So, it’s all been quiet recently on the website and social media pages as attention has been diverted to the diesel bike build and hitting the green lanes on my new Triumph Explorer.

To say it’s been a challenge over the last couple of months would be the understatement of the year, how I have persevered and now might see the faint glimmer of light at the end of a very long and dark tunnel.

I eventually got a used Kubota engine in the workshop, which needed a full strip down and reassemble with new pistons, piston rings, head gasket etc as well as inspection and passing of the crank and bearings etc. I had wasted lots of time and money on another Kubota engine, that had been damaged in transit and was useless to me, hence the big delay.

Once the engine was all put back together, I started to look at how I might connect the engine to the BMW K75 gearbox I had also recently acquired and had cleaned up. 

The current plan was also to source a BMW K75 or K100 donor bike in order to make the final drive arrangement work better…and go about trying to sell the VW TDi engine and GL1000 Goldwing rolling chassis to help fund everything. Well, suffice to say that plan failed miserably as the summer prices inflation affected the BMW starting prices and I got very little interest in the engine and chassis sales…oh well…onwards!

I knew that the next big puzzle would be how to not only connect the gearbox to the engine but also how I could introduce a clutch arrangement into the set up and for it to work properly.
Luckily I had bought a used BMW K75 engine and gearbox as a complete unit, so I was able to scavenge the clutch unit from that and once I had chopped off the back splined shaft (that would have fit into the BMW engine crank, I was then able to fashion an adapter plate out of 5mm sheet steel.

Fortunately the Kubota flywheel already had five stud bores which to attach the adapter plate…and after lots of measuring, cutting paper templates, metal grinding and drilling, I was able to attach the clutch to the flywheel with some spacers and it did not look too out of place either…albeit rather crude in appearance.





So after many hours deliberating whether this was actually going to work or not and multiple trips to the ironmongers to buy fixings and grinding & cutting discs, I was now in a position to start on the next puzzle…How to attach the gearbox and how to ensure it would line up correctly?

My attention then turned back to the engine and I noted that I was missing the bell housing that would cover the starter ring and flywheel. I was able to connect the gearbox to the clutch via the splined shaft and internal push rod assembly and had it all lined up and supported with bits of wood. So whilst I tried to source a bell housing from Ebay for ‘cheap cheap’, it dawned on me that I might be able to fashion another adapter plate and could rape the BMW engine for its bell housing which would connect directly to the gearbox.

So once again, the paper and crayons came out to make a template for the adapter plate which would have the same hole pattern as the engine starter ring back plate. I had already sourced some 4mm aluminium square plate sheets, so set about cutting out the centre part to allow clearance over the clutch plates and drilling holes to match the template.

After another trip to the ironmongers for more fixings and cuttings discs…and lots of fettling, I eventually managed to fix the gearbox adapter plate over the clutch, so all that was left to do was to hack away at the BMW engine bell housing until I could mate it to the gearbox and the other side of the adapter plate, whilst ensuring that the gearbox was lined up and was the correct spacing from the engine and clutch…Yes…lots of measuring and test fitting did take place.
After two weeks of cutting, drilling, grinding and and bashing on metal, I finally was able to fashion a rudimentary adapter plate that connected the gearbox to the engine utilising a single sheet of aluminium and numerous home made studs.

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The set up was complete, albeit rather crude and unlikely to win a beauty contests…but something was nagging at me that it just wasn’t sturdy enough.

So out came the ruler, grinder and drill bits again so that I could double up on the aluminium sheet and more fixings to bolt it all together. A bit more grinding of the engine bell housing on the adapter plate side to narrow the gap and make it more flush and more fixing points made.

Check out the next post to see the next version of the adapter plate and gearbox setup and whilst the BMW K75 donor bike is still being sourced, I have started to think about the Goldwing chassis again as a realistic option. It could just work, but will take a lot of metal work and frame modification to see it through.