Maxed Out RPMs: Problem??

[motoholic]

Hey all!

I was getting on the highway today and was making sure I didn't get hit by the cars next to and behind me and didn't watch my RPMs. I accidentally maxed out my RPMs in first gear. The only reason I know this is that there was a brief, sudden deceleration. It might be my imagination, but it seems like the engine is slightly sluggish now, even when in neutral and blipping the throttle. However, shifting is seemingly much smoother, now.

Anyone know if I might have done some damage or if there is some sort of inhibitor on the bike which might have caused some of the above symptoms? Any information would be greatly appreciated as I don't own a car and this is my only way to get around.

Thanks!

[FzPilot]

Unless your bike is in it's very early brake-in stage (and I mean very very early) you have nothing to worry about.

You felt deceleration because you've ran the RPMs to it's rev limiter, that is actually there to protect your engine from over-revving.


Cheers,

[motoholic]

That's what I figured. Just wanted to make sure, though. Thanks again!

[Guitar Man]

I think you will be OK. If you pegged it off the rev limiter as soon as you started it up I would think that is the senario that would cause the most damage.

[DefyInertia]

Dude, I've done it a hundred times...it's all good. Just don't blow past 14K on downshifts as there is no rev limiter to save you there...purely mechanical.

[rsw81]

Believe it or not, bouncing off the rev-limiter is incredibly bad for the valve train of any engine. It is there to prevent you from over revving the engine which can cause the valves to float, due to inferior valve spring ratings to engine speed. Bouncing off the rev limiter causes sudden changes in engine rpm which is almost just as bad as it puts a lot of strain on the valve train to sudden change speeds like that, instead of the normal gradual change in speed.
If you did any damage, you'd know it 'cause the bike would really run like crap. You'd get poor compression, and thus poor combustion. If the bike generally feels like it is running alright, I wouldn't worry about it. Doing this once in a while will not likely do any damage, but I wouldn't make a habit of it.

[DefyInertia]

Originally Posted by rsw81

Believe it or not, bouncing off the rev-limiter is incredibly bad for the valve train of any engine. It is there to prevent you from over revving the engine which can cause the valves to float, due to inferior valve spring ratings to engine speed. Bouncing off the rev limiter causes sudden changes in engine rpm which is almost just as bad as it puts a lot of strain on the valve train to sudden change speeds like that, instead of the normal gradual change in speed.

It's a 600cc I4, not a tuned to heaven vtec ricer. Do you realize how incredibly common bouncing off the rev limiter is (not that that prooves anything by itself)? And it does not cause significant "sudden changes". It's more like going from acceleration to 14, 14, 14, 14.

I would like to see some support for how this is "incredibly bad" for a modern sportbike. All it does is prevent you from gonig farther...it's not violent (revs, speed, chasis) at all.

EDIT - for some comic relief, all the squids around here greet each other by bouncing their engines off the rev limiter with the clutch pulled in...LOL!!

[rsw81]

Originally Posted by DefyInertia

It's a 600cc I4, not a tuned to heaven vtec ricer. Do you realize how incredibly common bouncing off the rev limiter is (not that that prooves anything by itself)? And it does not cause significant "sudden changes". It's more like going from acceleration to 14, 14, 14, 14.

I would like to see some support for how this is "incredibly bad" for a modern sportbike. All it does is prevent you from gonig farther...it's not violent (revs, speed, chasis) at all.

EDIT - for some comic relief, all the squids around here greet each other by bouncing their engines off the rev limiter with the clutch pulled in...LOL!!

Like you said, bouncing off the limiter with no resultant damage does not prove that it will not cause damage down the road if done repeatedly. I do not have a link of any proof of the damage that this does, but it is commonly known that bouncing off the rev limiter can and will cause connecting rods to compress, bend, and then break which of course leads to engine failure. This can also happen just from over-revving the engine as well. This is true of motorcycles, "tuned vtec rice rockets", american V8's, or any other engine that is not a rotary engine.

I don't think anyone on here needs proof that bouncing off the rev-limiter is a bad thing. If anyone is truly interested in knowing exactly why it is not recommended, I'll try harder to pull up articles on it for you.

[DefyInertia]

Originally Posted by rsw81

I don't think anyone on here needs proof that bouncing off the rev-limiter is a bad thing. If anyone is truly interested in knowing exactly why it is not recommended, I'll try harder to pull up articles on it for you.

Yes, please do. I've NEVER heard that before (not that that proves anything...lol)

[rsw81]

I can't find any reliable source of information, only forum threads about it. As such, take this information with a grain of salt, but it does make sense to me. If you know the inner workings of an engine, this will make sense.

1. Most people seem to say that bouncing off the rev limiter is fine.

2. Rev limiters are not entirely accurate and can allow engines to spin over the redline briefly, causing valves to risk float. This risks bending valve stems or even ejecting a rod through the block. (I find this one not very accurate as most engines are engineered to handle much more than the redline indicates)

3. The sudden change in acceleration/deceleration associated with bouncing off the rev limiter puts a lot of strain on the timing chain/belt. This can cause the chain to jump a tooth on the sprocket or cause the timing belt to slip a bit. This in turn causes the valve train to be improperly timed with the piston position --> piston hits valves --> bent valve stem, poor compression, bad combustion, etc. (This one makes the most sense to me given my knowledge of engine mechanics - I've been working on cars for ~15 years and they share the same basic mechanics with motorcycles)

In conclusion, I think it would be okay if it happens from time to time. No harm no foul. Repeated abuse in this regard I think will result in long term damage to the engine, specifically the valve train as mentioned in #3 above. For all we know, no damage will be caused in our engines. Only an engineer on the design team at Yamaha can give us a solid answer on this.