Triumphrat

ravencall

Returning to motorcycling after 20 years, last bike 1962 BMW R60, old iron bike, no plastic, with Earls Fork, opposed twin- 180 crank, real, real smooth, practically vibration free. Question about Ameica (?), with the 180 crank the firing should sound like a 1940's John Deere Tractor, #1 fires then 180 degrees later #2 fires then 540 degrees later #1 refires, although the firing cycle sounds strange, the pistons traveling in opposite directions, #1 going down while #2 is coming up, the forces should balance themselves for a pretty vibration free machine. AM I RIGHT ????? :???: :???:

EnglishWombat

NO!

You are completely wrong! The America fires at 270 degrees, and somehow still doesn't shake it's self to pieces. (However that could be due to the massive weights on the balence shafts in the engine).

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Gina

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ravencall

Gina,

I'm an engineer and auto mechanic from way back, A 4 cycle engine fires once each second revolution - down on power, up on exhaust(thats one rev) then down on intake and upon compression(thats the second rev) or one power stroke each 720 degrees, how do youexplain a 270 degree firing cycle? :???:

ravencall

Gina,
Following up on the previous response, I called the Triumph dealer in Wenatchee Washington and asked him about the crank on the Triumph America. He confirmed with his shop manager that the America crank has connecting rod journals, commonly called crankpins, separated by 180 egrees, when #1 is on top dead center, #2 is on bottom dead center. The advertising guys may call it 270 degree firing cycle but thats only because it is a symplistic way of say the longest interval divided by 2 ( 540 degrees/2=270degrees). In a "normal" 4 cycle, 2 cylinder vertical twin, both pistons are on top dead center at the same time, one completing compression and firing, the other completing exhaust and starting intake. One ful rev later the second one fires - 360 degree firing cycle. I have yet to test ride a Triumph but look forward to it and the dealer has both Americas (270 firing cycle?) and Bonnevilles (360 firing cycle) in stock. It's been many years since I sat astride a "Limey Machine" (no offense) but they were the best there was in the 60's and I'm in hopes the new Triumphs are even better.
Dave

TOMKRILL

I always looked at it like two engines with a common crankshaft.

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zmilin

isnt the bottom line that it really doesnt vibrate! I have two 07 Americas...they barely vibrate and they run quiet.

If you want to do some test riding Cycle Barn will have the Triumph truck at Lynwood CB on Fri and Sat.

ravencall

Thanks zmilin, that's what I wanted to hear, the vibration is minimum if at all. And technically speaking that should be so at practically all revolutions as the pistons traveling in opposite directions balance each other.

Thanks for the feedback

Dave

tba-golfer

raven-

You had my head in a twirl with your engine expertise.
Just ride then buy the America.

You'll love it.

:wink:

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ravencall

Thanks TBA-Golfer

I've been looking at all the Japanese stuff nearby but somehow my heart goes back to my youth. I know I don't want a Harley, just see too many used ones for sale. And again Technically there is no way to truly balance an engine that has all the reciprocating mass near the same point on the circle, be it the same point as in the Bonne or in one or two crankpins like the V twins. The idea of listening to an America at idle is intriguing and I remember the reputation the 250 Honda Hawk Scrambler had in the early sixties - one tough, stay together bike, race after race. I was so intrigued that in 1967 I bought a beat up Norton Commando for the specific purpose or rebuilding it with a 180 crank. In `68 I went back to college in engineeringand that project went unfunded. Well time goes by and we get older

Dave

bugger1

yes I agree with you ravencall, the pistons on my Norton commando do came up at the same time, these new triumphs have a counter weight cranks thats why there so smooth and don't vibrate,you really should do yourself a favour and take one for a test ride you will be amazed. they have changed alot from the sixty's, no bad wiring problem. there short stroke motors, they don't blow up as easy and very reliable,
I still love my old girl Norton though, there 2 very different rides.

cheers

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Love to ride with friends on a sunny day with the sound of Triumph & Nortons