how to raise max RPM's

TexasKZ wrote: "Horsepower is basically a mathematical relationship between torque and engine speed (rpm)."

Here's a calculator that might be fun to try:

Calculator

with your rod combo that your buying about the only limiting factor would be piston speed the stock rods will stretch in fact i have and old 810 alcohol motor laying under my bench right now that when you measure deck s it was about .003" under which should be good plus a .40" head a gasket yet the rods or bolts stretched enough that all 4 piston's hit the head and hard enough to collapse the ring lands i know this motor and how it was used it spun at 12,000 rpm on a regular basis and it never hurt anything but my buddy cranked up his shift light to 13500 rpm and then the pistons hit the head.game over for that bottom end also we noticed after we tore the engine down that the cam bores and bearing surfaces on the cam where galled up very badly so we are kindof thinking at that kind of rpm the oil film on the cams was being flung off and the cams where starting to stave for oil. another consideration of what may happen with ultra high rpm's . this damage did not occur the first time he went higher rpm but it wasn't long and before that the motor was bullet proof it 10.10 all the time but he cranked up the rpm to try to get the elusive 9 sec pass and wrecked the motor. he should of been happy with the 10 sec. passes.

I guess I don't get this tread at all...

Is this about building a realistic 810 motor from a 650 base engine or what?

In a "Nutshell" here's the basics to engine building. But it's gong to be long with other reasoning.

There are 3 ways you increase the output of the engine.

1. Make it Bigger

2. Spin it Faster

3. Make it more efficient

The "redline" is generally considered to be the rpm range where you're beginning to spin the engine beyond safe mechanical limits.

1. Is a no brainer.. Bore & Stroke.

2. Is more complex from several aspects. You can't spin it faster if:

a] The piston demand for air can't be delivered
b] Mechanical failures, rods, bearings, etc. [See Timebomb's post on the stretched rods]

3. Increasing efficiency can be a either or a combination of breathing efficiency, combustion efficiency [compression ratio] or mechanical efficiency [friction reduction]

All of those three methods overlap. For example if you stroke it, what happens to your piston speed? Think about it.

So the first place you start with a motor that you're going to do a performance build on is to look at the reliability factor of piston speed.

How fast can you reliably spin the motor.

Now, you have to look at the feasability of feeding the piston demand at the Peak HP RPM you can reliably run the motor.

That's where the cams, valve size and CFM come into the picture. The curtain area plays heavily into wheather or not you will be able to feed the engine at the new, higher RPM.

Valve size, cam lift & duration all play into that formula.

This speaks nothing of sorting out "how" the power delivery will be. The cams & carbs /TB size rule the roost in that department.

In situations where you cannot go larger on valve size, then more cam duration can help you meet the curtain area requirement for the higher RPM.

With every option you select as you calculate your way through, there are drawbacks. Eg. Bigger valves may be required to establish the curtain area. Great...except now you have clearance issues to contend with. Valve to valve and valve to piston clearances....

Higher lift camshaft bring their short coming to the party. Now you have guide clearances, tappet bore clearances, tappet diameter..to name a few.. to factor in.

So there you go. You said you want to build an 810 motor that will do around 90HP at the rear wheel and live. Go back to the previous post where the components that will allow you to get there are all laid out.

Heed the advice everyone so kindly offered regarding excessive RPM and you're off to a good start. RPM is great. It absolutely rules when it comes to producing maximum HP. But everything has to be designed to withstand it.

Modern sport bike engines keep climbing in peak RPM. They pretty much have nowhere else to go to keep producing more power and maintain current class sizes.

Then look at say the big S&S motors. They figured out that if you make it real big, you can produce lots of torqe down lown in RPM and the thing will last.

Another benefit of making it big is it allows you to get away with more cam and carburetor without loosing the bottom end performance.

The down side to making something really big is you can run into breathing efficiency issues if you can't get a cylinderhead to feed it.

And Plumen nailed it right on the money. How many of those 14000RPM motors do you think will be kicking around 30 years down the road? They're throw away junk. A flash in the pan.....It's been that way since that late 80's for the most part..

A lot of the guys on here have been at this for many yeas now. Plumen & Timebomb just to name a couple more. When they lay down advice, it came from experience in blowing things up and makeing things work. Both are part of the game. They're just trying to keep your wallet from going on a diet....

