Hi everyone,
Here is another update on my current project of the engine upgrade on my B7100.
This project of mine started out just as an idea to be honest, my 7100 was work pretty well but did need some attention in several areas, the engine being the first port of call, in reality, it has turned out to be far more than just that, a heck of a lot more.
As already mentioned at the start of this thread I was planning on replacing my tired D750 engine and retro fitting a D850 engine into the 7100 instead, details of which I have been updating this thread when I could.
What I have now ended up with is a completely new project, don’t ask how I managed to get so far entangled in this , I really don’t know, the whole project just seemed to grow and before I could say job done, the whole tractor was a large pile of bits on the workshop floor.
Anyway, you should have already got a good idea of what I have done so far on the engine front, its pretty well rebuilt which on the overhauling of service parts was pretty well text book , but there were a few more issues that I had to address to be honest which I forgot to mention earlier in the thread that most certainly were not text book.
After I had overhauled the head etc and was about to refit it when 3 problems came to light, and not all at once, problems that were not obvious until the fitting of the head.
Anyone could be forgiven, that after looking at the technical specs sheets etc for the Kubota 70mm series engines (D650/750/850/950 )and then assume that all share basic layout features, with the ancillary parts being the differing factor depending on the engines application, not so, its not just the ancillary parts that are a factor when considering a retro fitting between the group of engines.
Here is a classic example on my project, my D750 engine head/block uses M8 studs & bolts, the D850 I have uses M9 bolts only, not a major problem as the later B7100 with the 750 engine were fitted with M9 studs &bolts.
The problem arises now that because of the way the generator is mounted to the engine, it mounts via a 3 piece bracket just above and in front of the injector pump, so then, the m9 bolt will not work, it has to be stud as the bracket mounts on top of it with another nut to secure the bracket, and a long stud for that matter.
I had to order the stud from my dealer, and when I recieved it the part number was correct but it was still to short, another 24hrs later and a lot of phone calls to Kubota UK the correct part and part number was located, it was a modified part to later engines, but not clearly listed on parts sheets.
On the subject of the pre-combustion chambers, they just knock out with a drift via the injector hole, to refit, just line them up and knock them back in with a suitable drift , done.
So that solved that issue, and then the next one.
This is also a problem that only effects the type of engine I am using and revolves around that pesky generator mounting position.
The cooling system bypass link from the water pump & thermostat housing is different, the outlet tubes on the 750 I have are a screw in fitment and are angled so as to move the rubber bypass hose back away from the belt, on the 850 they are straight and a push in fit, so you cant even swap over the outlets, luckily I had a nearly new
water pump which was the correct item otherwise I would have needed to buy a complete new water pump.
Right that’s that issue sorted.
And onto the next , also a cooling based problem.
On the front of the D750 cyl head the thermostat housing assembly is held on to the cylinder head by the use of 6 bolts(5 short 1 long), on the 850 I have its different.
There are 5 short bolts, same as before but the the long bolt has been replaced by a stud, and due to the extra length of the tread now protruding from the face of the nut the cylinder will not fit correctly due to the contact with the belt tensioning assembly ( also a different item).
So , out with the stud, luckily the long original fitment bolt does screw in fine.
It can clearly be seen that just one differing item on one of these engine can have such a larger effect on so many other parts.
To be honest, if it was not for the fact that I had enough donor parts to start with , I may have aborted this project on the basis of overall cost.
So in summary on the engine part of the project, was it worth it, yes.
Cost wise the engine has totalled £300 and its ready to fit now, from a time point of view, its has taken a couple of weeks to complete , working during the weekend and some evenings, so not to bad.
What I would say to anyone thinking about doing the same, make sure you get the right lump from the start, it makes things so much easier.
I suspect this sort of project has been performed so many guys with no hassles at all, its not difficult, but you need the right basis to start with.
My was close, not ideal, but close enough as it came at the right price and was of low usage etc, also if you want to swap parts over, make sure that they will swap over without giving added problem like I had.
I have added pics of the above also.
I am going to rename this thread “ don’t try this unless you are totally bonkers”, well I’m going to start a new thread as the whole tractor is in parts and I’m rebuilding the rest from the ground up with the addition of some nice extra parts here and there, but that’s a new thread and this was just about the engine.
The next part of the revised project is underway.
Well hope that wasn’t to long…….and that it helps someone out in the future.
rob
