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 12-25-2002, 09:30 Post: 46560
chris leesmann
2002-12-25 09:30:09
Post: 46560
 kubota B6100HST 4WD engine knock

I had recently purchased this with a bad engine,#2 rod bearing failure. purchased used crank and totally overhauled the rest of engine.now it runs fairly good but, lots of black smoke on start up and pretty much goes away at wot and after warm up can here slight miss or (like lean miss in gas engine).at wot.at idle a very distinct knock noise and as throttle is opened noise disapates.With stethescope the loudest spot is fuel line from pump (fuel)not injector). oil pressure good,injectors overhauled,I think fuel is good #2 diesel.all air appears too have been bled.I don't believe it too be engine noise or bearing failure.I double checked valve adjustment.Head was not milled and clearence appears ok.Then after a cople of days of running and checking all of a sudden trans oil starting foaming or bubbling out of shifter boot only when stationery.Now with brake applied seems to have stopped.3ph goes down very slow with pushing but comes up very fast.I looked for lever under seat but not there.Engine seems to run good when driving and trans performs normal.Can anyone disifer this problem? sorry so long. Thanks chris Marthasville Mo.






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 12-25-2002, 19:43 Post: 46572
buckmaster



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 kubota B6100HST 4WD engine knock

This is my original message.I have since joined the club.Didn't no was this easy.So I hope now someone will read and help.I can almost fix any kind of car problem but havn't had much experience with diesels if at all.
thanks buckmaster






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 12-26-2002, 05:41 Post: 46585
TomG

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 kubota B6100HST 4WD engine knock

Sounds like several problems.

Since there was a recent engine overhaul, I wonder if the engine timing can be assumed correct? Usually that's a matter of matching marks on gears under the timing gear cover, which would take some tear-down to verify visually. Injector pump timing is another matter and the timing should be verified. A manual should give procedures. Some procedures may require an injector to be removed and use of a dial indicator. Valve clearances affect injector spill timing and I guess we're assuming they're correct.

I'd describe my Ford as having moderate gray smoke at startup and some smoke until it's warm. There is knocking right at startup that diminishes within a minute. I think these things are normal for diesels. I can't tell from the description if what is experienced might be normal or not.

I'd check the TX oil level. An overfilled TX is a possible explanation. Another possibility is water or other contamination in the oil, so changing it on general principal isn't a bad idea. It's also possible for obstructions or leaks in the hydraulic pump suction line to introduce oil into the oil that could produce froth that bubbles out around the shifters.

There often are two o-ring seals on shifter shafts, so it might take a lot of frothing to bubble oil out the top if the seals are in good condition. If seals and boot are in bad shape and the tractor sat outside, then that's a good way for rain can get into a TX, so maybe that's an explanation.

Many tractors have a flow control valve somewhere under the seat. These valves adjust the rate of fall of the 3ph but doesn't affect the lift rate. It sounds like a flow control valve is fairly closed--as would be normal when using a heavy implement.






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 12-26-2002, 09:59 Post: 46592
Art White



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 kubota B6100HST 4WD engine knock

For what's been done I think Tom has some good points to begin with.






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 12-26-2002, 17:13 Post: 46602
buckmaster



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 kubota B6100HST 4WD engine knock

Thanks Tom for responding!I checked and double checked the timing marks because I performed the overhaul.The reason I checked so many times is this!When I disassembled the engine there is a total of 5 gears;oil pump,not timed,crank gear one mark,idler gear 3 marks injection pump gear one mark,and camshaft gear1 mark. the injector pump gear and idler gear never were removed and stayed mesched the timing marks on these gears never would line up always fell 2 teeth short every 3rd revelution ie: 3cylinder.I removed the idler gear when reassembling to turn shaft to allow all 4 timed gears to line up.This was a concern when assembling and I checked all the resources availible to me to double check alignment.Is it possible the injector pump has a problem that could have started the original #2 rod bearing and cylinder pitting and now still exsists.And the noise could have been covered up by the rod?
thanks, chris {buckmaster}






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 12-27-2002, 07:23 Post: 46617
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 kubota B6100HST 4WD engine knock

On my Ford 1710 there is an adjustment for something called the injector spill time. That's the one I especially wondered about. Adjustment requires positioning the engine and removing a delivery valve and then loosening a coupling between the pump and its drive shaft. The pump is rotated until it just starts delivering fuel at the correct engine position. I know that a spill time that is off will make an engine smoke.

I also know that the mounting position of a pump affects the spill time and procedures for removing and replacing a pump often require making an index mark across the pump body and engine so it can be replaced in the same position. Mounting a new pump usually requires a spill time adjustment. However, some old Ford farm tractors have a scale on the pump calibrated in degrees and owners sometimes just changed the settings to see what worked the best.

