The first walk around after having the bike at home is still good. Almost everything is there. Nothing seems to be altered or incompetent repaird. An emblem on the dampener knob is missing, the tail light ist broken, but no unexpected surprise so far. A decal at the ront and rear fender says “Officina Riparazoni Auto Moto Aermacchi Harley-Davidson Cycles F.LLI DELFINO via Carlo Ma?? Tel. 62906, Alessandria”.
Totally unexpected I have a new Aermacchi restoration project! Accidentally I saw a sales ad for an Aermacchi Chimera which went online just five minutes before I discoverd it and the bike was also located in Germany. This alone does not happen very often, but the price was good as well. I called the seller then everything happend very quickly. Two days later I was driving 500 kilometers north through Germany to get the bike and instantly another 500 kilometers back with the Chimera on the trailer.
What I do know so far: The bike was running until 1986 in Italy. It has 31.000 kilometers on the odometer and was imported to Germany in 1989. Obivsously it was kept in private motorcycle collection since then.
This is a 250cc Chimera. The exaxt model year is unclear at the moment The decals suggest that it is a model between May 1960 and 1963 as it already reads “Aermacchi Harley-Davidson. According to A.R.S.I.M.A the bike is in an overall original and complete condition and the grey color was experimental by factroy to show dealers new color options”. I am very happy about the condition, even both steering lock keys are there. I do not know if the engine might work, but the bike shifts and the piston is free. Engine and frame VIN are original and matching. I got an import certificate with the bike and a bill of sale.
What makes the Chimera special?
The Chimera the ancestor of all the Aermacchi four-stroke bikes. The engine was developed especially for the Chimera by engineer Alfredo Bianchi. This new OHV motor with almost horizontal Cylinder was also used in later Aermacchi 175cc and 250cc models like Ala Rossa and Ala Verde and it was also the Basis for some sucessful Aermacchi racing bikes like the Ala d’Oro. The engine was later redeveloped as 350cc motor and in 1973 it got equipped with an electric-starter-motor until model year 1974 when AMF Harley-Davidson decided to stop the production of the italian four-stroke bikes in 1973.
Designer Mario Revelli di Beaumont was contracted in 1956 by Aermacchi to design this new four-stroke motorcycle. He was an experienced designer and also a motorcycle race driver who was already involved in designing some famous Fiat cars. In the 1930 he also worked for Pininfarina. Revelli got free hands designing the Chimera. He decided for the futuristic enclosed engine housing in a “turbine desgin” and a uncommen gas tank which is one piece together with the rear fender to show Aermacchis ancestry as aircraft maker. The bike was unveiled at the milan motorcycle fair in Dezember 1956.
The Chimera is also one of the first motorcycles in the world where allen screws had been used. Parts of the body are aluminum cast and fit very precisely to avoid vibration noises. The engine side-covers themselves are part of the Chimera line and and made to fit perfectly into the design. The bike is as well equipped with a telescopic Upside-Down front fork and a monoshock rear suspension to not disturb the elegant linie of the bike.
Beside all the effort and money that was put into the project the Chimera didn’t sell well. Aermacchi tried to boost the sales by upgrading the bike from 175cc to 250cc in 1958, but this did not bring the success they had hoped for. The production of the Chimera ended in 1964 with only 119 documented 175cc bikes and another 177 Chimeras with 250cc bore. However some more bikes had obvisouly been built, but there is no documentation about it today.
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.
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 round of adding material to get the surfaces smooth to blend in with te rest of the crankcase nicely.
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.
Litte ride out with a friend. This is somehow an interesting picture as the bikes are so similar but on the other hand so different.
In front the european interpretation of an “Aermacchi” as sports bike with a light frame and without electric start. In the back the US interpretation of the bike as a two-seater vehicle with a large seat and electric starter.
I had to modify the seat pan because the gas tank that was originally on my bike had big dents that are very hard to repair. I didn’t know about the damage, because someone filled the holes and repainted it. After removing the paint this was a big surprise. I bought a replacement gas tank on ebay. It had 1972 decals, but I was sure it is not a 1972 gas tank. When it was repainted I noticed the replacement tank is about 5 centimeters longer than my original tank!
Well, the replacement tank fits, but than there is no room for the seat. I relocated the seat 5 centimeters to the back and hopefully this will solve my problem. I will have the pan cleaned and powder coated and the seat will be recovered.
I replaced the airfilter (oval type) with a new UFI part. I also replaced the faulty LUCAS flasher relay with a modern electronic flasher relay as the turnsignals did burn constantly instant of flashing.
New seals for the carb today.
Before you start:
There is no guarantee for the correctness of the information provided. That following steps describe the procedure for my 1970 GT-350. It’s a different procedure on other model years!
To my knowledge (again, without guarantee) this is valid for 1969 to 1972 Sprint 350cc street bikes and not for earlier bikes and not for the 1973-1974 electric start!
Please ailways use a few drops of oil to fit the parts together.
Here you can see how we pressed the crankpin from the flywheel and the oil dirt we found inside the crankpin after drilling out the plug. This is a typical 4-Stroke-Aermacchi problem and the reason you really should change the oil once a year or every 1000 miles. Rudolf decided the rod is used up and that I will need a new one.
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