New to me b7100 hst.. lots of issues

[bx tractorjoe]

sooo.. been looking for a cheap lawnmower, so I don't always have to use my l2501..

Found this old gal for a song.. and got them to deliver it..

Now I know why it didn't sell at the cheap price to anyone else.. but it was cheap enough and I enjoy fixing up old tractors soo..

First issue, which I did not even notice till I got the mower deck on, is the oil dummy light is on.. i pulled the valve cover cap and i can see oil squirting from the rockers so i know it has oil pressure, that and the engine runs very good with no knocks, does smoke a bit bit the hour gauge says 2156 or so.. and I'm sure its been replaced the chrome ring is to nice to be original compared to the rest of the tractor.

2nd issue, the deck, from the paint is not original, and is at least 60 inch, see pictures of the tag, after putting it back on, (what a pita!) I noticed it had been modified to fit, the 3 point also does not lift it due to the bars from the 3 point to the deck are just not right.. is all I can say.. again after putting the deck on and mowing for a bit in 95 degree weather I was done..


It also seems to run a bit hot the thermostat housing was 198 degrees after mowing for 15 or so minutes.


The oil was nasty.. i changed it, no new filter so will change it again once new filters arrive, fuel filter is also nasty..

I think the rear end axle bearings are worn.. the wheels kind of shift when you start to move just a tiny bit.. but could just be me...as it was hot.. will look into that more..

I plan to add a oil pressure gauge, I am pretty sure I have one laying around..

This should be a good project.. ot sure does mow nice and runs great even with all the issues..

Tomorrow I will dig more into it..

 

[kubotasam]

2nd issue, the deck, from the paint is not original, and is at least 60 inch, see pictures of the tag, after putting it back on, (what a pita!) I noticed it had been modified to fit, the 3 point also does not lift it due to the bars from the 3 point to the deck are just not right..

That mower is designed for a "New style" B7100. Yours is probably one of the "old style" B7100 tractors. (This is just a guess). That is why it needed to be modified to fit.

It also seems to run a bit hot the thermostat housing was 198 degrees after mowing for 15 or so minutes.

A B7100 does not have a thermostat. It also does not have a water pump. It is a thermosyphon cooling system. 198 degrees is not excessively hot.




I think the rear end axle bearings are worn.. the wheels kind of shift when you start to move just a tiny bit.. but could just be me...as it was hot.. will look into that more..

From the pictures it has the original style rear hubs. These are very prone to not clamping tight to the axle. That is probably the wobble in the rear wheels you are feeling.

Get the mechanical oil pressure gauge installed before you run it much more. If the oil pressure is actually low it is probably a plug that falls out of the front of the camshaft.

 

[bx tractorjoe]

Ahhhhh the thermosyphon makes sense.. the top of the radiator got hot extremely fast.. i should of realized that when I was looking at the *alternator* saying where is the water pump?? Doh!

Will install the oil pressure gauge tomorrow.

Should I undo the oil pressure sending unit and put it there or is there a better spot to add it?

Thanks for the reply.. very helpful

 

[85Hokie]

Older B7100 had a plug problem @ the end of the camshaft - several ways to check this, some easy - some more difficult. (Drill hole on cover - or remove cover and fix)

http://www.kubotabooks.com/AutoIndex/index.php?dir=Tractor%20Owners%20Manuals/&file=B7100HST_WSM_complete.pdf

B7100 cam plug low oil pressure and dynamo bearing replacement

The problem of the B7100 front cam oil galley plug dislodging and causing oil pressure low enough that the oil pressure light comes on, has been covered by several threads on this forum and others on the internet. The symptoms in this situation was an oil light that would come on after the oil...

www.orangetractortalks.com

Info on your model:

TractorData.com Kubota B7100HST tractor information

www.tractordata.com

yours is an 80's model - easy to tell by the 4 bolt pattern on front rims

Check your dyno for play - you will need to take belt tension off, bearings can and will go bad.
AS for the heat - get a infrared thermometer and check at top of the radiator once hot (work it hard) and check the lower neck where the lower hose connects. You should be close to 200+ at the top and something like 120-130 at bottom. You need 50 F+ difference to be in good shape. If you find too hot at bottom clean the radiator inside and out. Many ways to clean - pressure washer not a good choice.

