engine harm from high RPM

[250X_project]

I know that high RPM's of course can cause an engine to blow. Broken rod, floating valves ect. Now if none of this happens, does this actually mean that no damage has occurred? Wouldn't the high R's harm the valves, by slamming them down onto the seats? Just another question I've wanted answered for a while. Thanks.

[400eXr1d3rZ]

Keep WOT on long roads or something is bad. If you stay at WOT for a long time.

[†2005 400ex†]

Originally posted by 400eXr1d3rZ
Keep WOT on long roads or something is bad. If you stay at WOT for a long time.


Exactly, an engine is perfectly fine at higher rpms for short periods of time, when you hold the high rpms out for a prolonged period of time..........not good

[250X_project]

When it stays wide open for extended periods of time, what damages? Do the rings just wear faster or does it just put more stress on the rod, pin, valves, and pretty much everything? Give up the details. Thanks

[†2005 400ex†]

It puts excess strain on the rod, valve train basically everything in the motor.

[400exrider707]

Theoretically it shouldn't make a difference. Everything moves the same no matter how fast up and down its going. I think the extreme heat from running WOT alot is probably the worst thing for it, provided of course your not floating valves etc.

[Wheelie]

No-load high rpm is bad for an engine. Example--riding in first gear against the rev limiter for a long period of time.

[Blue250X]

I would think it would be worse for it at high RPMs because the piston is getting thrown down with more force then shoved right back up. I think that would be harder on the rod because its like throwing a ball with a rope tied to it straight down and then pulling it back up or just dropping it and picking it back up. I dunno just a thought.

[400exrider707]

Originally posted by Blue250X
I would think it would be worse for it at high RPMs because the piston is getting thrown down with more force then shoved right back up. I think that would be harder on the rod because its like throwing a ball with a rope tied to it straight down and then pulling it back up or just dropping it and picking it back up. I dunno just a thought.


Its not really like that though. The crank is revolving, not going up and down, I realize the piston is, but all that force is being transferred into rotational force.

Originally posted by 250X_project
When it stays wide open for extended periods of time, what damages? Do the rings just wear faster or does it just put more stress on the rod, pin, valves, and pretty much everything? Give up the details. Thanks

Rings do wear faster. If you have 1 400ex that you run only at 5000 rpm and a nother 400ex that you race with in high rpm the one thats in teh high rpm will need rings sooner only cause more friction from the piston going up and down more.

[†2005 400ex†]

revving an engine under load to high rpms isnt as bad as just revving it with no load, when there is no load on the engine the centrificle force made by the piston and the rod revolving the crankshaft is more un balanced if you get what im saying, its harder for the engine to control because the rev is more uncontrolable

[Blue250X]

Originally posted by 400exrider707
Its not really like that though. The crank is revolving, not going up and down, I realize the piston is, but all that force is being transferred into rotational force.


OH! ok I see it now, it makes more sense. Thanks.

[250X_project]

Originally posted by LTD
Rings do wear faster. If you have 1 400ex that you run only at 5000 rpm and a nother 400ex that you race with in high rpm the one thats in teh high rpm will need rings sooner only cause more friction from the piston going up and down more.

I like that. That is true. It makes me think of my buddies 440EX that had less than a yr on the engine, but was a hard portion of a yr. It burned oil when sold. My 250X, had the same rings for AT LEAST 4yrs (just sense my freind owned it, could have been original from 92). Thanks everyone.

[400exstud]

Originally posted by †2005 400ex†
revving an engine under load to high rpms isnt as bad as just revving it with no load, when there is no load on the engine the centrificle force made by the piston and the rod revolving the crankshaft is more un balanced if you get what im saying, its harder for the engine to control because the rev is more uncontrolable

There is no such thing as centrifugal force.

[81 clark racing]

anyone no how much it cost to replace the rings and all that stuff when your rings burn up? like lets say a 406 or 416 bore how much would that cost and ruffly how much time involed in doing that. thanxs

[PismoLocal]

A piston kit is usually around $100.

