Restoration of a 1974 SX-175
Bike runs good but still smokes too much from the exhaust when the engine is cold. Also some oil / gasoline mix comes out of the exhaust.
I checked the carb and wrote down the jet settings in case I have the experiment a bit there:
Starting jet: 70
Main jet: 100
Low speed jet: 55
I am currently writing an article for a “classic motorcycle” magazine in Germany about the SX-175. Today I took the bike for a little spin and a photoshooting for that article.
The bike is finally complete and was running for the first time a few days ago. The carb needs some adjustments, but overall it looks good.
Yeah, I am almost there. Only the accelerator cable and the gas line are missing and then it’s done.
A litte life sign. Haven’t done much work on the bike lately but I am progressing slowly with the wireing harness.
This time I didn’t split the crankcase as I tested the engine and it was running fine and strong. The previous owner also had a new piston and rings made for the bike.
As you can see in the first few pictures there had been a few dents and even holes in the exhaust manifold, also some smaller dents in the muffler. As the 1974 model has a different exhaust as the later models I wanted to keep this exhaust for my restoration. In the first step the exhaust was sandblasted and cleaned. After that the dent in the manifold was cut out and the exhaust was welded by a professional welder. I then grinded everything back to it’s original shape. As the welded spot had a very smooth surface compared to the rest of the abrasive or rough material I had to adjust this part to blend in again. In the end I sprayed it to it’s original black color again. The exhaust grill was already rechromed and ready to mount as well as my SX-175 emblem which was laser cut and custom built by myself.
The wiring harness was incomplete and in bad shape. It was also altered by the previous owner. I decided to make a complete new wiring harness from scratch.
As first step I colorized the original wiring diagram which helped me a lot for building a complete new wiring harness. This also meant buying a lot of cables in different colors.
Kickshaft and seal (20-30-7) needed a replacement. The clutch cover is ready for beeing remounted to the crankcase. Luckily I had a brand new kickshaft at home.
This is my freshly dry ice cleaned cylinder together with the glass bead blasted cylinder head. Before and after pictures for comparison.
I heared a lot of people saying that dry-ice-cleaning ist by far the best method.I personally don’t see big differences to glass-bead-cleaning and it is also more expensive.
There were some pieces broken off the crankcase. One large piece was missing below the flywheel. I have no idea how this happend. Maybe a previous owner hit a stone while beeing off road with the bike? Another large piece seemed to be knocked out by loose chain. I bought a used left crankcase-half and cut out pieces to fit in as “spare parts”. I didn’t intend to replace the whole crankcase as I wanted to keep my matching frame & engine Vehicle Identifican Number (VIN). So, I went to a welder and asked him to weld my cut-out-pieces in my old crankcase. I asked them for laser-welding, but as you can see my request was totally ignored. This meant a lot of work for me as now there was a whole lot of material that needed to be grinded of. This took me a lot of time and two more rounds of adding material to get the surfaces smooth to blend in with te rest of the crankcase nicely.
Overhauling the 27mm VHB Dell’Orto carb was a routine work as I have done many times on my other Aermacchi bikes. Spare parts are still available and so I replaced most inner parts with new stuff. Those parts I reused as well as the housing were cleaned in an ultrasonic bath.
Here you can see my selfmade decals mounted to my bike. It was a lot of work to get them designed correctly but they are perfect reproductions to fit exactly the 1974 SX-175 gas tank.
Okay, at this point we had a good rolling chassis. All the parts are there and some are already restored like the frame, wheels and front fork.
>>Brake check?<<
>>Nope, doesn’t work!<<
Overhaul of the front wheel hub is complete. Everything cleaned and both bearings replaced with new ones (Size 6202). I also replaced the brake shoes with a brand new set as well as the springs.
The pleasing result of the aluminium polishing and the glass-bead-blasted cylinder head.
Thats the aluminium parts I am sending out for glossy polishing. The cylinder head will be glass bead blasted to look like factory new.
Here you can see the completly redone rear wheel. EVERYTHING was replaced with new or NOS parts: Hub, bearings, seals, chain adjusters, sproket, spokes, rim, tube, brakes, springs, tube holders and the tire itself. The last pictures shows my current progress and my design for reproduction gas tank decals for a 1974 model. Original decals are not available and the reproductions sold are not good enough in my opinion for a perfect restoration. You can also see that I was able to get a vented right side cover which was only mounted to the first models sold and then replaced by a different style.
The completely redone seat with the original seat pattern and Harley-Davidson lettering in the rear and a powder coated seat pan.
One of the best moments when restoring an old bike is to get the rechromed parts back, but also one of the most expensive moments. 🙂
The second picture shows some NOS parts I gathered for my project.
New brakes and springs for the the rear wheel.
I bought some NOS parts from my favorite parts supplier “Carl” who also found me a pair of perfect Sebac five-way-adjustable rear shocks. Those are really hard to find thes days. He also had a NOS rear fender for me.
Just some parts before the restoration.
As the aluminium rear hub was broken I ordered a NOS replacement part. I also gathered two sets of brand new brake shoes and springs.
A new air filter and seal as replacement for the old used ones. I also bought a new headlamp housing and I will replace the headlamp with a modern H4 to get some light out of it. I will also replace the ignition key and rubber boot as well as Speedometer and tachometer with NOS ones.
Parts back are back from powder coating and the meanwhile overhauled front forks are freshly polished and fitted with new seals (32-42-7), reflectors, sliders and new rubber dust covers.
A picture of the frame, rear swingaarm and some other parts before I send them out for powder coating.
I have disassembled the front fork so I can overhaul it. The sliders will be replaced with NOS parts.
Marzocchi:
32mm;
Fork seals: 32-42-7 – two each side;
The bike is now completely dissassembled and the restoration process can beginn.
The previous owner of the bike did cut off the turn signal stuts so I had to remanufacture them and have them welded to the frame.
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