I was looking in the Manufacturers manual for a marine Diesel twin cylinder engine recently ( It was SABB. Not SAAB, SABB. I'd never heard of it before)
Anyway, it contained this gem.
Firing Order - 1,2.
Where would we be without the manuals?
Steve
It's a perfectly valid point, though.
The order could be: 12, 12, 12, 12 IYSWIM (ie. both cylinders firing together).
Could also be 2,1 - especially important to know if it has an uneven firing cycle like my old bike did - 270 degree crank.
Out of interest, any idea why a 270 degree crank would be preferable to 180? I think I'll have a Google...
Si
Honda also uses a 360 cycle too - both pistons are in the same position, just one cycle apart.
That seems the most logical for a 2-cyl 4-stroke engine, it will probably give the smoothest gait, assuming an inline engine.
Maybe his 270 degree crank belongs to a 90deg V engine?
The idea was to make a parallel twin feel and sound like a V-twin.
There's supposedly a traction advantage for a bike, in that there's 2 power pulses close together and then a gap to allow the rear tyre to regain some grip, IYSWIM.
I think it was quite common on British bikes to have identical firing cycles on 2-cyl bikes, it gave the characteristic bike thumping sound. Maybe is was to simplify the ignition mechanism or some other reason? But it gave a lot of vibration of course.
Unlikely
especially important to know if it has an uneven
I don't think it was. Every (twin) Brit bike I had anything to do with had one up one down.
Steve
Are you sure about that? - it was the Japs who did the 180 degree firing cycle - old Brit. bikes were famous for firing both pistons at the same time.
I'll give you that, I tangled myself up there :-))
Steve
The one's I'm thinking of are, yes. It was used a lot in the Honda 2 cyl. cars and vans from the 70's and 80's.
Dunno, I've not seen a strange angled crank, but certainly they exist.
That is there to stop you firing it up in reverse.... ;-)
Smooth power delivery but a horrible thing to balance. Suzuki tend to have them 180 degrees out - easy to balance but lumpy power delivery from idle. I've ridden both and prefer the Suzuki - much more smooth at speed.
My father's Triumphs, (Bonneville and Speed Twin) fired alternatly but the pistons rose and fell together.
I've only ever ridden a CB400N twin, and I honestly couldn't remember what layout that was. It was a rough old thing anyway.
The one's I have in mind are indeed used in cars, they were fitted in the old N and Z model Hondas of the 70's, both as 360cc air cooled and a
600cc liquid cooled versions. It was also used in the Acty vans too. They were quite smooth, and only used a single carb, so balancing wasn't a problem. Not bad performance either, the Acty vans could top 80mph.MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.