RPM vs. Motor life.

[weimedog]

Here's a general question...kinda of interested in what you all think:

If a motor makes its power say at 5000-7000rpm and therefor is ridden usually at those RPM's will it last longer than a motor that makes it's HP at over 10,000 and therefore is used at those RPM's.

Part of the assumption is that they are both over square therefor have reasonable piston speed at any RPM. Also they have compression rations close to each other.


What about clutch life? (low rpm motor vs. high rpm motor)

What about time between oil changes?

What about ability to handle long high speed events like desert races?

Is the motor wear usually at startup? So RPM's are not a factor?

Any thoughts?:)

 

[chadk01]

High RPM=New Top End
Low RPM=New Spark Plug.

On a serious note, I'll let someone else respond to this. As you can see, my knowledge base will not allow me to expound on your question.

:o :o

 

[cujet]

Interesting to think about. The BMEP goes up at lower RPM and therefore there may be more stress on certain components such as piston rings. Higher pressure loads the rings against the bore, however, con rod bearings see more stress at higher revs, as the inertia loads the bearings. Valves and such see higher stress at higher revs.

I believe the answer is that generally higher revs result in shorter engine life. However, load is a big factor also.

In the distant past, there were a few motorcycle engines that were made in 1, 2 and 4 cylinder versions. The 124cc 1 cyl versions always had a short life, the multi's lasted much longer. I believe this was due to overall engine load. The multi's did not need to have large throttle openings or high revs to achieve the necessary output.

Chris

 

[spanky250]

Something to think about: 125s rev much higher than 250s, and they need rebuilds much more often.

 

[weimedog]

Something to consider when trying to figure the cost of ownership over time is my bet. ...

 

[jmics19067]

I would think that a start up after the bike has set would be worse on a four stroke. Having to wait for the the oil to circulate. The two stroke having the oil in the fuel, is right there when it fires up.Still dont mean that you shouldn't warm it up or that you won't be replacing pistons a lot quicker in a two stroke. <sorry about the double negatives but I think I meant what I said>

high rpm screamer more clutch problems . having to feather the clutch more to get going than a motor with lots of low end torque