Crankshaft

i hear lot about guys using 900 crank in 1000 motors. what i was wondering is it really gain u that much. i understand what a lighter crank does for an engine but can the 900 crank be that much lighter to even make big enough differance to make it worth while hunting down a 900 crank. stupid question but i had to ask. i figure since i got mine tore down anyway that if its worth while i might as well do it.

here's my limited impression of that combo.

this is a 1015 top end on a 73 z1 bottom end. (top end, head, cams, block, pistons)

i've gotten to ride the bike 3 times after i put this engine combo in. it has fantastic roll-on tq at highway speeds. crack the throttle and go. this is with a 33t rear sprocket and a 14t front.

the lighter crank allows for quicker throttle response. i can crack the throttle, and have the rpm's right now. all my other 1015's were a little pokey, even when tuned ok, with good weather. they had some great midrange, but they didn't rev like this one.

gotta keep in mind, i drive a high-rpm car all the time too, so i LIKE light flywheels and throttle response.

i'm looking forward to getting my carbs totally sorted. if that means keeping the 28's and living with that, good. i think that a set of 29's on this engine will be really sweet. their throttle response combined with an engine that wants to rev ought to be a great combo.

--r

Even a few grams at 11000rpm would be huge. The faster an engine will get up to speed the shorter time it takes to get peak HP. Therefore the faster the bike will accelerate. Everyone loves a rev happy bike that responds immediately to throttle input. It's possible that it is only felt in the seat of one's pants but that is your primary connection to what the bike is doing.

bike i posted in suzuki swingarm post has a 900 crank 1105 pistons ported head and 29s it revs like a pissedoff 2 stroke dirtbike,does wheelies at any speed you want flat out hauls ass!as long as you dont have a huge back tire if you run too big of a tire the 900 cranks dont have as much weight to keep them spinning when you drop the hammer!goodluck,happy wheelies:evil:

If I recall, the 900 crank was 6 pounds lighter than the 1000 crank, which is not an insignifcant amount especially at 10,500 rpm.

Post edited by: bohicabob, at: 2006/02/21 16:21

it makes more of a differance getting it to that point,once its moving the extra weight of 1000 crank is easier to keep moving.kind of a tradeoff.:whistle:

it's all a tradeoff.

wire, that motor you're talking about sounds like a total blast to ride. might have to think about something like that for next winter's project. 8^)

i had a ducati for a while, and one of the mods that everyone said good things about was to lighten the flywheel. 4 or 6 lbs, depended if you went aftermarket or just lightened the stocker. immediate throttle response on those l-twin engines, power wheelie any time you want... combine that with a set of 41mm fcr's, and you had a pretty sweet bike. too bad those mods would buy you a running kz thou...

do it, i betcha love it.

--r

solomrus:look on the suzuki swingarm kaw brake arm post ,bike look familiar?:whistle: :

yeah, i think you talked about that one a while back, didn't you? your friend over in cb that does the frames.

i do believe i have seen it at the wednesday night cruise in a couple of times.

i want that header on there!!!

--r

hes got another one in the garage,but its black im trying to talk him out of:whistle:

Ask snd u shall be told on this site. Gotta love it! i will defenitly be hunting down a 900 crank. thanks for all the info.

From a scientist point of view. that 6 lb loss equates to a loss of moment of inertia of .33 lb*ft^2. now a flywheel used to dyno 225hp snowmobile engines has a moment of inertia of 2.12 lb*ft^2. now tourque (T) is equal to Moment of inetia (I) times Angular
acceleration (A) of T=I*A. so if we treat tourque as a constant we see that if we shed a few pounds we will have more acceleration. anyone with a z1 and heavy crank wanna play on my dyno? we can see how
much this really matters.