how to raise max RPM's

hardr0ck68 wrote:

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.

You don't offend me. I rather admire people who will stick to a dream and see it through to completion.

Hopefully you can complete yours. It's going to be expensive. But then again...what isn't these days

lol, you guys don't honestly think that that Gixxer spit a piston and rod out the top of the engine do you?

something came out of the top of that engine and raised the gas tank as it went by,looks like a piston/rod bouncing across track to me.

Says on utube that is is a plastic air induction piece. Sure looks like a piston to me.

Here is his web site. Check out the video on his first time out run. Roy


www.brocksperformance.com/media/gadson_crash05.wmv

roy-b-boy-b wrote:

Says on utube that is is a plastic air induction piece. Sure looks like a piston to me.

Here is his web site. Check out the video on his first time out run. Roy


www.brocksperformance.com/media/gadson_crash05.wmv

that poor bastard just can't catch a break.

not to get yelled at again, but to plumen I was under the impression (and this very well might be wrong and if so please gently let me know...my asbestos boxers are hot enough already) that the z1 style motors had an rpm limit based more upon the roller bearing cranks than anything.

So yeah there are no con-rod bolts to stretch, but at some rpm those roller bearings would stop rolling as meant and spin out.

Now this is something I heard from a very well informed man, who has owned more than one z1, with a dra racing background, and currently owns a turbo z. I won't use names because if it is deemed wrong I do not want to be the one to mis-quote or spread information taken out of context. SO again if I am wrong then please don't set my balls on fire for it!

I might be misinformed, but am thinking valve float is the primary risk when exceeding normal redline, and that stronger valve springs allow a safer rpm increase beyond normal redline with the stock springs.

The idea being to avoid having the valves collide during hign rpm because they aren't closing fast enough.

Have not considered the needle bearing crank as a particularly limiting factor with regard to spinning in excess of normal rpm redline. Or the plain bearing crank either for that matter.

Am recalling most dyno charts show maximum horsepower dropping off shortly before reaching redline. Interpreting to mean that higher rpm alone does not assure an increase in horsepower.

Good Luck!

hardr0ck68 wrote:

not to get yelled at again, but to plumen I was under the impression (and this very well might be wrong and if so please gently let me know...my asbestos boxers are hot enough already) that the z1 style motors had an rpm limit based more upon the roller bearing cranks than anything.

So yeah there are no con-rod bolts to stretch, but at some rpm those roller bearings would stop rolling as meant and spin out.

Now this is something I heard from a very well informed man, who has owned more than one z1, with a dra racing background, and currently owns a turbo z. I won't use names because if it is deemed wrong I do not want to be the one to mis-quote or spread information taken out of context. SO again if I am wrong then please don't set my balls on fire for it!

yep,youre absolutely correct about the roller bearings becoming sliders.of course the way i build em the rev limiter on my pacemaker kicks in long before 10,000,ill build you a large x huge kz motor that will have you seeking therapy by 8500-9000 rpms! :woohoo: have you ever tried holding down a 1327 motor in a stock wheelbase chassis at 8000 on the street? :laugh:

What would happen if you stuffed the biggest piston in there u could get then added alot of weight to the crank and turbo'd the assembly. Wouldn't it launch like a rocket and have the momentum at shift points to carry on like one? It seems obvious torque is the quickest way to the finish line once again. Are we doing all wrong here? We already know these engines won't turn the rpm of newer desighns. Is the flywheel affect only for the Harley's? Why would the engine need time to spin up when the bike is revved before the clutch is engaged? Ok I hereby challenge anyone and everyone out there to cut this theory to PIECES. To me it's all about how can one make the wheel turn harder. More weight in motion vs more motion. I don't think the answer is taking an itty bitty motor to 20,000 then only having to squeeze the crank between your fingers to stop it instantly.

And don't forget the nitrous! And a redline for chrissake!

nads.com wrote:

What would happen if you stuffed the biggest piston in there u could get then added alot of weight to the crank and turbo'd the assembly. Wouldn't it launch like a rocket and have the momentum at shift points to carry on like one? It seems obvious torque is the quickest way to the finish line once again. Are we doing all wrong here? We already know these engines won't turn the rpm of newer desighns. Is the flywheel affect only for the Harley's? Why would the engine need time to spin up when the bike is revved before the clutch is engaged? Ok I hereby challenge anyone and everyone out there to cut this theory to PIECES. To me it's all about how can one make the wheel turn harder. More weight in motion vs more motion. I don't think the answer is taking an itty bitty motor to 20,000 then only having to squeeze the crank between your fingers to stop it instantly.

big bore/light crankshaft and a heavy ass rear wheel

U did say u wanted this to be reliable didn’t u? Keep that word in mind.
As u chase more rpm u will loose that trait.
There are many reasons, that have be mentioned that deter the kz from high rpms.

Higher rpm = less time for cyl to fill= larger valves and taller lift= Valve float.= need stronger springs, then they need to be replace more often. Big lift kz 1000 springs only last 20 passes at the track.
Bigger bore shorter stroke= more stress on con rod.
Bigger bore , and more rpm = less time for flame to travel across cyl= detonation= race gas.

But in the end , they all spell LESS RELIABLE.
Just a few road blocks. The road blocks don’t stop us from higher rpm’s but they do stop the motor from being reliable.
I’m am not knocking u , just adding to your wisdom.