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On a twin if the pistons go up and down the same time is that a 180 or 360 engine?

Champ
 

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i thought it was a 360 like 95% of the time, only unless its a twingle.

jc
 

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It's almost always a 360.
But yeah...like both of them dudes say....almost.

360 means that each cylinder fires 360 degrees of rotation from the previous cylinder. Technically all you'd have to do to make them both fire at the same time would be to re-grind the camshaft. Assuming it was a four stroke.
JohnnyB
 

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if they both go up and down at the same time, its a 360. (triumphs and early type1 only honda twins i think right?) I could have that all backwards though. at least i was told that the type1 hondas were 360 cranks. i have yet to actually look to see on the 2 i have still together.

if one goes, then the other, its a 180. so each cyl would fire at 180°. if they both go up and down, they still fire at 180° right?? or youd have like a kawa/duc big bang motor. so does it relate to cam timing, or crank config? i always thought crank figuration. since you can vary cam timing and valve overlap.

you could also just wire the ig to fire both sides, but youd have the cam timing all out of whack. itd be interesting to hear a twin with the correct timing on one cyl, then the 180° out on the other. triples is where it gets real weird. and v-twins. im sure the v5's of gp have some really weird crank configurations if you looked at it from a classic point of view.

j
 

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I concur, re: Triumph twins. Anyway, that's how it was explained to me by engineer/mechanic pal-o-mine, years ago rebuilding top end on my Bonneville.

Didn't know any Honda twins were 360, tho. I've got several 350 motors & watching the pistons, I always figured 180, which I assumed would run a bit smoother than the Triumph. However, I just picked up a '68/69 type-1 motor, which I've heard has a slightly hotter cam (is this true?). It has "Type-1" stamped into the points cover. If it's a 360 degree crank, does that mean it's going to sound more Triumph-y? That would be sweet.
 

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I think the only Honda bigger twins that were 360 crank are the 305's designated as "CP". These were the police specials. Joe, I think you have one. But I think all of the 350's were 180 cranks (I could be wrong but I wouldn't bet on it).

BTW I rode the Triumph to work today. Its going to get up to 75 by mid day. It hasn't rained in 50 some odd days. I don't even really have any rain gear out here.

Mike O.
 

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All Honda 160's, 175's, and CB200 are 360 degree engines. Both pistons go up and down at the same time. However they alternate firing. Left side goes to TDC (compression)..fires....crank rotates one time...right side is at TDC (compression)...fires....crank rotates one time...left side is at TDC (compression).. fires.....etc.

Don't confuse "firing" with ignition....these bikes can use a one dual outlet coil because you can send spark to both cylinders at the same time...only one is at TDC on the compression stroke...so only one fires. A 360 degree twin has combustion every rotation of the crank...that's why they sound like two strokes at 12,000 rpm.

I call these engines "360 Engines" instead of 360 degree cranks...because...with the SAME crank and a different cam you could combust both cylinders at the same time if you wanted....which would be either a 0 degree engine or a 720 degree engine.

Probably the safest way to discuss it is to talk about crankshaft offset....how many degrees one crank journal is offset from the other....if they are on opposite sides of the crank....a 180 degree. If they are on the same side....0 degree or 360 degree....depending on the camshaft.

Can get real complex with more than two cylinders.

JohnnyB
 

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the honda dream 305 is a 360 degree motor. The superhawk and 305 scrambler are 180 degree engines. I always thought that was really funny because externally the engines look the same.
 

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That is kind of curious, wonder why they did it. I've talked to people who have pressed apart 175 cranks and put them back together as a 180 and then had a new cam ground up. They could never find a definative answer on the dyno as to what made more power. Seemingly not enough difference to matter. I prefer the 360 degree on a small bike because it make the ignition system much simplier and lighter.
JohnnyB
 

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I thought someone told me once that because of the mild cam in the type 2(Dream) motor it made it easier to start due to the extra crank momentum
 

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quote:
That is kind of curious, wonder why they did it. I've talked to people who have pressed apart 175 cranks and put them back together as a 180 and then had a new cam ground up. They could never find a definative answer on the dyno as to what made more power. Seemingly not enough difference to matter. I prefer the 360 degree on a small bike because it make the ignition system much simplier and lighter.
JohnnyB
From the people I have talked to (old crusty honda techs who worked on these bikes back in the day) it was to give the bike a more british "feel". Honda saw the dream as the touring/commuter bike of the line and wanted the bike to have the same appeal as a triumph or bsa.
 

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Hey...what is an old Yam XS650? They are 360's right?
That was my first brandy new bike...a 77 XS650...loved the way that front wheel moved an inch back and forth at idle.

Bill,
That makes sense....engine could rotate a full turn or so to build up momentum before a compression stroke.

Did the Brits do a "twingle" 360 degree twin at some point? Both pistons up and down at the same time and firing at the same time?
JohnnyB
 

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quote:
Hey...what is an old Yam XS650? They are 360's right?
That was my first brandy new bike...a 77 XS650...loved the way that front wheel moved an inch back and forth at idle.

Bill,
That makes sense....engine could rotate a full turn or so to build up momentum before a compression stroke.

Did the Brits do a "twingle" 360 degree twin at some point? Both pistons up and down at the same time and firing at the same time?
JohnnyB
I know Puch did with their 250s and 350s. Even had a shared combustion chamber. There are some small italian bikes like that too. Not sure of the brits as a factory bike but here is a triumph 750cc twingle flat tracker:

http://www.team3dracing.com/wfo_view.php?id=29&offset=0&listoffset=0
 

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bfd-- how ya doin? Didja winterize the duc? i took mine out last weekend, still need to tend to it . . . .
 

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stan lippert told me the type one motors all had different cranks. i thought the type1 designation was a first model year thing but he corrected me and said that the type 1 motors were not all first model year bikes but ones that had the 180(ooops sorry, 360°) crank. at least thats what i though he was saying. the cp77 305 that mikes talking about is a type1. and of course they made type1 cb350's. i thought a type 1 was automatically a fat cam model, so when i sent stan 2 heads from type 1 motors, he said only 1 was a 68 head even though the other was still a type1. (all 68 cb350 motors had 6mm exhaust studs, thats how you can tell) ill check the other type1/68 cb350 motor i have tomorrow and see what it does, if anyones interested.

jc



Edited by - joe c on Dec 10 2006 12:12:55 AM
 

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I don't know why Honda made 360 deg off set cranks on some models and not others but one difference is that a 360 deg crank engine lends itself to tuned merged exhaust pipes. According to Todd you can't really get any advantage with a 180 deg crank engine by merging (2 into 1) the exhaust pipes but you can with a 360 deg engine. I'm not an expert but it does seem to me that making use of the exhaust pulses from one cyl to favorably influence the other cyl would almost demand that they be on the same timing between the pulses. If that makes any sense to anyone please let me know. I'm wondering if I have any idea of what's being talked about or whether the Pacifica Clara I'm drinking right now is working.

Mike O
 

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Mikey,
From all I know you are right on the money. That's why I only do 2-1 exhausts for 360 degree 175 twins.

JohnnyB
 
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