Reviving a G1900

[Hugo Habicht]

Some cosmetics

Yes, I know cosmetics should come later but I am using the tractor for cutting the lawn grass and I could not stick the steering wheel centre cover missing, so I splashed out and bought a brand new one for about 25€. And cleaned the manky steering wheel. Looks much better now, I think.



Also the cover under the dash board was held by a coach screw on one side. Really bugged me having to get a screw driver every time I wanted to take the cover off. So I bought 5 of those knob screws M6x20 for 6 quid on ebay (original is M6x15), fitted a DIN 1440 big washer over it and a soft padding cut from a cork/rubber gasket material. Love it !

 

[Hugo Habicht]

Cutting deck

The position of the cutting deck was wrong as explained by some helpful members here on the forum.

The RC48-G20 is the right deck for this tractor but the front linkage is the wrong type. It was from another deck and had been cut and welded already but was still too long.

The adjustment range on the threaded part was at it's end already. I had ordered an M20x1 die for increasing the threaded length but when I wanted to do it I noticed that 1. the thread is rolled, not cut and 2. I could not turn the die holder with the other arm of the u-shaped linkage in the way. Right.

So I simply bent both arms a bit more in a hydraulic press and now I could adjust the deck properly without the anti scalp rollers touching the ground.

Got two suitable pins for the rear wheel and machined 2 14mm pins for the front linkage. Somebody had put an M14 bolt in there. Took ages to take that off every time I wanted to take the deck off. Piece of cake now.

Looking forward to trying it out when its a bit drier

 

[Hugo Habicht]

Throttle linkage

When taking off the dashboard to check the temperature gauge I noticed the bowden cable of the throttle linkage was badly frayed.





I removed the linkage and wanted to reuse the outer part, just give it a new plastic sleeve. But when I took it off I noticed it had chafed thin in one point.



So I replaced the outer and inner part, machined two ferrules and soldered them on.



Cleaned under the dashboard, replaced the grommet, assembled everything and added washers in the u shaped parts to get rid of the play and center the wire.





The throttle lever was badly corroded.



I made a new one from stainless steel and polished it a bit. I reused the plastic handle.

 

[Hugo Habicht]

PTO lever adjustment

Despite having replaced the PTO v-belts by Mitsuboschi belts in the correct size the deck would not start properly when engaging the PTO lever. I noticed that somebody had replaced the PTO brake adjustment bolt by one that was too long and the head hit the frame and prevented full movement of the pulley idler wheel lever. I replaced it with a shorter bolt (orange arrow) and adjusted the gap to the brake lever to 3mm.



The PTO lever adjustment is the spring length inside the hooks to 90mm length when engaged (yellow arrows). The PTO lever works fine now.

And while I was at it I made a handle for the lever that had been missing.





One word about the v-belts. Since there are two in parallel they have to be bought in matched pairs. The Mitsuboshi ones that Kubota is supplying are manufactured to very low tolerances so that matching is not necessary.

 

[TheOldHokie]

PTO lever adjustment

Despite having replaced the PTO v-belts by Mitsuboschi belts in the correct size the deck would not start properly when engaging the PTO lever. I noticed that somebody had replaced the PTO brake adjustment bolt by one that was too long and the head hit the frame and prevented full movement of the pulley idler wheel lever. I replaced it with a shorter bolt (orange arrow) and adjusted the gap to the brake lever to 3mm.

View attachment 141297

The PTO lever adjustment is the spring length inside the hooks to 90mm length when engaged (yellow arrows). The PTO lever works fine now.

And while I was at it I made a handle for the lever that had been missing.

View attachment 141295

View attachment 141296

One word about the v-belts. Since there are two in parallel they have to be bought in matched pairs. The Mitsuboshi ones that Kubota is supplying are manufactured to very low tolerances so that matching is not necessary.

JFYI - improvements in v-belt manufacturing technolgy pretty much eliminated the need for belt matching years ago. For example Gates V80 manufacturing standard meets or exceeds the RMA matching standard (below) right out of the box.

Dan

 

[Hugo Habicht]

I was not idle the past few weeks, so a short update here.

