Project Big Bore

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After building the Cub 90 sidecar and the trike I wanted to build a solo machine that I could blast around the back roads on. I didn't really document the building of my other projects and they were concieved on the fly. I'd like to keep a log of this project and record how many hours in the shed I actually put in. I have a fair idea what I want to do but nothing is set in stone. Most of my budget for this project is the engine, I had the other bikes in the shed. I've had no formal training on any of the equipment used (just books). I'm not a welder, fitter, definitely not a web designer, just a bloke in a shed experimenting and I'm learning as I go. If anyone has any queries / ideas please contact me at Hope you like the story.


sidecar trike


Step 1 : Christmas comes early. Fresh delivery of the yx 165 engine, carb, oil cooler etc.

yz165 engine


Step 2 : Get a donor frame, a 1994 Honda Cub 90

cub 90 frame raw


Step 3 : Get the frame sand blasted and primed to check for rust and holes. Frame gets the all clear.

primed frame


Problem 1: Engine won't fit. The Engine Breather pipe outlet and raised hump is hitting the frame.

engine fouling frame fouling


Problem 1 Solution: Some of my favorite tools and a bit of time. Will weld in replacement piece later.

tools of the trade frame hack


Success !!!!!

Success engine in


Donor Bike number 2. Honda NSR 80

Donor NSR 80


Step 4 : Try the front end for size

NSR Front end try out


Problem 2: NSR 80 Headstock Spindle is 20mm to short. Unlike the NSR 125 that just needs a 4mm washer.


Problem 2 Solution: Cut the Headstock spindle and machined up a 20mm insert and a 15mm diameter rod for the centre to keep everything in line.

Headstock spindle cut to pieces All the pieces ready for welding


A quick spin on the lathe to bring the weld in-line with the rest of the spindle and Bob's your uncle ready to go.

Headstock spindle on the lathe Finished headstock spindle

New Headstock Spindle Fitted


Step 5 : Mock up the back end to try and get an idea where to put the back wheel

Mock up the back end

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