I bought this bike three years ago with the intention of rebuilding it into Cafe racerish format. In pretty sad condition when the fellas next door took it off the trailer for me: Upper crankcase destroyed by an errant chain, every nut and bolt rusted away, spokes rusted away, aluminium badly oxidised, some missing bits, no compression to speak of.

Not a lot of Yamaha left on the bike now, lots of custom bits and pieces made in my workshop. I do everything myself: Anodising, painting, electrical, welding, fabrication, machining , et al.

Over the three years I've been building it I've made a seat pan, tail light, headlight brackets, aluminium battery carrier,side covers, chain guard, chain adjuster, air filters, manifolds, PMA mount, single points cam and points backing plate, remote spin on filter mount, engine brackets, cooler mount, handlebar risers, fuel distributor, brake line divider, catch can, Reed valve breather, laced the wheels, turned the hubs, modified the forms, polished lots and lots of aluminum, made two harnesses – one for lights, one for ignition, converted to VM carbs, rebuilt the engine and painted the bike. Plus lots and lots of minor stuff.

This is the finished bike. I can't ride the bike myself as I have chronic RA, which has robbed me of all strength and fused fingers, joint replacements have robbed me of dexterity. That why it took three years to build. I got the two young fellas next door to take it for it first run. Everything worked fine, they ride modern technicolour nightmares, now they want a classic.

A quick video fly around.

Adam taking it for it's first run.

https://www.youtube.com/watch?v=MaFxHRc3C-Yo

A couple of manifolds I machined up for the VM carb conversion.

The TX650 originally had BS38 carbs, these are a CV carb, similar to SUs, which I detest.. Diaphragms and other bits were junk, and I don't like CV carbs so they were junked and I bought a couple of VM34 round slides.the carbs came with manifolds, rubbers, cables, pod filters and cable splitter. The manifolds were nicely made but had elongated 8mm mounting holes, requiring 6-8mm adapters and jiggling the manifolds around to line up with the inlet tract on the cylinder hea – not on my my bike!.

On fitting, I also found the cables exiting the top of the carbs interfered with the petcocks, the only option was to tilt the carbs over at a rather serious angle. This is quite a popular conversion for this bike and that's what everyone does, tilt the carbs over. Again, not on my bike!

So I decided to machine up a couple of longer manifolds to move the carbs behind the petcocks. To make them from one piece would have required a 90mm round piece of stock, a lot of waste and a lot of turning,so, I decided to make them from two pieces and press them together. The manifold plenums are 40mm with a 34mm bore to suitt both the intake size and the mounting rubbers. The mounting flanges are 90mm wide and the plenums around 30mm longer than stock.

I made one to see how it would fit and look,it worked out well, so I made a matching one for the other side. First turning down the plenum, then shaping the flange. As the two are a press fit, I made the first 25 mm of the plenum .40 mm bigger than the the remaining length, that allowed me to press them togeer without scratching the hell out of the plenums.

Once pressed together I mounted them on the lathe and machined the face of the flange nice and flat, then turned up a couple of 6mm spiggots and pressed them into place. The spigots are to connect vacuum lines from the manometer I made for syncing the carbs.

Once done I mounted everything, spun up some brass cable nipples, shortened the cables and soldered the nipples in place. I also had to turn up a couple of fuel hose adapters as the carb intakes are 8mm, whereas the petcock outlets are 6mm. I overcame this problem with a different fuel feed methodology later, but more on that later.

I then started the bike, read the plugs, changed a few jets, connected the manometer, started the bike up again and synced the carbs. Sweet as a loolly, that's how it ran. Nice crisp throttle response.

Later on, I made up a couple of pancake filters and a fuel distributor block to overcome and neaten the jumble of fuel hoses, adapters, T pieces and elbows. More on them later.

Longer manifolds do change torque and power curves, however, more so on two strokes than four.  On four strokes, the change is minimal and a 30mm increase in length does not affect power and torque curves at all.

Edited By Tony sacc on 12/08/2023 00:34:08

Edited By Tony sacc on 12/08/2023 00:36:03