[250X_project]

Originally posted by 400exstud
There is no such thing as centrifugal force.

You, at the very least need to buy a dictionary. I once saw a post w/ a reply to a quote being, think before you post... You may want to try that next time...

A piston can be found at about $85 shipped off eBay, less if you find the right auction. Rings only, should never be more than $30. It really doesn't take too long. Once the plastics and gas tank is off, it goes fast. Head cover, head, and jug are next. Replace what you are replacing, then put it all back together.
Oil and lube things while in the process and break it in properly. ;)

[400exstud]

You need, at the very least, to take a physics class.;)

Tell me, then, where does this centrifugal, or "center-fleeing", force come from?

[Def-e-nition]

Explain .

[bwamos]

Originally posted by 400exstud
You need, at the very least, to take a physics class.;)

Tell me, then, where does this centrifugal, or "center-fleeing", force come from?

Easy.. an object in motion tends to stay in motion.

A moving object always travels in a straight line unless another force is applied to it.

Rotating.. say a wheel or a crankshaft.. the material in motion want's to stay in motion traveling in a straight line.. therefore a centripetal force (center tend towards) is required to keep the mass rotating in a circular motion. (every action has an equal and opposite reaction).

The centrifugal force is the force that the mass has when trying to continue in a straight line (wich moves away from center). centripetal force is the force required to act against that force to force it back to center usually a combination of molecular bond and mechanical input.

Centrifugal force is a reactive force. Applied force is centripetal.

--------

That being said.. load vs. no load on the engine doesn't increase centrifugal force, it unbalances it because the crank/rod/piston combo is balanced against the load coming from the transmission/wheels moving the atv forward. Aka.. parts are pulling when they should be pushing.

It's like riding on your quad with blown shocks & good springs.

[250exkid]

yea basically to sum it up the high RPM's make you motor run hotter witch resultz in your rings burning up and after that you can blow ur engin!

[250exkid]

who keeps on saying theres no such thing as centrifugal force??? im in 10th grade and in 9th grade SCIENCE CLASS we had tests on that force stuff so bwamos hit that one on the head with explaining it

[400exstud]

Originally posted by bwamos
Easy.. an object in motion tends to stay in motion.

A moving object always travels in a straight line unless another force is applied to it.

Rotating.. say a wheel or a crankshaft.. the material in motion want's to stay in motion traveling in a straight line.. therefore a centripetal force (center tend towards) is required to keep the mass rotating in a circular motion. (every action has an equal and opposite reaction).

The centrifugal force is the force that the mass has when trying to continue in a straight line (wich moves away from center). centripetal force is the force required to act against that force to force it back to center usually a combination of molecular bond and mechanical input.

Centrifugal force is a reactive force. Applied force is centripetal.

--------

That being said.. load vs. no load on the engine doesn't increase centrifugal force, it unbalances it because the crank/rod/piston combo is balanced against the load coming from the transmission/wheels moving the atv forward. Aka.. parts are pulling when they should be pushing.

It's like riding on your quad with blown shocks & good springs.

You are correct about the centripital force. There is no force that causes an object to be "center fleeing." There is inertia which causes it to continue in a linear path at a constant rate until reacted on my a net force. This is the only reason why a ball on a string would keep flying after you let it go. It doesn't go away from you, the center, as in a centrifugal force says; it continues in a linear path from the point it was released.

Where's GPracer?

[400exstud]

Originally posted by 250exkid
who keeps on saying theres no such thing as centrifugal force??? im in 10th grade and in 9th grade SCIENCE CLASS we had tests on that force stuff so bwamos hit that one on the head with explaining it

Your out of your league and don't know what your talking about.

AP Chemistry and Accelerated Physics this year

AP Physics next year

[400exstud]

bwamos

This is what a centrifugal force is (CENTER fleeing). I know that you know that this is not how things happen in nature.

The straight line is inertia's affect on an object. This what happens.