Larry C

As a purely Theoretical conversation, I'll offer these, (most aleady mentioned) stock redlines on era machines have been limited by different limitations. IE. Points float, valve float, the ability to flow/process air/fuel mix, and then, my contribution:Sorrily enough,I'm too lazy to research the #'s, But, Gynormous forces are developed by accelerating and decelerating a piston at high revs. (consider, with each revolution of crank, the piston/rod comes to a stop and reverses direction twice.) some of the distances previously mentioned are due to the dissappearance of the oil cushion present at bearings.Thus current high reving engines running shorter lighter slugs, and relitivly large bearing diameters. Regardless, on many current engines, redline is determined by the the strength of connecting rods and their abilility to handle these acceleration/decelerations. G

if you really want to build a reliable 650 based motor thats capable of making 90/100hp when needed its very easy.start with the best possible bottem end you can build including those carillo rods,id still have those rods checked including magnafluxing and new bolts at minimum.if anything looks questionable in there change it! id go with a reasonable street compression set of 810 pistons and a gpz style head as Larry said,with a STREETABLE set of cams and some carbs in the area of 29mm or fuel injection if you can swing it.im guessing this should put you in the 75-80 hp area with a motor that can be ridden without having to constantly tweak things on it,once you get it running the way you want then you can put a small nitrous bottle on it witha 20hp shot for those moments you really feel the need for it i think youd be much happier with that combination than a peaky buzz bomber that makes its power from 8000-12000rpm.oh wait kawasaki made one of those,it was called the H2 750 triple 2 smoker! :woohoo:

buy a used cbr 600rr or yzf 600r or zx6r or gsxr600 and it'll cost you less .....then you'll have an awesome reliable kz if you leave it mellow ,and,...... a high rpm 100 horse power wind up bike......considering modern 600 sport bikes cost 2500-3000 used and can run those numbers with stock exhuast and pump gas and have been for about ten years now........try spending 2500 on a kz and see how many miles you get before it fails.....over and over on here folks talk about pumping up the engine....and half the bikes don't even run..... half the time....the KING has no clothes!!!!! there i said it!!!!!!


turn key high rpm.....


or you can put a chevy 350 in a pinto...same idea...

If you want to rev high two stroke is the ticket. But two stroke bikes will need a top end as soon as you rebuild the top end. Kinda like changing the oil.

....... my 33 yr old engine...never been opened up and runs good and good enough for me and the other citzens on the road with me....gets comments everywhere i go and that's cause it runs to go all those places all the timne and takes me along for kicks too .....so i can ride it everywhere year after year after year.........watch e-bay and see all the p.o.s that are "punched out"... or "rebuilt".....does'nt run but just needs...yada yada yada.........i guees the folks who designed my stock motor three decades back to be as it still is todayin this world of 200 hp motorbikes and bullit proof knew some stuff too......go figure,,,,,tear it down bench racers are a dime a dozen....then they kick start their bike and it won't play the tune........folks who say get a zx6 and leave your bike be!! are smarter than you give em credit....believe me:woohoo: ...better yet tear into your kz....you'll be singing a different song come next spring :blush: and i'll be riding my same bike....somthing to consider...just cause everyone gets a tribal tatoo don't make it cool.....imo....hardr0ck68 wrote:

If I wanted to buy a zx6, or an R6 or a cbr600 I would own one now...and be blissfully ignorant about what it takes to make an engine work and work well.


You folks never get on a gpz1100 guys telling them to just buy a busa, or zx1400 and not bother with adding a turbo or NOS.


Yeah it will be questionable if it will still be a kz650, but it will be MY bike.