I'll think through the knocking buz some, but I'm mostly gas engine experienced and diesel engine theoryed myself. When I've rebuild gas engines, I'd check the crank journals with micrometers to see if the diameters and out-of-rounds were in tolerance. I'd also check the bearing clearances at 90-degrees with plastigauge. I don't know if something like that was done, but it would eliminate a possible explanation for knocking.

Bad injectors or nozzles can cause knocking. I've heard of people identifying problems by slightly loosening injector line fittings while the engine is running. If the knock disappears, they've found the problem. But since this is theory for me, I don't know what else the test might reveal. Of course extreme care must be taken when working around a running engine. In addition to the usual hazards, loosening injector lines (running or not) exposes a person to fuel under high pressure. If it gets injected under the skin, amputation is a usual cure. Same goes for testing for hydraulic line leaks with fingers. Nobody can recommend that somebody else carry out this type of procedure.






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 12-27-2002, 15:54 Post: 46625
buckmaster



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 kubota B6100HST 4WD engine knock

I also read about cracking the injector lines to isolate wich cylinder I think I'll try that tonite to see if it might be #2 cylinder again.And yes I plastigauged every bearing after micing all journals and all checked ok because I only wanted to do this once.I'm thinking the black smoke at start up and the knock are the same problem but also at wot there is what I would call on a gas engine, a lean miss with a small puff of black smoke each time.At all other throttle setigs engine purrs as if no problem.and really atwot it sounds good.The noise is at idle only and slightly to about 1/4 throttle then you don't hear any noise.






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 12-28-2002, 08:49 Post: 46641
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 kubota B6100HST 4WD engine knock


Sounds like the right sorts of things were done. I'd guess the wrist pins etc. also were checked. Some manuals don't specify hot or cold for valve settings, but I think cold is more common for diesel tractors.

In terms of the knock, a comparison with the sound of another engine would be very helpful. The sound might be normal, but I don't think that puffs of black smoke are normal.

Diesel trouble shooting often distinguish between black, gray and white smoke (blue is oil like in gas engines). When I hear 'black smoke' I usually think of too little air or overheating, which is the same thing. Too much fuel also is black if it's ignited or white otherwise. A diesel usually puffs some gray until it comes up to operating temperature and many continue puff a bit while rmp is increasing when a lot of throttle is added. I think I'd change the air filter and check for obstructions and maybe give it fresh fuel and make sure it's coming into the normal temp range just to check these things off. I'd also verify the spill-timing, although it it's a little off it should make gray smoke, or white if it's really off, rather than black.

I guess this is a flock of little things that are pretty to check before turning to checking out more difficult problems. There could be a bad injector, compression loss, a governor problem that gives poor fuel metering at low rpm, and the ugly list could go on and on.






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 12-28-2002, 12:51 Post: 46653
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 kubota B6100HST 4WD engine knock

I guess my post here did not show up. Some of what I said has been covered now.
Last year a friend of mine got a Chev diesel crew cab that had the engine damaged. The owner had taken it to Mr. Goodwrench to set the injector timing (spill timing). When we took it apart it had burned completely through one cylinder and damaged the rod and head. The timing is critical to performing correctly and you need to know what you are doing to set correctly.
It ran fine once we had it back together.
Peters






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 12-29-2002, 07:10 Post: 46670
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 kubota B6100HST 4WD engine knock

Eventually the net on this problem will start closing and we'll figure it out. Still a pretty wide net though but some things will start being checked off pretty soon I imagine.

Peters: I was harping on the spill time setting because as you noted, the procedure is complex and could produce some of the problems. The procedure for my 1710 requires taking off a valve stem keeper so the valve sits on top of the piston and then using a dial indicator on the valve stem to set the piston to a speced degree BTDC. Chris hasn't described doing something like that but maybe he has or maybe there's another way of setting it on his Kubota.

A couple of things that I guess are still widening the net are: Weak compression on one cylinder can make an engine run cool for that cylinder. It may puff exhaust but may warm up enough so that it wouldn't puff if running under load. A compression test might show something.

The injectors were overhauled. I hope that a good assumption is that they're OK and the pressures were set. Puffing on one cylinder sure could be an injector. I don't know if the injector overhaul included the delivery valves that are usually thought of as part of the pump. Delivery valves are mostly check valves, but they do produce a sharp pressure drop at the end of injection. Without that drop the injector nozzle dribbles, and I'll bet a dribbling injector would make exhaust puffs at low rpm. I don't know how commonly delivery valves fail though or how to check them. I guess that's why diesel shops have test gear.






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Discussion Boards > Active Subjects > Messages as Posted > Kubota Review Forum

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Art White 1 | buckmaster 5 | chris leesmann 1 | DH83 1 | Peters 1 | TomG 5 |




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