Kubota B5100 smoke

Smagner234 · Aug 15, 2016

Hello,
I'm new to this site/forum and I am need of some advice. I have a b5100 that I bought a year ago and noticed recently that there is some white smoke apparent when running. I grabbed a pyrometer today and measured the temp of each cylinder on the manifold and found the cylinders to be about 40 degrees apart, 141f and 187f. Does this variance mean I have a bad injector? Could that be leading to the smoke? I don't burn coolant so I think the head gasket is fine, but I'm a bit lost as to what might be causing the variance / white smoke.
Any help would be greatly appreciated.

torch · Aug 15, 2016

Smagner234 said:
Hello,
I'm new to this site/forum and I am need of some advice. I have a b5100 that I bought a year ago and noticed recently that there is some white smoke apparent when running. I grabbed a pyrometer today and measured the temp of each cylinder on the manifold and found the cylinders to be about 40 degrees apart, 141f and 187f. Does this variance mean I have a bad injector? Could that be leading to the smoke? I don't burn coolant so I think the head gasket is fine, but I'm a bit lost as to what might be causing the variance / white smoke.
Any help would be greatly appreciated.

White smoke = unburnt diesel. Cold cylinder suggests no fire there. Hows the compression on the low temp cylinder compared to the hot cylinder? Any blow-by out the crankcase vent? Another possibility is a bad glow plug.

Other possible causes such as clogged air filter, bad fuel or injector timing should affect both cylinders equally.

torch · Aug 15, 2016

Another thought: does yours have a decompression lever? Perhaps it's stuck open on the cold cylinder?

Smagner234 · Aug 16, 2016

Thank you for the advice, I will check out the decompress knob this evening. I did look at the crankcase vent tube and did not see anything coming out of it. I placed my finger over the tube and did not feel any pressure while my finger was covering the tube or see any fume once I removed it. I will test the glow plug this evening with my multi meter and let you know what I find. Thanks again!

85Hokie · Aug 16, 2016

Smagner234 said:
Hello,
I'm new to this site/forum and I am need of some advice. I have a b5100 that I bought a year ago and noticed recently that there is some white smoke apparent when running. I grabbed a pyrometer today and measured the temp of each cylinder on the manifold and found the cylinders to be about 40 degrees apart, 141f and 187f. Does this variance mean I have a bad injector? Could that be leading to the smoke? I don't burn coolant so I think the head gasket is fine, but I'm a bit lost as to what might be causing the variance / white smoke.
Any help would be greatly appreciated.

I have measured my cylinders too, the further from the fan the hotter it gets.
I cannot remember the numbers, but if yours fall inline with further from fan, I would think it would be somewhat normal.

bucktail · Aug 16, 2016

Are you sure about the head gasket? I used to get a little white smoke out of mine when the glow plugs weren't working, but that was starting. Once it's running, the smoke should be black unless there's hardly any compression, in which case it would only be running on one cylinder. That should be noticeable. Did the muffler somehow get filled with water and it's just steaming off? Seems strange to me. I suppose it could be the injector, but I would think that an injector functioning that badly would basically have it running on one cylinder.

Smagner234 · Aug 16, 2016

I checked the glow plugs tonight and they tested 1.9 ohms and 2.1 ohms. I assume that this is close enough to be in spec. I didn't check the compression yet, I will hopefully do so tomorrow evening. If the compression is ok then I would assume it's an injector issue?
The tractor is kept inside and the muffler is free and dry. I recently replaced the air filter and fluids. All fluid levels are to factory spec.

D2Cat · Aug 16, 2016

Since it's so easy to do, I'd check the valve lash before remove any injectors. Do you say the decompression know was returning completely so the valves are closed?

Might put some Stanadyne additive in the fuel at a concentrated level for a while to see if any difference is made.

If you take the injectors out to test compression, you just as well take the injectors to a diesel fuel injection/pump shop. They can test the spray pattern and the pop off pressure and usually do not charge much at all...some don't charge for these test.

