it was wet when I started it, or that I dropped a small washer into it. Either way, sparks flew.
I'll send you a PM about the manuals, lenses and glass soon.