I really miss Steell cause that guy knew stuff other than "buy a new bike"

I beat my 1015 bike so bad; Water boarding is like ballet in comparison. Every time I miss a shift at an ungodly rpm, the parts just settle in better. I come zingin by a 600 like it's standin still at 100mph, and I was even FAT then at 250lbs. Havn't driven for 2 years but that's not the reason I lost the damn license. I went for 3years without one and there's not a county road or country highway that hasn't been burned up around Fargo ND because of it. But I had the same damn problem over and over again. I kept running out of GASS! Next april I'll be rockin again. DON't ever listen to anything anyone says that's negative. Do it on knowledge, do it on intinct. And KICK SOMEBODY'S ASS! You've been given the knowledge to build exactly what your looking for. Cut through the crap with a smile and a wink and march on. Them old guys now remember were brought up when cell phones were as big as air matresses, black and white tv's were a commodity, and you still drug your wife around by the hair. And graduations were the little marks on a glass container that scientists use. G.E.D was the words used by fedral agents when they came for their property after looking around their garage. GOD! EVERYTHING'S DAMAGED! so they take the hammer collection and all the cold chisle's. Never realizing all they'd needed was to take the scrap metal, melt it down and it'd be even up. Can someone say a,bc,d,efe... That's all for me. OH yeah, got a vision of jumping up and down on the cell phone buttons ordering parts. Fashoning a beer top opener. #days 3 cleaning silicone off shoes 1day, hangover 24/7, open bottom drawer tool box, ahh pizza, second drawer rolaids, camels, shooter, hustler. Panties? Now where the hell that screw driver go? Mise well mix another one, ice ed be melted in it anyway. Bad day? spilled piss bucket on boots, started fire in garbage can, garagee door came off track, best buddy drank all the beer, still sleepin in your bed. Positives? Excuse to buy new boots, good reason for beer/bar run, cool breeze in garage, wifes in a good mood.

Nads... I have no idea what the hell you just wrote. :blink: :laugh:

OK, another forum I'm on has something of interest for you.... This is one killer KZ650 and it tops out @ 10Krpm...

Here's some information for you on this serious build, some of the results and what you can expect in what your asking for.... $$$$$$$$$$$$$ :huh: :dry: $$$$$$$$$$$$

Here are some stats - 831cc mechanical fuel injection on alcohol
14:1 static compression
50-52 deg ignition lead
Mallory sprint mag
Hilborn 00 pump
one gallon fuel cell (stock tank is a dummy)
5.5" Goodyear slick
3" over stock swingarm
lowered front and rear
hydraulic clutch
lockup clutch
MRE airshifte

Quotes:
I have not been to the dyno for a long time... I will tell you that number was 122hp in 4th at 10,000.

I cant comment on the RPM as this was a big discussion years ago until my buddy saw those print outs... the motor I have built drops right off after 10,000 so there is no use in going past that - it has seen a bit more, probably 12,000 but there is no way these motors make power past that point.

As far as torque I remember that being a very flat line just like a street motor... nothing special, torque was about 52ft lbs across the board at about 7,000.

I have 25 years of development into my motor and at least
+$10K into the bike (don't know how much is motor) which I consider to be cheap since my buddy does the majority of my machining - paid for in homebrew !


In all seriousness, as the others have been informing you of, what your asking for is just not going to happen... Not easily nor cheaply and even if you could, it would no way be a daily driven street bike....

Hope this helps

OMR

If there is no more power to be had at that RPM then I have no real interest going there. This thread was started along time ago and I just want to get as much information as possible before building my motor.

As I have stated before, I was under the belief that small displacement 4 cylinder motors made power via high revs.


My next question is why does the power drop at 10,000? Just not a way to get the charge into the cylinders in time? Or is there something more than that... could a turbo set with a long lag time and low boost (4 or 5 psi) be set to "turn on" at the right rev range and then stuff the intake charge in....


by the way, my budget is set only by time (and I am only 28, so I have years to dick with this bike) and hp... If I have to drop 5g on a mr. turbo kit to get from 90hp to 100... then such is life, they take Visa right?? That might be the only part I fit to the bike for 3 years, but as I stated I am young.

a good freind of mine who by the way is an instructor at the same college as me has a gs 750 two valver 1978 i think that runs on a alcohol and has an out of the box mr.turbo system on it and i personally have seen 240 horse on a chassis dyno dam impressive little bike with a 650 set up on gas i wouldn't be suprised if you could between 180 and 200 horse with a turbo and still have a fun civilized ride most of the other time and with the boost contrls that are around now it could be totally streetable.by the way the only thing that can stop a motor from producing power at higher rpm besides phyisacal limitations would be airflow.