10k rev limit

[Derno24]

QUOTE

Originally posted by Happyboy
No, ya beer guzzleing hippee!  :)  I don't think that the higher rpms are the absolute reason for our failures but at the same time I do think it contributes to our problems.  I am shooting for a high 10,800-11k rpm limiter.  Look at it this way, the faster you rev the more wear you will give to the crank bearing, the valves, valve springs,etc....  When the springs do fatigue you are more apt to valve float especially at high rpms.   Normally when we talk about high rpms the community (not us) jokes about 10k rpms.  Now we add almost 2k rpms to that.  Man, our motors are freaking monsters.  That is just one way I am going to tame mine.  And you know what, I won't miss 500 rpms.

Happy first of all these motors were designed with the Cannibal map at 10,600 so you suggest to take it lower. Now 11,600 is the moto, blaze, and speed #'s. If you are right, which you aren't then the 3 quads I have owned the 1/2 dozen I have personal experience with and the many others out there with 11,600 are all falling apart. Now I am not adding 2k I am adding 1k and it is stock mapping. Jeff is right about the custom built maps I think they should be aproached with caution, but spreading fear is just retarded.

No have a beer for me while I change my kids diaper! :drink:

[HouserCannondale]

the rev limiter is not susposed to be used as a shift point... its only there as a safety so that if you over rev or miss a shift your engine will not destroy its self. you should be shifting no later than 11k because after that you arent making a significant amount more power. with tougher valves and stiffer springs the engines will last alot longer. end of story. the engine life reflects on how you ride it. the harder you ride it and the higher the rpm range, the shorter the valvetrain life. simple as that. valves and vavle springs have to be replaced periodicly like anything else. its not like were talking about a 400ex or something thats designed to be reliable and run for a long time without being rebuilt. we have a race motor straight from the factory so it has to be treated as a race motor.

[cannondale27]

Yes Derno I agree it would be a real shame to lower the rev limit out of fear.We may even have a better valvetrain than the rest.
Now as far as the abuse on valvetrain quad /bike it is the quad for sure.The key to longevity in the valvetrain is clean air and keeping the valves from floating.The lighter the valve the easier it is to control float.I bet the valves in most streetbikes are Titanium they are all shorter in length than ours and alot are smaller dia.We run in alot of dirt and dust some of it gets in there.Ti valves are nice but dirt will wipe out the coating on them and then they will wear very fast.The valvesprings also are a major cause of float.The vibration of the spring under tension is a major cause of valve float and spring failure Yes a unbalanced crank could even be a factor in this but shock to the motor is also a big factor those shocks like whoops,bad landings,downshifts are absorbed by four cylinders in a bike rather than just one.Another factor is our little motor is pushing around a machine that weighs just as much or even more than most of the streetbikes.Add mud and the greater potential for overheating since less air is moving at our speeds.Quads valvetrain is abused more.One question for the bike guys.Why does it seem that the more cylinders a bike motor has the higher the redline is?

[banzairx7]

You make a good point with the smaller valves. Since each cylinder is half or less than that of ours the valves and hence the valve train can be much smaller/lighter. Since it's the weight of the parts that really matters with high rpm use the lighter these parts are the longer they should last.

[aroracer72]

Every racer i know hits his rev limiter...and if they dont..then they arnt fast/hard riders(mx'ers). The fact is..the higher you rev your motor...the faster its gonna go. Who ever said revving to the limiter doesnt produce mroe power/speed was wrong. By revving a motor instead of shifting up..you can jsut hit the break for a tight corner..instead of having to downshift and brake. By revving it allows you to approach a corner mroe simplier and usually faster. As for reliability..instead of lowering the rev limiter..those worried should remap for a lower end and mid end map and take away a tooth or two on the rear...this will allow you to go faster with less revs. It takes some tuning but you can get the same power and speed out of our bikes with less revs. But in ANY instance i will never lower my rev limiter..cause i ring the crap out of my engines and those extra revs means faster for me. We desperately need new springs and valves though..i agree with that. And cannondale made the rev limit that high..cause thats what they tested and found out they could use.
CHAD

[Happyboy]

QUOTE

Originally posted by aroracer72
And cannondale made the rev limit that high..cause thats what they tested and found out they could use.
CHAD

Why do people keep saying this?

1) If cannondale had tested and found this to work then why are there so many failures? Bad testing? Changes without testing? No testing? Who knows. But the fact of the matter is is that the valvetrain for one can't handle extended rpms in that range. They need an upgrade.

2) For racing--real racing--yes, you want the higher revs so you can squeeze everything out of the motor you can. But why do you stay on the limiter? Because of power or because when you come out of a turn you don't want to shift? Can't be for the power, there isn't any more left.

3)But the normal joe doens't need that. Racers know that they will need to rework the motor constantly to keep it running at peak performance.
The average joe just wants their quad to hold together longer. Staying off the rev limiter would help that. Hence lowering the rev limiter just a bit and then they can hit it without worrying.


Just my opinion. Revs do contibute to the bad things happening in the motor. Either you agree with that or you don't. If you don't then your wrong! Just kidding. All opinions....blah blah.

[wanablaze]

Chad,

Have you ever seen a dyno chart? At a certain RPM range, most motors make a peak torque and at another range peak Hp. After this RPM range, they make less power. Thus it can be ideal to ride in the power rather than at the rev limiter. For instance, if you drag race a modded blaster (Headpipe, silencer, reeds, etc) against a stock blaster, you will notice that it is better to shift early. A stock blaster motor only rev's so high. If you shift at this rpm range on both bikes, the modified one will win. Now try it again and let the modified bike wind out as high as it will. The stock blaster will be right next to you.

I chose a blaster because of the small hp differences and previous experiences.:w:

[cdrookie]

[QUOTE]Originally posted by Happyboy
[B]Why do people keep saying this?

1) If cannondale had tested and found this to work then why are there so many failures? Bad testing? Changes without testing? No testing? Who knows. But the fact of the matter is is that the valvetrain for one can't handle extended rpms in that range. They need an upgrade.



happy, happy, happy... cannondale didn't pull 11, 600 out of a hat. i'd bet they blew up plenty of engines at some serious rpm's before they decided that 11,600 was a good, safe rev limit.
it's kind of like suzuki's z400... they spent years and how much $$$$ designing and researching their flagship sport machine. but, even in the hands of recreational riders, their frames broke. every manufacturer has problems with their machines. quality control wasn't high on the priority list at cannondale, but that doesn't mean they didn't do the research.

[banzairx7]

I could see holding a gear against the rev limiter during a race. In autocrossing this is pretty common practice. The drop in power is offset by the time it would take to shift that gear. You end up just staying on the rev limiter for 10 feet to gain a fraction of a second.

[aroracer72]

i meant revving the engine farther is faster then nort revving...by this i mean......when you rev a gear farther...your quad goes faster...so revving benefits in speed...but hurts in reliability.....
CHAD