1973 Yamaha TX650 Project

00:30
02/25/2020


How it all started:

The first thing I did after graduating High School in '62 was what I HAD to do.... work on motorcycles. I managed to get a job at Ted Evans Triumph and Ariel in Venice, California, and had a great time. For a while, at least. After a few months, I got a bit tired of always having dirt under my fingernails, so I wandered off to other pursuits. The Triumph twins, however, had made an impression. Bounce forward 45 years, and I was playing around with a bunch of different bikes, and I still hadn't had my vertical twin.

Triumph, the old company, had long since gone the way of the Dodo Bird, and the new company just wasn't the same. I own a 2001 Tiger, and it's more bike that I really need, so I started collecting oldies but goodies. I came across this Yamaha in Stockton, and bought it for $300.00, which seemed like a fair price at the time. It sat in the garage for a couple of years, before I finally got around to working on it seriously. These pages will document that adventure.

Left Front View

Rear View

Right Front View

Obvious from the pictures: There's no headlight. There's no front brakes. There's no passenger foot pegs, or mounts for same. The mounts were a welded on item at the factory. I had them in a box of parts that came with the bike. That was only a hint of what was to come. Every possible mount had been removed from the frame, including the chain guard mount, the seat mounts, and I don't know what else. There was a pair of flat mounts welded to the frame for mounting a solo seat, but that seat wasn't included in the package.

Not so obvious: There should be a hanger mount of some kind on the muffler. It had been cut off.

The rear wheel was steel, the front aluminum, and only somewhat later did I discover that the space between the front forks was considerably more than the width of the front hub. Some previous owner's response to that situation was to pinch the forks together, pidgeon-toe'd.

The front forks couldn't move.

The front instrument panel originally included a spedometer, an ignition switch, and a tachometer. The mount had been butchered, and only the tach was mounted. The switch and key were in the parts box, the spedo wasn't.

I'm going to get well acquainted with Mike's XS



The front fork challenge:


Three pictures follow. The first is of the tripple tee. The second is the lower fork legs. The third is a (rough) drawing of the dimensions involved. I don't have a caliper long enough to accurately measure the width of the hub, or the space between the fork bosses at the bottom of the fork, so those are the "rough" part.

Tripple Tree

Lower Fork

Dimensions Drawing

The inner fork tubes are 150 mm apart, inside. If my math is correct, that makes them 184 mm center-to-center, and 218 mm overall width. The width between the fork bosses at the bottom is 6 9/16" (166.62 mm), while the width of the front hub is 5 7/8" (149.22 mm). In other words, it don't fit together. For what it's worth, the axle seems the correct dimension for the hub, and the diameters are correct for the fork bottom bosses. It's only the width that is a problem.

Guesses:
1. This is not the correct tripple tee/front fork setup.
2. This bike was originally steel wheels (probnably true), and steel wheels have a wider hub than do alloy wheels. I have a hard time believing that, but possible.

According to Michael at 650 Central, the 150 mm dimension between the tubes is correct, so I'm inclined to think the hub is the issue, not the forks/tripple tee.

I tried to replace the front end with one from an '81, but the steering stem on the '81 is about 1/2 inch longer, so it doesn't fit the frame neck. Some weeks have seven Mondays in them!



Additional info:


Here's pictures of two wheels. The first is the one that came with the bike, alloy, single disk. The second one is from a '79 XS (I bought both wheels from a '79, dual disk front, and alloy rim, drum brake rear). The hubs appear to be identical, except the '73 has a chrome cover in place of the extra disk on the '79. The hub width is the same, within my ability to measure them. As the previous owner had hacked up the instrument cluster, I also obtained the mounting hardware from the '79. The dimensions are totally different, aside from the presence of the instrument lights in the center of the console, vs. in the guages. The gauge hole dimensions are different, as are the mounting holes

Wheel from the bike

1979 dual disk wheel

Color me stupid!


I tried my best to find out about the spacing, and if I had the correct front forks, but to no avail. I purchased a complete front end off an '81, only to discover that the stem on the tripple tree was longer on that one, so It wouldn't work. I had the front end completely apart at that time, and couldn't find a set of forks for a '73, so I thought I'd put it all back together and build a set of spacers so I could live with what I had, at least for the time being.

Well, I put the front end back together, and the wheels fit! No way! Can't be!

It wasn't possible. It finally occured to me that the forks were bent, and I had just accidentally put them back in so the rotation made it seem as if the width was correct. I took it back apart, took the fork pieces to the Motorcycle Frame Straightening Man, and in a couple of weeks, I had a straight set of forks.

While I was dis-assembling the forks, I finally ran into a dampner rod that I couldn't get out, so I made a tool to hold it while I un-screwed the bolt from the bottom end.

I started with a steel rod, about 3/4" diameter. I drilled a hole through it, got out the cutting wheel, and made a slot. The rod is on the left, and the dampner rod with the oval shapped head is on the right.

Part 2 - Fixing the broken bits

 


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Revision: 01.0     Email Doug     09/08/2007