how to raise max RPM's

hardr0ck68 wrote: "In his post he stated a "safe" piston speed of 4500fps..."

OK, it’s back to arithmetic class for you guys.

Let’s multiply 2.13 INCHES times 11,000 Revolutions per MINUTE:

I get 23,430 INCHES per MINUTE.

Let’s divide 23,430 INCHES per MINUTE by 12 to get FEET per MINUTE:

I get 1,952.5 FEET per MINUTE.

Let’s divide 1,952.5 FEET per MINUTE by 60 to get FEET per SECOND:

I get 32.5 FEET per SECOND (fps).

However, remember in one revolution the piston makes a trip up and down the cylinder, so we need to multiply 32.5 times 2 to account for the round trip per revolution. I then get:

65 fps.

I won’t show the math, but 65 fps = 44.3 mph

4500 fps = a whopping 3068 mph; literally “faster than a speeding bullet”

will61310 wrote:

are you telling me all the stroker 'busa shift at 8,500?


Now you're just being stupid, comparing a kz650 to a busa??:dry:

just in that i would imagine a stroked modern liter bike would very close to the same stroke as the 650. So unless physics has changed in the last 30 years or busa's use parts from metal that cannot be found from wiseco or atp then I don't see why the two cannot run similar piston speeds.


I just checked, a busa runs a stroke of 63mm and falicon offers an 11mm stroker crank for a total stroke of 74mm. Man they must have to shift at 5g to keep that thing from coming apart :blink: :laugh:


So how is it a busa can run higher piston speeds? depleted uranium con rod bolts? Ti pistons?

650ed wrote:

hardr0ck68 wrote: "In his post he stated a "safe" piston speed of 4500fps..."

OK, it’s back to arithmetic class for you guys.

Let’s multiply 2.13 INCHES times 11,000 Revolutions per MINUTE:

I get 23,430 INCHES per MINUTE.

Let’s divide 23,430 INCHES per MINUTE by 12 to get FEET per MINUTE:

I get 1,952.5 FEET per MINUTE.

Let’s divide 1,952.5 FEET per MINUTE by 60 to get FEET per SECOND:

I get 32.5 FEET per SECOND (fps).

However, remember in one revolution the piston makes a trip up and down the cylinder, so we need to multiply 32.5 times 2 to account for the round trip per revolution. I then get:

65 fps.

I won’t show the math, but 65 fps = 44.3 mph

4500 fps = a whopping 3068 mph; literally “faster than a speeding bullet”

my bad, leave it to me to screw up a plug and play formula... however i used the formula beatpoet gave correctly i believe just used fps not fpm as he had listed. Again his post claims a "safe" limit of 4,500 fpM

Timbomb already showed you an example that came apart at less piston speed than that....

paper mache pistons are able to spin faster...also.....using wd-40 instead of that heavy old engine oil...plus never forget ...wheight equals power loss.....train a monkey to pull the trigger

This guy is like a little kid...You know,when you tell them NO, but they keep asking and asking and asking,trying to get you to say yes. I consider Larry C. to be somewhat of an EXPERT on these engines,and if HE doesnt think it possible, then apparently it cant be done.. Anybody know what rpm's Lorcan is shifting at? Im quite sure he has done Vast research,and spent more time and money than this guy is ever gonna put into his...

(youtube)


this surfer knows about rpm's

hardr0ck68 wrote:

will61310 wrote:

The most knowledgeable people on this site tell you what to do in order to make power with a 650 many different ways,yet even though they tell you the rpm limits, you seem like you will argue your point till you get the answer you WANT to hear..Wow, i cant believe this is still going on...

No, I will keep asking questions and getting information until i think I know the limits and how to push them....

Exactly what is it you want out of the engine? At first the thread appeared to be about you wanting to spin it at high RPM.

It's getting into a "practical vs possible" debate without any clear objective to be achieved.

Outside of people saying forget it, you've stood solid with determination of achieving something....I don't think anyone knows what that is though.

If you laid out some specific, clearly defined objective, then people could & would [I think] help you.

As it is, you're just aimlessly pissing in the wind....

You have to generate enthusiasm about a project if you intend to receive help. Then when it's offered to you it's rather customary to show a little gratitude now and then. I don't see a single "thanks guys" anywhere....

People's time and experience may be given freely but there are limits to how much anyone will help if they get frustrated form lack of direction and/or appreciation.

JMO...but I do believe it's time to step up to the plate and swing the bat at the ball rather than sitting on the bench telling everyone that hitting a home run with a baseball bat and a football is possible.....especially when they've been playing with a hardball for a long time...

So there it is kid....it's your play

After all is said and done - he's building a 750..

I am sorry if it seems I am ungrateful.

I am honestly thankful for all the good information given in this thread. It just seemed to me that raising the rev limits is a way of increasing power that is little thought about.

I was just looking to pick more knowledgeable peoples brains.

I am not really appreciative of people saying don't do it, or buy a new bike, because those posts are non-productive.

The thread was started so I could learn what are the reasons the rev limit is 9,000 and what limited it to that level.
Valve float was not mentioned and I was surprised but piston speed and rod stretch were.

Then I was informed that these motors could not make power there, for design reasons however I still don't understand that so well. I believe someone mentioned that the 2 valve head cannot flow enough, and when made to it becomes a very peaky/ hard to ride engine.



My personal goal, which is different from the discussion in the thread (because I am trying to look at many different power adders) is to build is a streetable (and still easy/fun to ride) 100hp kz650. It will not be 650cc's by the time its done, and it may or may not go turbo. I have no problem taking years to collect the parts and put it together right. Also if it red-lines at 9g I am alright with that. I am just asking questions to learn how to make the power, and why rpm's are not a commonly talked about part of the equation.

I will not be satisfied with simply going to 810 and excepting that as the final end all for a kz650 based engine.

I have always been a bit of a hard head, but please understand I am only saying the things I say because I do not fully understand the reasons involved. I do not mean to offend anyone; and I am not taking offense to your pokes at me... I come to this forum to learn about this bike and it's powerplant... not to piss folks off.

:laugh:

Well said :silly: