Moto Guzzi Airone

Charming as the 254 was it wasn't for me. I saw myself reflected in a shop window sitting on it and it looked like Lurch astride My Little Pony! It's tiny! Also I'm more into thumpers than whiners. And a whiner it definitely was! Interesting little project but when finished I had to make room for something else. So when I got the chance for a part exchange with a little Guzzi thumper it was a choice easily made. Enter the Airone.

So another 250? Yes but apart from the name on the tank and the small size they could not have been more different. Small again unfortunately but not as small as the 254. Although having only 12 hp (well according to the specs and it’s a Sport, so 2,5 hp up from the normal one!) this is actually great fun to ride! It handles surprisingly well for a bike designed in the 1930’s. Although mine’s from 1950. It puts a smile on my face every time I take it out. Top’s about 90 kph, or so my mate, riding behind me, told me. Because a speedo was optional and something the first owner never bothered with. So what’s to tell? It came from Italy obviously, one of the previous owners contacted Guzzi and was sent the details of year and date of delivery and the name of the first proud owner in Italy. Then it somehow ended up in Belgium where it was last registered before I got a Dutch registration. Oddly enough the Belgian papers show the year of manufacture to be 1948, which is unlikely because in that year they came with hydraulic rear shocks. They were apparently not up to the job and by 1950 Guzzi reverted to the old friction shocks, as mine has. Because the current registration had to be based on the last known one, the Belgian, the year of build states 1948. Incorrectly in my opinion, but who cares.

Optical she came to me pretty much as on the photo above. I’m not sure if the paint’s original or if it’s an old restoration. But I liked the patina so she’s going to keep showing her age. It’s a bit scratchy here and there and the chrome a bit flaky and rusty but that’s OK.

The person I got her of is a farmer with quite a collection of oldies near Alkmaar. His shed was filled with bikes of diverse plumage and even a Guzzi Hercule! He had many projects going and not enough time for the Airone. Which had been standing in the corner for years. He actually got it running a bit but she was a heavy smoker! Also the petrol was leaking out at an alarming rate so I asked him to give up his resuscitation attempts because I wasn’t going to ride her home anyway. The block was loose, no play on the flywheel I could feel and a bit of compression. How much should it have? Not very much was my guess. It seemed complete. The tank is not original, it is (I stand to be corrected) known as a MiTa tank. This was an aftermarket tank named after the Milan – Taranto rally. This was run back in the days and required a larger tank capacity than standard. The rally is organised again nowadays I think for classic vehicles. The tank was lying loose at the rear where bolts were cut off and a bracket seemed to be missing. The cables were bodged but the electrics seemed OK and the magneto was supposedly overhauled by the Belgians. The spark was good anyway.

Over the winter 22-23 I had time to look things over and get her running if possible. The engine innards gave the impression they may have been OK so I thought I could get away with leaving that as it is for the time being. The heavy smoking possibly due to wet sumping after standing idle for many years. Started off with installing a homemade muffler in the completely open fishtail as it made a right racket when the farmer had it running. And I really dislike noisy motorbikes. Then made up some new control cables and tidied them up. Ordered new petrol taps and restored the mounting bolts a the rear of the tank. The holes in the front flanges of the tank were worn wide because the crossbolt was loose and the whole tank could move to and fro. So soldered two washers onto the flanges. Then made up a new support bracket to mount the rear. Found a photo of a tank with the original bracket on Ebay for an example. That was a stroke of luck! Also fitted an oil tank tap to prevent future wet sumping. Made a switch on the tap which sort circuits the ignition so I cant’t forget to open it. Turns out it’s also very handy for switching the engine off! Cause there is no kill switch and it doesn’t react to the key of course. Adjusted the spokes of the rear wheel which had quite a wobble. The rear wheel was loose in the forks and had the wrong nuts fitted which had knackered the threads on the axle. New nuts and welding up and machining off the axle and cutting new threads solved that. Same for the rear fork axle. Installed a bronze bushing in the brake paddle hinge and a new steel one it pivots on.

 

New mounting points soldered on the tank

Aluminium casing welded above and right the gearcam that was "out".

Then last spring came the big moment, does it run? Well it did….. But still chain smoking and leaking. Also found out its was impossible to engage fourth gear. So nothing else for it, the engine had to come out and taken apart. To take the engine from the frame, according the manual, cilinder and head need to be removed first. The headbolts turned out to be just losely fitted and a cooling fin of the cilinder broken off. But on the upside the piston cilinder lining and valves were like new. I also had to get used to the whole setup of the little engine, not having worked on bikes this old. The clutch setup with a central spring on the left, outside of the front sprocket, the clutch itself on the righthand side, with a "pulling" rod through the driveshaft and a set of brass plates against  a set of steel ones, lubricated by the oil mist from the engine casings breather. This oil collects in the clutchhousing and will cause the clutch to start slipping eventually, when not drained regularly.The oilseals were all made of felt with a screwback section on only the driveshaft. All oldschool engineering now I suppose but new to me.

The insides looked pretty good apart from a crack in the lefthand half of the casing that covered just about the whole circumference of the bearing housing of the bearing behind the clutch. This was a bit of a setback but I managed to weld it back together again eventually. The gearcam on the gearchanging shaft that connects to the gearchange control drum turned out to be one tooth out, which caused the 4th gear problem. So after fitting new gearbox bearings and felt seals the whole shebang could be put together  again. On the gear of the magneto drive is a fairly large felt seal that turns along with the gear and presses against the aluminium casing behind said gear. Over the years this has produced considerable wear on the casing. So to stop this wearing further I machined an aluminium plate with a modern seal which is sandwiched between the magneto and the casing.

After all that, halfway 2022, the engine was back in the frame and was finally ready for the next starting attempt. This was partially successful, as in that it started but stalled when the throttle was opened. To get this right it took a lot of fiddling with the carb, which happens to be the much sought after (or so I'm told) Dell'Orto SSF. Because this if of course an Airone Sport(!) with an impressive 11 hp as opposed to the measly 8.5 of the ordinairy "Touring" :) Anyway after much kicking and a smattering of swearing she finally ran reasonably. Carb needs a lot of priming and she won't pick up before having properly warmed up. The exhaust note turned out very civilised with the homemade muffler and I think she runs quite well with it, despite the rumors on the web that they need to be "free breathing" as to not diminish the already scant powersupply. The other problem was that the scavenge oilpump did not seem to pump the engine oil back to the tank. Resulting in a full sump and matching smoke curtain. This is a vane type pump, one side of the vanes run against the pumphousing and on the other side they run against the backside of the big plug that you can see on the outside of the pump. The pump was rotating ok but not pumping. Under the edge of the plug there was a fiber washer that served as a gasket I presumed. It was quite thick so I put in a thinner one which reduced the space between vanes and backside of the plug to 0,3mm. Figuring the pumpaction would improve due to less loss past the vanes. Turned out that 0,3 was still too much. I experimented with layers of paper washers untill there were actually none left but the pump worked and didn't seize!

 

Oilpump with the brass plug.

So after sorting out the registration, I could take her for the first ride. And I must say that, despite the fact I'm also way to big for this 250, it put a big smile on my face. Despite the humble specs it actually does want to roar. It gladly thumps around at 40 kph but drop to third and open up the throttle and away she goes. Okay not mindblowing of course but you can definitely detect the Guzzi racing heritage of the period in there. Or is my imagination running away with me? Anyway I enjoy the little rides through our neighbourhood.

Still a few things that need sorting. I've put on a new front tyre and sorted the front brake out, it actually slows you down now! And the forks need to come apart somtimes but there's no rush.