10k rev limit

[jacobw]

thanks 27 that kinda puts all the stuff in perspective I never knew about alot of that so I am a learnin:) :head:

[Derno24]

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It is funny to me when you say pro guys beat their machines harder. I have Rick Cecco's quad sitting in my garage he was a decent rider. Then there is Randy Brandt local, oh and Jeff Stoess. My proof is the hundreds of Dale's that are still running and mine too. I guess I don't matter as I am a trail rider. Although I hit 30 races last year and so did CDrookie. His ran with no fluid in it for most of the year too.

All you guys I have respect for what you are saying, and value opinions more than anyone.

[cannondale27]

Only problem with the testing was they stopped doing it and still made changes.

[HouserCannondale]

I dont see what all the hype is about a decompression mechanism failure... seems theres not nearly as many of those failing as crankshafts. ive raced my cannondale for a year and a half and had some other engine related problems but never a decomp. i guess all im tryin to figure out is why some people are saying that just because a decomp flew apart that the revlimiter is too high. and as far as using a lower revlimit for trail riders. thats pretty much a waste of time. in one sentance someone said that people who ride casually should lower their revlimiter to save the engine. if they ride casually whats the point to lower the revlimiter in the first place?? :confused: jeesh people.

[claas900]

...wistech..I wonder if that valve dropped cuzz the cam was taking a dump and hitting the valve causing damage,or when the cam was taking a dump and the valve bucket was grinding down caused it to stick open??
....Cam grinding down cuzz its to soft or not getting oil,and i think if it went getting oil wed know that right away? Also don't the Z bearing help with to much oil being lost at the rod,getting more to the head?
....Iv heard the rod bearing wasn't meant to be in something rotating its meant to be a "still" bearing?? And for the 10k or 11k limit on the rod bearing i think is false,I think when its used with grease its 10 or 11k but when in oil its like 14 or 15k i believe?

[timbomoose]

I'll be keping my rev limiter lower for now on,but can see the advantages of it ,by staying in the same gear before a corner where you would've had to shift before.I had valves blow off twice and trash everything with the high limiter and that is enough for me.Higher rev limiter WILL wear out everything faster.Every material has a fatigue point wheather it is steel,plastic, alum,etc the more stress you put at it the faster it will wear.Higher rpms will wear out cranks faster because of the higher the speed the faster the direction change and the more stress and heat put at the steel.The higher the engine revs the the more stress put on the cam guides from centrpical force of the chain against the guides,valves float and when close to the floating point springs fatigue and the floating point becomes lower and when valves float thats when damage can occur.Fact,the higher something is reved the faster it will wear (more distance traveled in the same amount of time- more wear).I agree with 27 the best thing is preventative maintance,when running on the edge replace parts before they are problems.If you do not need that little edge you can give yourself some more time inbetween by dropping the rev limiter down 500rpms.I' tried the 10,000 seem too low run 10,600 with heavier gearing never missed the limiter after that.

[cannondale27]

Since FX400 changes in head:
Different valves
Different Cams
Different seats
Different retainers
3 different decompression styles
2 or 3 different timing chain guide mounts
Never did figure out why when you put a new style cam in a old head you have to use huge shims.
Now I dont know at what point they stopped doing testing but I do know that the SSM case was not tested at all.So around then.Also keep in mind Dyno testing is not real world and we are well past the time in which they spent testing in real world conditions.The quad owners were the testers even back when they were in business.Many new problems surfaced when the quads came out.Most of the racers pro or ametuer like me had a new motor every season so now we are in uncharted territory since wear on parts accumulates.

[Jaybr]

QUOTE

Originally posted by Derno24
Just one question for you guys.  What parts have changed in the head since they came out with the fx400.  Just the head remember.

Not sure I even want to get into this thread since it's become such a mess.

Cams changed - early where made by Megacyle, later shipped to someone in Europe

Decompression changed - was billet steel, changed to a cheaper powdered metal of some sort.

Valves - I believe the early valves had a strait stem, later where tapered.

QUOTE

Originally posted by  bombsquad54
i know that too high of a rev will hurt a motor, its not good for it. nuff said

Sure that's common sense, but what contistitutes TOO high? There is no proof that 11,600 is too high.

I think I agree with both sides of this argument, depending on the motor. I believe early motor before cheaper parts where used are fine at 11,600. I also agree that Cannondale did extensive testing, and proved this rev limit was fine. I'm not sure they did the same testing after going cheaper on the parts, in fact I doubt it because of the expense and loss of budget.

Also keep in mind that those early motor before head changes also had balanced cranks.

Is 11,600 too high for motors with the cheaper cams and decompression mechanisms? I don't know! I do believe that the cheaper cams wear faster, and that the powder metal decompression mechanisms will shatter, but not sure what causes that.

As far as valve springs go, I also know that many of them do not test out at the reccomended 40psi. I have some upgraded valve springs in my head that are 43-44 psi and are 1mm longer, when the motor gets back together I'll provide some test results.

[Derno24]

Thank you guys. I think we are back on the road to being informaive again.

Timbo: On the heads that dropped a valve were they completely stock or did they have any work done to them? I ask cause one of the head I have seen eat it was worked.

[cannondale27]

I am still not convinced that other than the decompression and some soft cams that our valvetrains are any worse than any others out there.In fact I think they may be a little better.Improvements can be made for sure and I understand pefectly why some will lower their limit to be safe.But replacing parts before they fail will also work.I hope.