[250exkid]

right i forgot ur better then every one and im just out of ur leagie im sry i ever said anything lol wow:grr:

[2muchquad]

You guys have too much time on your hands.:D Sounds like 2 ways of saying the same thing to me.:D

[400exstud]

Originally posted by 250exkid
right i forgot ur better then every one and im just out of ur leagie im sry i ever said anything lol wow:grr:

Don't take it personally; however, you do not know what you are talking about.

[BigValvedEX]

most people on an ATV site will talk about badass quads, but in this case we got dweebs talking about **** they had in high school. hmm where is my pocket protector

[250X_project]

LMAO. The centrifugal force of the crank is the entire point of an engine.. there's just no way around that.

[Toadz400]

Where's Wilkin?

[250X_project]

Yeah, I hoping for insight from GPracer2500 and Wilkins250R when I posted this.

[400exstud]

Originally posted by 250X_project
Yeah, I hoping for insight from GPracer2500 and Wilkins250R when I posted this.

Me too. I haven't seen either of them in a while.

[400exstud]

Originally posted by BigValvedEX
most people on an ATV site will talk about badass quads, but in this case we got dweebs talking about **** they had in high school. hmm where is my pocket protector

LMAO! Good one:rolleyes:

[wilkin250r]

Originally posted by Toadz400
Where's Wilkin?

Wilkin has been busy.


There are two main dangers with high-rpms. The first was already mentioned, breaking the rod or piston, floating a valve, ect. The second is additional heat, possibly causing a seizure or other problems.

However, ask yourself this question. Why are you more likely to break a rod or piston? Because high-rpms created higher stress.

The definition of inertia is: "Resistance or disinclination to motion, action, or change". When the piston is traveling upwards, it has inertia. It wants to continue upwards, and it pulls on the connecting rod to get it to stop. Tie a brick to a rope, and tie the other end to your foot. Throw that brick off a bridge, and you'll get an idea of that inertia.

The faster the piston is moving, the more stress it creates to get it to stop and reverse direction. When the piston is traveling upwards, it pulls in the rod, which pulls the crank, which pulls against the bearings and the cases. All this stress is MUCH greater at high RPMs.

Higher RPMs will cause your bearings to wear out faster, your crank to wear out, tiny stress cracks in your cases (which can turn to BIG stress cracks) and so forth. It will age your engine much faster, and things will break sooner.

Oddly enough, the rings aren't a big issue. Sure, running at 10,000 rpms will wear out the rings twice as fast as 5000 rpms, but that's just because it's the same overall number of strokes, it's a linear relationship. The other factors in your engine are not. Running 10k rpms will wear out your crank and rod TEN TIMES faster than 5k rpms.

[Blue250X]

Originally posted by 2muchquad
You guys have too much time on your hands.:D Sounds like 2 ways of saying the same thing to me.:D

I skip posts with too many big words in 'em.:macho

[250X_project]

Originally posted by wilkin250r

Sure, running at 10,000 rpms will wear out the rings twice as fast as 5000 rpms, but that's just because it's the same overall number of strokes

You took the words out of my mouth on that one. Thanks for the input. I think that was the best post in here. At the same time I posted this post, I also did one on cold weather running. What is your input on that? Is the cold weather worse for an engine? Is oil flow restricted? Thanks!

[wilkin250r]

Originally posted by 250X_project
At the same time I posted this post, I also did one on cold weather running. What is your input on that? Is the cold weather worse for an engine? Is oil flow restricted? Thanks!

I've been offline for a couple weeks. I did a search for my name when I came back on the other day, and that's how I found this thread, but I didn't see any others.

If you want to find the thread and bump it up, I'll give you my input on it.

[400eXr1d3rZ]

Originally posted by 250X_project
You took the words out of my mouth on that one. Thanks for the input. I think that was the best post in here. At the same time I posted this post, I also did one on cold weather running. What is your input on that? Is the cold weather worse for an engine? Is oil flow restricted? Thanks!

Different oil weights work differently in different (hmm i said that alot) weather conditions. The only way cold weather would harm your engine is if you didn't rejet for it.