OT IC engine- parallel twin -270 deg firing interval?

Sounds like an HD when running but smoother engine pulses and easier torque curve. No balance shaft.

The FIAT 500 vertical twin had the journals on the same axis, as it was a 4 cycle engine that produced even firing but not the greatest balance. A 2 stroke would benefit from a 180 degree crank. I dismantled a FIAT

500 engine recently and it was a 2 main bearing crank with a wacking great counterweight between the 2 big end journals. A mate joked that the counterweight provided an easy means of the mechanic gripping the crankshaft when the engine was being rebuilt. An interesting engine where the crank was cast hollow and the oil was fed in at one end.

Since you're British, I suppose you know that the first OHV British Fords, with (I think, if memory is still intact), the 105E Kent engine, 997 cc (again, IIRC) also had a hollow crank, and no counterweights?

This would have been mid-'50s, I think.

I worked on more than a few Brit bikes when I was employed in a motorcycle shop. Both pistons rise at the same time. The balance factor is the same as a single. However they are timed to fire alternately. The spark on the on the exhaust stroke does nothing. If it is old enough to have points, that setup simplifies things, as only one set is required.

Steve R.

I figured that a verticle twin would have 180 degree or a big bang- both cylinders popping off at once. So what's the crank look like? Is this firing order to make the parallel twin sound more (gasp) harley like? A balance shaft involved? BTW- this is on a triumph motorcycle "thunderbird storm" model - 1700 cc vert twin. Thanks Pat

Steve....ever do much with Royal Enfields?

Ill be working on mine this spring

Its a '61

6vt Positive Ground....I really should convert it to 12vt negative ground.

Any good *easy* ways to polish up the heads and jugs and whatnot?

It runs, but Ive never ridden it. Im sure you know the story about me owning it since 1971.....

Never have ridden it.....

Gunner

Whenever a Liberal utters the term "Common Sense approach"....grab your wallet, your ass, and your guns because the sombitch is about to do something damned nasty to all three of them.

I did Harley Davidson, Honda, Yamaha, BSA, Triumph, Norton, matchless, Greeves, and just about anything that came in. No Royal Enfields though. It was the first Harley dealer in this area, but sold the other makes, except Yamaha, as a second line. The shop was in the trade from 1913 until the late

1980s. The place was a treasure trove of old parts and manuals. I worked for the son of the founder.

Steve R.

Steve....ever do much with Royal Enfields?

Ill be working on mine this spring

Its a '61

6vt Positive Ground....I really should convert it to 12vt negative ground.

Any good *easy* ways to polish up the heads and jugs and whatnot?

It runs, but Ive never ridden it. Im sure you know the story about me owning it since 1971.....

Never have ridden it.....

Gunner

Whenever a Liberal utters the term "Common Sense approach"....grab your wallet, your ass, and your guns because the sombitch is about to do something damned nasty to all three of them.