AS for the deck being "wrong" - I have a deck on my B7100 that was shoe horned to fit - it does work and works well, just was not original to tractor.

 

[torch]

First issue, which I did not even notice till I got the mower deck on, is the oil dummy light is on.. i pulled the valve cover cap and i can see oil squirting from the rockers so i know it has oil pressure, that and the engine runs very good with no knocks, does smoke a bit bit the hour gauge says 2156 or so.

There is a common problem with these engines were a small press-fit plug in the forward end of the crankshaft falls out, causing low oil pressure at idle. There's a post on here somewhere detailing how to fix that by drilling a hole in the cover instead of disassembling the front of the engine.

Or it could just be a fault oil pressure sensor. A gauge will confirm or deny.

2nd issue, the deck, from the paint is not original, and is at least 60 inch, see pictures of the tag, after putting it back on, (what a pita!) I noticed it had been modified to fit, the 3 point also does not lift it due to the bars from the 3 point to the deck are just not right.. is all I can say.. again after putting the deck on and mowing for a bit in 95 degree weather I was done..

As noted by Kubotasam, your tractor has the 4-bolt front wheel, so it is the older design. The RC60-71B is designed for the newer version with a forward facing PTO and 6 bolt front wheel.

It also seems to run a bit hot the thermostat housing was 198 degrees after mowing for 15 or so minutes.

Make sure the radiator fins are clean and clear of debris. Make sure the radiator is topped up above the bottom of the top hose, to ensure the thermosiphon cooling system can work properly. But 198° is not too bad.

I think the rear end axle bearings are worn.. the wheels kind of shift when you start to move just a tiny bit.. but could just be me...as it was hot.. will look into that more..

Probably the hubs, where they meet the big hex axle. Kubota redesigned the hub eventually, but the original design tends to wallow out. There are a few fixes, from grinding out the slot to tighten the hubs more fully, to welding on new threaded couplings so they can be tightened on both sides. Or buy the new style hubs -- probably more than you paid for the tractor though.

 

[bx tractorjoe]

Few pictures of the temps.. one top of radiator and other the, where the thermostat usually is

 

[SDT]

sooo.. been looking for a cheap lawnmower, so I don't always have to use my l2501..

Found this old gal for a song.. and got them to deliver it..

Now I know why it didn't sell at the cheap price to anyone else.. but it was cheap enough and I enjoy fixing up old tractors soo..

First issue, which I did not even notice till I got the mower deck on, is the oil dummy light is on.. i pulled the valve cover cap and i can see oil squirting from the rockers so i know it has oil pressure, that and the engine runs very good with no knocks, does smoke a bit bit the hour gauge says 2156 or so.. and I'm sure its been replaced the chrome ring is to nice to be original compared to the rest of the tractor.

2nd issue, the deck, from the paint is not original, and is at least 60 inch, see pictures of the tag, after putting it back on, (what a pita!) I noticed it had been modified to fit, the 3 point also does not lift it due to the bars from the 3 point to the deck are just not right.. is all I can say.. again after putting the deck on and mowing for a bit in 95 degree weather I was done..


It also seems to run a bit hot the thermostat housing was 198 degrees after mowing for 15 or so minutes.


The oil was nasty.. i changed it, no new filter so will change it again once new filters arrive, fuel filter is also nasty..

I think the rear end axle bearings are worn.. the wheels kind of shift when you start to move just a tiny bit.. but could just be me...as it was hot.. will look into that more..

I plan to add a oil pressure gauge, I am pretty sure I have one laying around..

This should be a good project.. ot sure does mow nice and runs great even with all the issues..

Tomorrow I will dig more into it..

Tighten up the wheel clamps and replace the oil pressure sending unit.

Did not read other posts.

SDT

 

[D2Cat]

I read this post and had to double check the date....85Hokie is back! Stick around man, I been missing you.