If they need some attention I would purchase all new ones from a dealer, like Coleman. http://www.colemanequip.com/Kubota_Parts.asp

North Idaho Wolfman · Aug 16, 2016

What D2Cat said!

Smagner234 · Aug 17, 2016

Hi Thank you for the tip on valve lash. Admittedly I did not know what valve lash was, however one you tube video later and I'm on the same page. haha
What is the required spacing between the rocker arm and the valve tip? Also, any tips on how best to complete this procedure? Is it common for the valves to need adjustment?

Thanks again

D2Cat · Aug 17, 2016

Double check with a manual, but I'm pretty sure valve gap is .008 with the engine cold, for both intake and exhaust.

If you have a feeler gauge with .008 on one gauge, that's what you need, if not find two that total .008. That should slide under the rocker arm above the push rod and not be loose or tight. Just slide in there with a no slop.

You can probably turn the engine over by reaching in and moving the fan. May have to hold the belt snug. When the valve gets to it's highest point is where you want to be.

A little practice and you'll see how easy it is. The only way to make it easier is to have a glow plug or injector removed from the cylinder. Don't remove them just to set the valves.

Smagner234 · Aug 17, 2016

Thank you very much! I will do that this evening and let you know how it works out.

Smagner234 · Aug 17, 2016

So I checked the valve lash and I'm glad you mentioned I should because this is what I found. Working from the radiator towards the gas tank the valves were at .014, .010, .009, .007. The manual says to gap them between .0059 - .0074, so I gapped them all to .006. I fired the tractor back up and there was unfortunately still some white smoke. I checked the decompression valve and it was definitely off or closed. I removed the cap on the valve cover and noticed that there was some white smoke coming out. I could only see the smoke when I angled my light just right. With the naked eye and normal light you can't see it. Not sure how much smoke indicates blow by. I am planing on doing a compression test tomorrow and I'll be honest I'm not looking forward to it. Haha
I attached a video of the smoke coming from the valve cover, is this blow by and if so how severe?
Thanks again for the advice on the valve lash!
Well I can't upload the video I took on my iPad but I will try and change the file type tomorrow and post it.

D2Cat · Aug 17, 2016

Might want to double check you clearances. Here's what I found. It says .008

http://johnsoncitykubota.com/Kubota Engine Specifications/Kubota Engine Specifications B5100.html

Smagner234 · Aug 17, 2016

I grabbed the dimensions from the workshop manual, I attached the photo of the page. But the top end is .0005 off of .008 so I can change them. A little extra practice. Lol
A greater clearance would yield a longer compression time, which would lessen the chance for unburnt the fuel to enter the exhaust?

Smagner234 · Aug 18, 2016

I have tried to zip the movie of the potential blow by but even clipping the video down to 2 seconds is still to large. Not really sure how to operate within the 97.7 KB range. Is there another way to upload videos? Haha I thought adjusting the valve lash was going to be hard, trying to upload a video is proving much harder.

scdeerslayer · Aug 18, 2016

Put the video on YouTube, Vimeo, or other similar video hosting service and paste the link here.

85Hokie · Aug 18, 2016

Smagner234 said:
I have tried to zip the movie of the potential blow by but even clipping the video down to 2 seconds is still to large. Not really sure how to operate within the 97.7 KB range. Is there another way to upload videos? Haha I thought adjusting the valve lash was going to be hard, trying to upload a video is proving much harder.

Uploading to Youtube is very easy and straight forward - and you can upload very large files too!

Smagner234 · Aug 18, 2016

Thanks for the advice, it was rather easy. The video is here https://youtu.be/obVUDPBkf50
Does this look like blowby?
Also should a compression test be done on the engine warm or cold?

Smagner234 · Aug 18, 2016

I did a compression check on the motor (cold) and the cylinder nearest the fan was 300psi and the other cylinder was 322psi. The manual says 398 is the low range. I'm not thinking this is a good sign.. Do you think the pressure would improve if the engine was warm? Or is this a lost cause?

Kubota B5100 smoke

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