bchrismer's '72 Z50

I changed the name of the thread to reflect the progress of getting my '72 back in working order.

After looking through the "Show me your z50s" thread, my initial dreams were to do extended fork legs and a 10cm extended swingarm. Since it has always been stored indoors, the paint and chrome is still all in rather amazing shape for a 51 year old bike.

I don't want to stray too far from the original look, so I pulled the trigger on a Tanaka Trading 5cm steel swingarm. This should allow for a better centering of the rear wheel in the arc of the fender. I figure a set of shock extensions should get me back in the right ballpark for the added length of the extended swingarm until I can get a good measurement for some replacement shocks.

I am assuming that swapping the fork springs to a set of the heavy duty springs will take some of the sag out of the front to help level it back out.

Looks like the plans will go like this:

Replace the missing tail lamp lens, grip, and handlebar knob set.
New swingarm, chain, and HD fork springs and Derlin bushings for the first round of mods.
88cc top end and high volume oil pump at a later date.

Not an exciting "build" but it's mine and will be fun entertainment for this old fart.

So, being the fool who soon departs with his money, as the proverb says, here's my two "new to me" swingarms. The top one was an original '76 that I bought on the Ebay with the intention of having a buddy add some extension to it. Then, after considering the cost of sandblasting and powdercoating, decided it was just a better solution to buck up and buy the Tanaka Trading black 5cm extended swingarm. I figure I saved myself more money doing it this way than the cost of his time and the powder coating costs combined, plus it will allow me to run my stock chain guard and it came with the extended rear brake rod.

Now I just need to get a factory sticker for the right side of the swingarm to help pull off the "stock" appearance.

(Oh...and yes, the photo location is in the bed of the 1940 Ford Stake truck shown above, that still has all the factory wood for the bed floor and stake sides)

NERD ALERT

Just a fair warning, my brain gets obsessed with the "planning" part of projects. So much so that I usually start out with a spreadsheet and instead of just keeping track of where my money went, it's trying to figure out math problems to get the results that I have pictured in my brain.

An example of this obsessive behavior was choosing a manual transmission for my '40 Ford coupe, based on the rear end gear ratios, RPMs at take off and shift points, and the resulting RPM points after the shift has been made, just so I know what to expect when it's time to drive them. Turns out sometimes that works perfectly, and in the case of my '40 Ford panel truck, it resulted in me needing to change the rear gear ratios to get the RPMs in a range that shifting from 3rd to 4th didn't drop me below the power band of the 85HP flathead.

Today's mathing problem involved a z50 that's in KCMO, me in Springfield, a measurement from a stock and a 5cm extended swingarm, and an educated guess of the stock shock length of 280mm. (I HATED 8th grade geometry, and don't remember much, so I am thankful for online calculator tools for stuff like this.)

I actually kind of already knew the answer from having read a BUNCH of threads on the topic, so the answer is 12 to 12 1/2" or in the neighborhood of 305-315mm, but I had to solve the problem for myself.

Keeping the angle from the swingarm pivot to upper shock mount the same, results in needing the longer shock. It also will result in a slightly raised back end of the bike without any rider weight on it, which I am definitely a fan of since I will need that room since I am now a long time member of the "Tenth of a ton" club.

By using the protractor on the image of my z50 sitting in my driveway, I was able to calculate the approximate angle from the axle to the swingarm pivot, and up to the shock mount.



Using the known length of 280mm shock, and the 9" between the shock mount and pivot bushing center, and the 73degree angle of the swingarm to pivot and upper shock mount, it gave me a measurement for the distance between the upper shock mount to the pivot bolt.



I was able to change the formula to use the extended length of the new swingarm, and it gave me a measurement of 311.



The result of this? Well, I chose to spend some Amazon credits on a pair of 1.5" shock extensions to see how my maths prove out before dropping money on the final shocks that will appropriately support my lard butt. LOL

(Oh, and just for funzies, the bottom of the triangle should be pointed down at about a 21 degree angle to make it look right.)

Latest text from Dan:

Back on the operating table, it shifts all three gears with the clutch basket off, so problem must be in clutch area. The shift actuator has separated and bent, so does the clutch kit you're looking at have the actuator parts with it?

The clutch plate ring has got some wear on it from the rollers.
That's all I've found so far!
<<>>

So, I called him up and we talked through the clutch issues. He did say that he fired it up and rode it around on his second attempt. He said the first attempt it got away from him and left him sitting on the driveway. LOL

With all the wear on the clutch internals, I wound up placing an order with TBParts for a new HD clutch, the high volume oil pump, and the 88cc + carb kit, and an order with CHP to get replacement parts for the actuating stuff, and a new set of grips to replace the missing one and make sure they both match.

I asked him if he wanted to just box everything up and bring it back and I could do the rest, and he offered to let me just ship everything to him and he'd have fun doing it.

In hind sight, I think I probably should have added larger front sprocket, but failed to do so. It would be a great time to do that since I have the +5cm swingarm and will have to replace the chain.