 

[bx tractorjoe]

Ok well my eyes must of been messing with me.. the oil dummy light is not hooked to the dummy light.. and does not come on at anytime.. going to see if its getting power.

Rigged up a oil pressure gauge.. has very good oil pressure when cold.. going to five the engine a good pressure wash then mess with the deck lift mechanism

 

[bx tractorjoe]

Ok well this is a tough old girl.. ran it in 95 degree heat and cut about an acre and a half and after mowing the oil pressure was still at 35 40 pounds..

Oil temp at 174, bottom radiator hose at 140 top at 190 at maybe 1200 rpm.. when I increased the rpm to maybe 2500 it quickly dropped to 170 degrees at the top of the radiator..

I'm pretty happy with her..

Also adjusted the deck lifting bars and now it will pick the deck off the ground.

The wheel clunk I was seeing is indeed what you guys said it was..

Also need to get a new dipstick as the rubber part moves and it also leaks from being dried out.

I also welded the seat brackets back as one was broke and one was about to break.

 

[Kenonf]

Ok well this is a tough old girl.. ran it in 95 degree heat and cut about an acre and a half and after mowing the oil pressure was still at 35 40 pounds..

Oil temp at 174, bottom radiator hose at 140 top at 190 at maybe 1200 rpm.. when I increased the rpm to maybe 2500 it quickly dropped to 170 degrees at the top of the radiator..

I'm pretty happy with her..

Also adjusted the deck lifting bars and now it will pick the deck off the ground.

The wheel clunk I was seeing is indeed what you guys said it was..

Also need to get a new dipstick as the rubber part moves and it also leaks from being dried out.

I also welded the seat brackets back as one was broke and one was about to break.

 

[Kenonf]

I added another piece of flatbar to my broken seat mount, while welding, but then I am 6'6" and 260lbs.

If you go back to the dummy light on the oil pressure, don't waste money on after market, get a Kubota unit, speaking from experience....

Replace the dust cap on your air filter too, it will help keep filter cleaner.

I cleaned the dipstick with acetone, and put a drop of superglue on the metal rod, and slid rubber back into position, still holding.

The rear hubs will really wear into the shaft, if you keep it, get the newer clamping hubs, it is a bit difficult to have to slide hub back away from the mower and three point hitch, where it will inevitably walk itself after breaking the pin/bolt in the hub.

HST not returning to neutral is a common issue too, lots of threads on fixing that here.

I added a coolant tank to one of mine, and them put the whistle on the overflow hose

Glad to see people are still acquiring, using B7100s, don't feel so out of date now, liked mine so much I acquired a second to just pull trailers when the other has stuff on 3 point hitch, or just busy(my two boys).

 

[flynavy]

There is a common problem with these engines were a small press-fit plug in the forward end of the crankshaft falls out, causing low oil pressure at idle. There's a post on here somewhere detailing how to fix that by drilling a hole in the cover instead of disassembling the front of the engine.

Or it could just be a fault oil pressure sensor. A gauge will confirm or deny.



As noted by Kubotasam, your tractor has the 4-bolt front wheel, so it is the older design. The RC60-71B is designed for the newer version with a forward facing PTO and 6 bolt front wheel.



Make sure the radiator fins are clean and clear of debris. Make sure the radiator is topped up above the bottom of the top hose, to ensure the thermosiphon cooling system can work properly. But 198° is not too bad.



Probably the hubs, where they meet the big hex axle. Kubota redesigned the hub eventually, but the original design tends to wallow out. There are a few fixes, from grinding out the slot to tighten the hubs more fully, to welding on new threaded couplings so they can be tightened on both sides. Or buy the new style hubs -- probably more than you paid for the tractor though.

Addressing the low oil pressure...check out this youtube video, this guy showed exactly how to fix it! He says in the video that he got from a Kubota Service Bulletin. The video is long but worth the view just for the information he gives. Check it out

 

[torch]

That's a old 2-cylinder L series in the video, so many details will differ from the B7100, but it clearly shows the camshaft plug issue common to both.