751 with 4 cyl Kubuto engine rough when warm

[salty]

I have recently purchased a 751 in need of restoration. Changed all the filters and glow plugs, starts OK but a bit smokey when under load. After 15-20 minutes when engine heats up it starts to run unevenly and bit rough. Under high revs it sounds a bit like it might be running on 3 cylinders. I haven't touched the injectors or fuel pump, diesel filter was very dirty before I changed it. Any ideas where I should start to look to resolve rough engine? I have been advised by local bobcat parts guy that it might need a set of rings as the air filter was also missing when I bought it.

 

[Tazza]

No air filter at all????
Thats not a good sign. If it was me, and had no air filter the first thing would be to remove the head and pull the pistons out and clean it all up. If it sucked in dust it acts like sand paper on the cylinder walls. You need to get the dirty oil out or it will just keep causing damage. A new set of rings may help, but depending on how much wear it may not too.
I would start with a compression test, see what you are getting. You should get up to 475PSI on a GOOD engine, anything close to 300 is quite bad, it starts to get hard to start and you will get smoke from un-burnt fuel.
Also, change the engine oil if you haven't already.
The other thing it could be as you said there was a lot of muck in the fuel filter, it could be your pickup screen is clogged. Is the primer bulb still round? if it goes flat, you have a restriction causing lack of fuel.

 

[jerry]

No air filter at all????
Thats not a good sign. If it was me, and had no air filter the first thing would be to remove the head and pull the pistons out and clean it all up. If it sucked in dust it acts like sand paper on the cylinder walls. You need to get the dirty oil out or it will just keep causing damage. A new set of rings may help, but depending on how much wear it may not too.
I would start with a compression test, see what you are getting. You should get up to 475PSI on a GOOD engine, anything close to 300 is quite bad, it starts to get hard to start and you will get smoke from un-burnt fuel.
Also, change the engine oil if you haven't already.
The other thing it could be as you said there was a lot of muck in the fuel filter, it could be your pickup screen is clogged. Is the primer bulb still round? if it goes flat, you have a restriction causing lack of fuel.

I bought a tractor years ago and found a hole in the hose between the filter and the carb, the compression was down so I overhauled it. there was .025 taper in the bores of the cylinders from dust.

 

[salty]

No air filter at all????
Thats not a good sign. If it was me, and had no air filter the first thing would be to remove the head and pull the pistons out and clean it all up. If it sucked in dust it acts like sand paper on the cylinder walls. You need to get the dirty oil out or it will just keep causing damage. A new set of rings may help, but depending on how much wear it may not too.
I would start with a compression test, see what you are getting. You should get up to 475PSI on a GOOD engine, anything close to 300 is quite bad, it starts to get hard to start and you will get smoke from un-burnt fuel.
Also, change the engine oil if you haven't already.
The other thing it could be as you said there was a lot of muck in the fuel filter, it could be your pickup screen is clogged. Is the primer bulb still round? if it goes flat, you have a restriction causing lack of fuel.

Thanks for the advice. The air filter holder and pipe to inlet manifold was still in position but no refill at all!!!! Bought the machine for €800 /€ 630USD so can afford to spend a few quid. Spent its life cleaning out poultry houses. I think the compression test looks like my next move. When I changed the oil and filter, the oil was in pretty poor state. You mentioned the pickup screen could be blocked, maybe stupid question but is it in the fuel tank? This is my first bobcat project so only learning. On the up side have the hydraulics working perfectly, had a blocked bronze filter and a leaky pipe. Worked that one out (bronze filter blocked) from your previous posts on the forum. The machine is one of the older 751's. The serial number plate is damaged so cant make out the number. Is there a serial number anywhere else on the machine. I know the newer machines have one stamped on front above the chain case. Will let you know how I get on with compression test.

 

[Tazza]

Thanks for the advice. The air filter holder and pipe to inlet manifold was still in position but no refill at all!!!! Bought the machine for €800 /€ 630USD so can afford to spend a few quid. Spent its life cleaning out poultry houses. I think the compression test looks like my next move. When I changed the oil and filter, the oil was in pretty poor state. You mentioned the pickup screen could be blocked, maybe stupid question but is it in the fuel tank? This is my first bobcat project so only learning. On the up side have the hydraulics working perfectly, had a blocked bronze filter and a leaky pipe. Worked that one out (bronze filter blocked) from your previous posts on the forum. The machine is one of the older 751's. The serial number plate is damaged so cant make out the number. Is there a serial number anywhere else on the machine. I know the newer machines have one stamped on front above the chain case. Will let you know how I get on with compression test.

