Stroke it.. .. .. 750cc's is just 11.1 mm away! haha!

FinalImpact

FinalImpact

2 Da Street, Knobs R Gone
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If you stroke the Crank 11.1 mm (0.437") the 600cc jumps to 750cc's. So now we can all have a big debate over buying another bike! :eek: Anyway, I was just curious how much additional stroke was needed to "obtain" 750...

Of course you need custom pistons made so they don't smack the cylinder head, that R6 header with the lager ID pipe becomes very useful, you need fuel management and bigger injectors/throttle bodies, some head porting and the air box mod now becomes meaningful. blah blah blah - list goes on...

Bene:
As the bore to stroke ratio nears square - the torque output goes up!

Stock:
Bore 65.5 mm, stroke 44.5 mm (2.58 × 1.75 in) X4 = 600cc

Stroked to 750:
Bore 65.5 mm, stroke 55.5 mm (2.58 × 2.187 in) X4 = 750cc

I'm guessing the crankcase has room to allow for such things with a little massaging if someone wanted to to such things...

/the end
 
A couple things to consider.

I'm no mechanical engineer (I did stay at a Holiday Inn express last night!), but if you stroke your engine without changing the engine head, your compression ratio will go up.

As I understand it, compression ratio is just the volume of the combustion chamber at bottom dead center divided by the volume at TDC.

Torque increases because you increase the length of the con rod, which increases the lever arm used for force application from the combustion event, and hence increases torque by definition. This is the equivalent of using a cheater bar on a stubborn bolt.

I have noticed that a lot of engines with longer strokes tend to have lower max RPMs. I'm not sure why; Maybe it's because it just takes longer for a long con rod to complete it's path of revolution. Maybe it's because the longer rods can't take as much stress before snapping.

Having said that, if anyone strokes an FZ6, that would be really cool. I would have to demand pics. :D

edit: Smiley failure!
 
CrazyBiker said:
You forgot the FZ8. It is a nice bike with the right suspension...
Click to expand...

I like the theory of the FZ8 - until I sit on one. The seat is wide, flat, hard and high, making it feel even higher than the FZ6 - Styling wise - it looks good, and you're right - the suspension is mucchhhh better than ours.
 
Water Bear said:
A couple things to consider.

I'm no mechanical engineer (I did stay at a Holiday Inn express last night!), but if you stroke your engine without changing the engine head, your compression ratio will go up.

As I understand it, compression ratio is just the volume of the combustion chamber at bottom dead center divided by the volume at TDC.

Torque increases because you increase the length of the con rod, which increases the lever arm used for force application from the combustion event, and hence increases torque by definition. This is the equivalent of using a cheater bar on a stubborn bolt.

I have noticed that a lot of engines with longer strokes tend to have lower max RPMs. I'm not sure why; Maybe it's because it just takes longer for a long con rod to complete it's path of revolution. Maybe it's because the longer rods can't take as much stress before snapping.

Having said that, if anyone strokes an FZ6, that would be really cool. I would have to demand pics. :D

edit: Smiley failure!
Click to expand...

True, adding stroke will change the C/R, but it MUST HAVE a custom piston so the Piston Doesn't rise above the deck smack the head! With the NEW Piston, volume can be altered to raise or lower compression. And yes, as the stroke increases, so does the piston velocity which usually lowers an engines RPM to keep it healthy.


Here is some htm code I wrote a long time ago to calculate compression ratio. If you wish to tinker, save that text file REMOVING THE .TXT extension leaving it as "CompRatio2.htm" click on this, it should open in your browser and allow you to do some playing.
Screen shot is all just a WAG for gasket, valve relief, skirt clearance, ring land height, gasket volume, all the critical data needed to accurately determine C/R blah blah blah.....
SEE ATTACHED Text File Below screen shot.

48564d1370969724-stroke-750ccs-just-11-1-mm-away-haha-600cc-compressioratiocalculation-jpg
 
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Anything is doable.


Remember the sign at the garage in Mad Max? "Speed is a question of money, how fast do you want to go?"


Here's a few suppliers who can make what you want:

1) Pistons: JE Pistons Manufactures Quality Forged Pistons for the Domestic Automotive, Sport Compact, Powersports and Racing Markets

2) Rods: Powersports

3) Cranks:

APE Race Cranks...
High Performance Products/ Falicon 727.797.2468

While you're in there may as well add a cam: Web Cam Inc. - Performance and Racing Camshafts
 
Don't forget, larger combustion=more heat.

I think better material for the con rods would be needed, due to the whole inertia thing.

I do love the idea of sleepers.
 
FinalImpact said:
True, adding stroke will change the C/R, but it MUST HAVE a custom piston so the Piston Doesn't rise above the deck smack the head! With the NEW Piston, volume can be altered to raise or lower compression. And yes, as the stroke increases, so does the piston velocity which usually lowers an engines RPM to keep it healthy. /attachment.php?attachmentid=48564&stc=1&d=1370969724[/IMG]
Click to expand...

I could talk about this stuff all day. I'm in the large class of people who find engines interesting, but have no practical knowledge in dealing with them.

Cool beans!

Edit: Oh, something else I recall reading from Kevin Cameron in a Cycle World issue: Speaking of cranks, if you knife edge the cranks (to reduce drag while they turn through the oil), you reduce the reciprocating mass of the crank. Sounds like a good idea, but the extra weight of a crank serves as a kind of flywheel -- more rotational inertia means the crank accelerates more slowly.