Combination Box

the starter output of the combination box was faulty. I was not willing to pay 250 quid for some simple electronics. I found forum threads where people cut open the box and replaced the relais, certainly a good solution.

A few people mentioned problems with the electrics of this tractor, I guess a majority of those problems are caused by safety switches and this box.

So I wanted some extra test indicators so see what is wrong with the electrics. Hence I knit my own combination box electronics, the board is ready and the software written and tested.

I have included LEDs for all inputs and outputs that will be visible on the outside of the box. So without having to revert to pulling covers and connectors apart I will be able to see what is going wrong.

Also when trying to start and the starter not working the pre glow lamp will show a blink code of the reason the starter is not running (brake, PTO, short, open circuit). An override function will allow me to start the tractor despite errors being present (turn key three times between pre glow and ignition).

This is my test setup:



And the board itself. Relais replaced by semiconductor switches and an extra input added for external engine stop in case of major faults (temperature and oil pressure) controlled from an instrument cluster controller that I designed as well.



Here you can see the LEDs bent around the side that will be visible on the outside of the box then.



I was looking for a damaged box for the connector because I was hesitant butchering my partly working box before the replacement is fully working. But I had no success, so I will have to use my own box now.

I also worked on the instruments and have ordered some material for more repairs, I will show the results soon.

Kind regards,
Hugo

 

[Hugo Habicht]

Corrosion

although most parts were still in fairly good condition the pulleys were always rusting when the tractor was not in use and the fan belt in particular showed excessive wear due to the rough surface.

So I decided to take most galvanised (plus a few extra) parts off:



The PTO belt tensioner pulley had bearings fitted into the halves and they were then welded together. The welding spots are not evenly spaced, so after drilling them out with even angles (to avoid imbalance when assembling later with bolts) it was still tough to get the halves apart to remove the bearings. Had to straighten them and flatten the mating surface:



Cleaned all parts, sand blasted them and smoothed the surface on the lathe and with a wire brush and got everything electroplated:

 

[lugbolt]

JFYI - improvements in v-belt manufacturing technolgy pretty much eliminated the need for belt matching years ago. For example Gates V80 manufacturing standard meets or exceeds the RMA matching standard (below) right out of the box.

View attachment 141318

Dan

the matching limit of the matched OE belts is a lot tighter than .150".....

 

[Hugo Habicht]

Combination Box

The starter output on my combination box was not working, so the electronics was toast. With the potting compound there was no way I could get the electronics out in one piece so I machined a few grooves and broke out the PCB bit by bit in order to save the enclosure.





Then I cleaned everything out and separated the cable with the elusive connector.



Drilled the holes for the LEDs and soldered the cable onto my own board. I added one more cable (yellow) for an external engine shut off. An AMP connector pin was very similar to the existing ones and could be fitted.



Sticker for the status LEDs on the outside and it is ready for testing. Will not gunk it up until this is done.



More to follow....

 

[lmichael]

Combination Box

The starter output on my combination box was not working, so the electronics was toast. With the potting compound there was no way I could get the electronics out in one piece so I machined a few grooves and broke out the PCB bit by bit in order to save the enclosure.

View attachment 146709

View attachment 146710

Then I cleaned everything out and separated the cable with the elusive connector.

View attachment 146711

Drilled the holes for the LEDs and soldered the cable onto my own board. I added one more cable (yellow) for an external engine shut off. An AMP connector pin was very similar to the existing ones and could be fitted.

View attachment 146712

Sticker for the status LEDs on the outside and it is ready for testing. Will not gunk it up until this is done.

View attachment 146713

More to follow....

That is incredible work

 

[Russell King]

Curious how you knew how or what to design to replace the Kubota electronics.

 

[lugbolt]

my mom's got an 1800, 2ws. On hers the rubber upper steering bushing was pretty well worn so I took it out, measured the steering shaft and the post, and made my own on the lathe out of Delrin. It actually steers a LOT easier now. Apparently the rubber bushing was putting a good bit of drag on the shaft.

just an idea I used that I thought I'd throw out there.

