1974 XS/TX650 rebuild

[th62]

Yesterday I made another twin lobe points cam. The original I made worked fine, but was slightly out, so I did a little more filing, too much ask it turned out, a few swipes with a file took it past the midway point on the backing plate adjustment.. I've made a few of these points cam, very difficult to get accurate, one swipe of the file can ruin a hole days work. But this one I got spot on for both cylinders. Today, I made a clamp to hold a bit of felt to lube the cam, very small exacting work. After all that I polished the cam and backing plate, just because something isn't seen doesn'mean it shouldn't be shiny. I once polished the rocker arms on a Bonny.

[olderdan]

I did the same polished rocker arms on my T100SS just for the pleasure of knowing its in there looking good.

[hemmjo]

Polishing internal parts is much more than just visual obsession. It has profound effect on performance. When done properly it also makes parts stronger. This may be counter intuitive, since material is removed during the process. However, by removing surface imperfections, you also remove places where fatigue cracks can begin to form.

For reference, try to break a piece of glass, then scratch one just like it and notice how much easier it is to break. It also enhances oil flow. There is some research however to indicate that polished intake runners in carbureted engines can cause fuel to condense rather the stay atomized in the intake stream. I do not have enough information to say ya or nay on that..

Many connecting rods and other parts in modern high performance and race engines are aluminum, or titanium, forged or CNC machined from a forged billet, then polished in Giant Finishing Machines. Back in the day, us poor unfunded hot rodders would polish stock rods and other parts by hand to make them stronger.

We even polished entire engine blocks, cylinder head, rocker arm surfaces, etc to allow oil to flow more freely back into the oil pan. At high RPM it is possible to pump all of the oil out of the pan because it pumps out faster than it can drain back down.

Giant Finishing, has a whole series of videos on youtube about vibratory finishing. If you are interested, put Giant Finishing Episodes in the YouTube search bar. Then click VIEW ALL EPISODES. This will show you the whole list.

Two videos specifically related to this topic are;

66 Giant Finishing - How To - Finish Connecting Rods - Part 1 and 67 Giant Finishing - How To - Finish Connecting Rods - Part 2

There are many other videos of cylinder heads, crankshafts, valves, headers, etc.

After a while they get a bit repetitive, but at least for the 66 and 67, be sure you have the sound turned on and watch at normal speed. I won't tell you why, you can be surprised. Being pleased or not, will depend on your age

[Saltfever]

It's not stronger (you are not changing the composition of the material) but you are increasing cyclic fatigue life.

[nova_robotics]

It's not stronger (you are not changing the composition of the material) but you are increasing cyclic fatigue life.

Ultimate tensile strength increases as well. Probably doesn't help when a material is in compression, but tension, shear and bending can be improved. Surface imperfections cause stress concentrations when materials are mechanically loaded, which act as a "nucleation point" for failure.

...but if you're running that close to the limit you probably have other issues. I have never polished something with the intention of making it stronger. Just make a better part.

[th62]

The morons have invaded.

[th62]

Give it a rest morons, I think you have stroked your egos enough.

[th62]

That's three more added to the idiot list. I really don't understand these morons that need to stroke their egos all the time, then move onto stroking something else.
For the morons, who obviously think they know something nobody else does, polishing conrods for example does not increase strength it simply removes defects from the surface thus preventing cracks starting. Shot peening does pretty much the same thing. Polishing rocker arms on the other hand is purely for aesthetics. Itnalso does notndecreasebstrength. By polishing the metal you are simply removing the high spots thus levelling the surface. The high spot have no value in terms of strength.

Don't bother replying and stroking yourselves any further, I have added you to the idiot list, ie, the ignore list.

[th62]

More on the hydraulic clutch conversion. A total fup!

This is a new 20mm clutch slave cylinder I machined up for my 74 TX650 to replace the 25mm slave I made. The 25mm slave didn't work as the piston only had around 1mm movement using the 9.5mm master I bought.

The new 20mm slave was machined up from piece of 6061, the piston is 304 stainless and the seal used is from from a hydraulic ram. Instead of using a circlip to retain the seal, I machined a cover to both keep the seal in place and also to act as a dust seal.

To fit the slave I bored out the actuator hole in the clutch cover from 26 to 29mm and drilled the M5 threaded mounting holes out to 6mm and bored them to take allen heads.

The 9.5mm master I bought for it was advertised as using mineral oil, which suited me as I dislike using brake fluid. Unfortunately, the ad was wrong, I used mineral oil and the piston seals swelled up and jammed the piston. WhenI finally managed to get the piston out, one of the seals was damaged, rendering the master useless.

Replacement seals are unavailable for this master, so I decided to retain the screw actuator. This engails returning the clutch cover to original. To do this I turned up a couple of stainless 6mm T nuts and threaded them M5 and pressed them into position. I then turned up a Delrin spacing ring for a press fit around the screw actuator.

It all works as it should now with no obvious signs of the modifications I made. And now I have a 20mm clutch slave sitting in my useless parts bin.

So, all for nought... I'm now back to the original cable actuated clutch.

[th62]