In other words, I've read that super light cranks can cause the engines to go rev-happy.
 
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Water Bear said:
I could talk about this stuff all day. I'm in the large class of people who find engines interesting, but have no practical knowledge in dealing with them.

Cool beans!

Edit: Oh, something else I recall reading from Kevin Cameron in a Cycle World issue: Speaking of cranks, if you knife edge the cranks (to reduce drag while they turn through the oil), you reduce the reciprocating mass of the crank. Sounds like a good idea, but the extra weight of a crank serves as a kind of flywheel -- more rotational inertia means the crank accelerates more slowly.

In other words, I've read that super light cranks can cause the engines to go rev-happy.
Click to expand...

Remember; those balance counter weights are there to offset the combined weight of the pistons, wristpins, and rods. You can't just knife them AND maintain balance of the reciprocating parts. Mallory is a heavy metal used to add back mass to make these efforts possible. The other option of course is to lighten the pistons/rods but that comes at a cost too.
 
Water Bear said:
I have noticed that a lot of engines with longer strokes tend to have lower max RPMs. I'm not sure why; Maybe it's because it just takes longer for a long con rod to complete it's path of revolution. Maybe it's because the longer rods can't take as much stress before snapping.
Click to expand...

The longer the stroke, the faster the linear piston speed (piston-to-cylinder wall speed) at a given RPM. The greater the piston's velocity, the more force it exerts on the rods, cap bolts, bearings, cranks... when it switches directions at the top & bottom.

As for stroking it (get your mind out of the gutter!) I'm pretty sure it's been brought up here before. My theory is that Yamaha probably didn't leave much (any) spare room in there. It's an R6 engine, not something from the 80s, a lot of clearances have already been minimized to increase efficiency, reduce weight, and make a more compact engine. 5.5mm doesn't sound like much, but it can be when you're trying to leave room all around a crank that can spin 12k RPMs. You could gain a little without increasing the actual throw radius by offset grinding the rod journals, but then you need longer rods and/or an even shorter piston skirt. And you need either a taller deck height (notgonnahappen) or an even shorter pin-to-crown on the pistons, on top of the already reduced volume to keep the CR in check.
 
Re: Bore & Stroke.. .. .. to--> 750cc's

FWIW:
If you keep the B/S ratio the same (BORE & STROKE, not BS), it comes out like this.

Stock:
B: 65.53mm, S: 44.45mm, B/S R: 1.474:1 @ 599.6cc

750 cc w/same B/S ratio:
B: 70.73mm, S: 47.87mm, B/S R: 1.477:1 @ 752.7cc

Change:
Bore: +5.20 mm, Stroke: +3.42 mm

Basically a new everything (Block Sleeved, Crank weld & ground, Rods & Pistons! Plus the head won't flow enough air so the net gain is zero! :rolleyes:
Why?: I was curious about the overall block dimensions from 600 to 750 cc's. Not that keeping the B/S ratio the same is advisable.
/thread Blah
 
FinalImpact said:
True, adding stroke will change the C/R, but it MUST HAVE a custom piston so the Piston Doesn't rise above the deck smack the head! With the NEW Piston, volume can be altered to raise or lower compression. And yes, as the stroke increases, so does the piston velocity which usually lowers an engines RPM to keep it healthy.


Here is some htm code I wrote a long time ago to calculate compression ratio. If you wish to tinker, save that text file REMOVING THE .TXT extension leaving it as "CompRatio2.htm" click on this, it should open in your browser and allow you to do some playing.
Screen shot is all just a WAG for gasket, valve relief, skirt clearance, ring land height, gasket volume, all the critical data needed to accurately determine C/R blah blah blah.....
SEE ATTACHED Text File Below screen shot.

48564d1370969724-stroke-750ccs-just-11-1-mm-away-haha-600cc-compressioratiocalculation-jpg
Click to expand...
Randy, I used to think you had to much time on your hands, now I'm convinced that you do lol.

Nelly
 
Nelly said:
Randy, I used to think you had to much time on your hands, now I'm convinced that you do lol.

Nelly
Click to expand...


Had to find my own chart to do some calculations for a friend. Then I got side tracked! lol Come Jan its new job time! ;x
 
Call me a cynic, but you put a whole lot of effort into maybe keeping up with an R6. Seems like alot of work for little gain.

Could you not overbore a few .000 and get a better result without turning all stroker?


Screw it, R1 engine with an r6 crank de-stroker :D :D
 
Last edited:
FZ09Bandit said:
Call me a cynic, but you put a whole lot of effort into maybe keeping up with an R6. Seems like alot of work for little gain.

Could you not overbore a few .000 and get a better result without turning all stroker?


Screw it, R1 engine with an r6 crank de-stroker :D :D
Click to expand...

I believe the cylinder is PLATED(a coating).

To increase the bore would require a complete engine break down(as the cylinder is part of the upper block), punching it out and going "old school" with cast iron cylinders pressed back into the block..

There were some comapanies MANY years ago that would re-plate a cylinder(late 70's, had it done on a YZ250). The plating is much more efficient in the cooling department too..

Checking the parts web site, Yamaha doesn't sell over sized pistons so custom pistons /rings, would be necessary as well.

That's if there's enough room between cylinders (probably NOT likely)..
 
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