 

[Hugo Habicht]

Hello Russell,

Curious how you knew how or what to design to replace the Kubota electronics.

The functions of the combination box are well described in the operators manual and the work shop manual and the wires are in the schematics:



I did some modifications to the original design though:

I think it was Lugbolt that mentioned electrical problems of this otherwise reliable tractor. When trying to get it running the first time I spent close to two hours trying to figure out why it would not start.

So I included an error blink code in the software. The pre glow light will tell you by a single letter morse code where the problem is when the starter is disabled: switches, shorted wires or open solenoids.

After the third start attempt the starter will turn, irrespectively of the safety switches, so I can use the tractor and fix the fault later.

Also the starter switch signals, the safety switch signals and the outputs are now visible as LEDs on the outside, so simply opening the bonnet (hood) will make troubleshooting very easy.

The pre glow light is a 5 second timer and 10s under 0°C or 32°F. I modified the timer to a linear approximation through 5s at 20°C and the 0°C point.

Supply voltage and inputs and outputs are protected against the typical voltage spikes in an automotive 12V net of a few hundred Volts.

I measured the stop solenoid current and starter magnet current and used 40A solid state switches (90A peak). The relais seem to give trouble after years of use.

I used modern components, not available at the time the combination box was designed, so everything is controlled by a microcontroller.

my mom's got an 1800, 2ws. On hers the rubber upper steering bushing was pretty well worn so I took it out, measured the steering shaft and the post, and made my own on the lathe out of Delrin. It actually steers a LOT easier now. Apparently the rubber bushing was putting a good bit of drag on the shaft.

just an idea I used that I thought I'd throw out there.

My steering still has about 90 degree play, I believe this is mainly the worn front axle pivot, but it all adds up. I will certainly keep that in mind when I tackle the steering system, so thank you very much for the hint with the bushing !

Kind regards,
Hugo

 

[lmichael]

Maybe you can make replacements for folks?

 

[Hugo Habicht]

Maybe you can make replacements for folks?

I suppose I could but the problem remains getting the connector and enclosure. When repairing an existing one it can happen that the enclosure breaks and then I would have a problem.

I have a search here on the forum for damaged boxes. But most people would throw those out and I only received one reply (apart from fraudsters) and the US Postal Service delivered it to the wrong address and it disappeared.

Let me test my board in my tractor for a while and see how it performs.

 

[lmichael]

Perhaps retrofit more generic harnesses and connectors. I think most anyone on these forums would have the skill lever to solder in a more generic connector without much sweat

 

[William1]

Awesome job you are doing. Kudos!

 

[Russell King]

Thanks for the reply on how you designed it.

I think you showed that you also got the instrument panels made new. Is that correct or were they just cleaned up? I recall it was included in a post about replateing small parts and hardware

 

[Hugo Habicht]

Hello Russell,

I think you showed that you also got the instrument panels made new. Is that correct or were they just cleaned up? I recall it was included in a post about replateing small parts and hardware

That is correct, I modified them a bit. Firstly I wanted to know what temperature the engine has and not just "cold", "hot". Also I wanted a tacho for the engine revs and I think oil pressure is pretty important too.



The first version did not work properly, I slipped up on the instruments, driving them with 3V. They work but the magnetic force is too low, so I modified the electronics for 12V drive. I also made the drive voltage bi-directional because the (mechanical) damping is a bit high and I think I can improve on that. Hopefully Digikey will deliver tomorrow so that I can build the new boards and test them.

Also made a little tacho sensor for the flywheel, commercially available ones I found too big. I used a Honeywell VG481V1 hall sensor that is magnetically biased. You can see the little 3x1mm Neodynium Magnet in the first picture behind the sensor before I potted everything with epoxy resin.





Nice clean signal at G1900 full revs.



Here a picture of the original instruments:



Maybe a bit over the top for a lawn mower.

Kind regards,
Hugo

 

[lmichael]

On mine for tacho I opened the alternator and traced the AC signal with my little pocket O/Scope. Once I had the proper square wave I soldered everything up. I'd LOVE to have an actual instrument panel like that though