1974 XS/TX650 rebuild

**th62** · Aug 1, 2020, 05:44 PM

I bought a 74 TX650 several months ago as a long term project. I'll never be able to ride it, but I enjoy building rather than riding anyway, so it's worked out well

The bike was in terrible condition, had to ask the two young fellows next door to get the thing off the bike trailer when I got it home. Way past my physical abilities now

Every piece of steel was rusted, some of the spokes had rusted completely through, all fasteners were binned, along with seat, battery carrier and a few other rusted bits and pieces.

Aluminium was badly oxidised and damaged from rough tool use. Motor was free but not running and had sustained some damage from an errant chain: Section of the top crankcase was ripped off and the shifter drum bearing mount had also been sheared off.

The bike came with a box of spares, mostly damaged: two extra carbs, extra gauges, mags and a set of rusted out spoke wheels, ignition switches, wiring looms, old bearings and so on.

Auto advance unit was missing, centre stand was broken, quite a lot of damage.

**th62** · Aug 1, 2020, 06:25 PM

First order of business was to tear the bike apart and look at the damage. In their wisdom, the Japanese decided to build the bike so the motor had to be removed from the frame to work on it, and a heavy lump of metal this thing is. The motor can only be removed by laying the bike on tnhe right side, undoing all the mounts and jiggling the motor back and forth while trying to get the motor free.

The TX is an odd mixture of over engineering and under engineering, some good ideas and some terrible ideas, as I was to find out. OtHer damage was the drive chain, despite being way beyond it's life span, it had been left in service so both sprockets had badly hooked, teeth. The previous owner had fashioned a rough auto advance plate which was at least 90 degrees out. The motor would never have fired up anyway as compression was down around 70/90lbs. Carbs were choked up, valve seats were pitted, starter gear spring had lost all tension, cam chain was stretched so much that the motor couldn't be timed, even with a whopping .30mm points gap and both cam chain guides had lost their linings.

Other visible damage was to the upper crankcase and numerous gouges in the side covers which would have to be ground out. I located a set of second hand crankcases, so sent off for them and also sent off for a seal kit, a gasket set, two new cam chain guides, a new cam chain, an auto advance unit, some shifter drum pins, valve spring seats, some stainless allen head fasteners, new pistons, rings, gudgeons and a few other little bits and pieces. I also sent the barrel off for reboring and the head off to have the valve seats reground.

Whilst waiting for the parts to arrive, I stripped the rest of the bike down, throwing out all the fasteners, spokes, seat pan, battery carrier, spokes and a lot of other bits and pieces that were just to rusted to be re used, then set about bringing the alloy back to life, a hard dirty job!

**th62** · Aug 2, 2020, 03:29 AM

Here's some alloy bits I prettied up while waiting the parts. The hubs were mounted on my lathe for trueing and removal of casting bridges between fins, then smoother and polished. Rims were in a terrible state with lots of tyre lever damage and pitting from heavy oxidising. Tyre lever damage was ground and then rims polished. Engine side covers were the same, most of the dents and gouges I managed to remove then polished them up. Front forks weren't too bad, just badly oxidised. Alsp polished the dipstick, cam chain adjuster, breather box, tappet covers, starter motor ends.

**th62** · Aug 17, 2020, 04:09 AM

A little more work: Just put the front hub together using sealed bearings, bead blasted the disk holder and drilled a few holes in the disk. Also put the rear hub together with sealed bearings. The Teles are also together, I removed all the casting marks from the sliders and polished them again, they look 100% better without the casting marks. Unfortunately I dropped the left side slider and damaged the seal surround, bugger! I'll try the aluminium brazing rods I have and see i f I can repair it. I'm thinking of doing away with the sidecovers and either making a polished aluminium battery carrienr and making a feature of it, or I'll shorten the sidecovers at the front and attach brackets to the battery carrier for the sidecovers, that way I wont have to mak e splayed manifolds.
All one handed, had the left hand index and second finger fused and the ring and pinky got new PIP joints. Not easy with just one hand all this work, but, this Yamaha is yelling at me!

**th62** · Aug 17, 2020, 04:20 AM

Built this seatbase with cowl from 1.1mm sheet. After cutting to shape, the sides were beaten down and the rear section rolled up. A cowl was then bent to shape around the upright and welded. Front mount is a rubber covered spigot, welded to a flat plate and bolted to the nose. I then bent up a raised section to cover the tank mount and welded that in Position. The rear mounts are grommets set into the cowl into which are fitted a couple of positive stop nuts I turned up. A couple of threaded tabs were welded on the rear seat loop and the rear of the seat is bolted to them. Rubber mounted seat to guard against vibration.

**th62** · Aug 17, 2020, 04:32 AM

And the seat brackets:

**th62** · Aug 17, 2020, 04:39 AM

Side covers beaten up from 1.5mm ally, then bent and twisted to follow the lines of the upper and lower frame rails, which ere at fifferent angles. Then polished them to see what they'd look like. Mounted using grommets and positive stop ally nuts I machined up.

**th62** · Aug 28, 2020, 02:16 AM

Finished off the front hub: I drilled the disk with some lightning holes, installed new sealed bearings, polished the hub and because the left side cover that covers the disk mount holes was rusted, I fabbed a new aluminium one and polished that as well. Bought some stainless fasteners, polished them up and assembled the hub. I want to go with an electronic speedo, if I can find one, so the speedo drive on the left will probably go and I'll turn up a stainless spacer in it's place. For a bit of extra bling, I also polished the edge of the disk. Hub should look nice laced up to a polished ally rim with polished stainless spokes.