The screen is at the end of the pickup tube in the fuel tank.
There should be another serial number just above the chain case. Lift the arms and it should be seen just above where the arms touch the chain case.
I assume it has a Peugeot engine? XUD9 or has it been changed over to a Kubota?

 

[salty]

The screen is at the end of the pickup tube in the fuel tank.
There should be another serial number just above the chain case. Lift the arms and it should be seen just above where the arms touch the chain case.
I assume it has a Peugeot engine? XUD9 or has it been changed over to a Kubota?

It has a Kubota engine so must have been changed over at some stage. I checked the engine serial number and it tells me its a 1997 engine. I have checked the screen in the fuel tank and guess what, its missing! Getting a lend of a compression tester so will see how it goes. Engine is still starting very easy in the morning with 30 secs of glow plug and no smoke unless under a heavy load, its only after 15-20 minutes when engine heats that the trouble starts, runs uneven and smokey. I suppose it takes that time for engine to heat up to proper operating temperature and then you see the real state of your engine, rings etc. There are loads of XUD engines available over here in Ireland from scrapped Peugoet and Citroen cars and parts are readily available in comparison to kubota, but I heard Peugeot engines were not very successful in Bobcats. I got 285,000 miles out of one in a Peugeot car a few years back so had no complaints.

 

[ddsprint]

It has a Kubota engine so must have been changed over at some stage. I checked the engine serial number and it tells me its a 1997 engine. I have checked the screen in the fuel tank and guess what, its missing! Getting a lend of a compression tester so will see how it goes. Engine is still starting very easy in the morning with 30 secs of glow plug and no smoke unless under a heavy load, its only after 15-20 minutes when engine heats that the trouble starts, runs uneven and smokey. I suppose it takes that time for engine to heat up to proper operating temperature and then you see the real state of your engine, rings etc. There are loads of XUD engines available over here in Ireland from scrapped Peugoet and Citroen cars and parts are readily available in comparison to kubota, but I heard Peugeot engines were not very successful in Bobcats. I got 285,000 miles out of one in a Peugeot car a few years back so had no complaints.

sounds like the motor is just wore out, like was stated earlier, compression test will tell, which one is it, a 1702, 1902 or 2203, for about 2k in parts and machining you build a new motor, 400 for machining and 1600 in parts, pistons, rings, bearings, gasket, the parts are not the cheapest, but it is a deisel, I will say that they are not that hard to rebuild, just a thought, let us know your route or decision, thanx

 

[ddsprint]

sounds like the motor is just wore out, like was stated earlier, compression test will tell, which one is it, a 1702, 1902 or 2203, for about 2k in parts and machining you build a new motor, 400 for machining and 1600 in parts, pistons, rings, bearings, gasket, the parts are not the cheapest, but it is a deisel, I will say that they are not that hard to rebuild, just a thought, let us know your route or decision, thanx

one other thought that might be your problem is that one of the injector is shot, those injectors spray out a mist at high pressure, and when there shot that is it, as stated in another thread, i had some kid check mine at a diesel shop, and looked like a guy taking a piss with more than one stream, junk, might want to get them pressure checked, there is no spark, compression, heat and fuel, thats a deisel, let us know what happens, thanx

 

[salty]

one other thought that might be your problem is that one of the injector is shot, those injectors spray out a mist at high pressure, and when there shot that is it, as stated in another thread, i had some kid check mine at a diesel shop, and looked like a guy taking a piss with more than one stream, junk, might want to get them pressure checked, there is no spark, compression, heat and fuel, thats a deisel, let us know what happens, thanx

Think I just found my problem, looks like head gasket is gone or crack in head. Was checking water level and it was down slightly and oil in the water. Did the compression test and compression if fine. Over 400 on all cylinders with no big change between cylinders. Will pull out the engine and open it up.