What does it do to the bike when you lug the engine?

 

I could be completely wrong here or miss some things but it is definitely hard on your clutch and can make your clutch start slipping prematurely and I would think that it can cause you to foul plugs and give you alot of carbon build up.

 

Lugging the engine makes the lower end bearings unhappy.

 

I'm not a mechanic, but logically it would seem that lugging puts a lot of strain on all engine parts especially bearings. Because when you lug you're getting power mostly from the combustion and NOT the perpetual motion of the engine mainly the crankshaft. Just my 2 yen...

 

Is it equally as bad to shift gears at higher rpms?

 

We can do a virtual experiment to show how forces can act on the bearings, lifters, and pushrod surfaces. Pretend that we put our foot out and a car runs over the toe really fast. Now imagine the car running over the toe slowly. Slow is much worse.

 

All that plus is not where the engine is at it's best so why do it....It makes no sense....

 

Thank you all... I am a new rider and these tips are so helpful

 

Along with the extreme loads put on all bearings, especially the connecting rods, it can cause detonation and wear on almost every other part.
Shifting at higher rpms has much less chance of causing issues, unless you miss a shift, overreving the engine.
I never shift to next higher gear below 3000rpm unless coasting with no load.
The newer bikes have much taller gearing, most recommend not using 6th gear until 65-70 mph. If your coasting, the rpm can drop much lower, but you should shift down to get to at least 2800 rpm before trying to accelerate.
For passing, I would automatically shift back to 5th, unless I was already going 80, big gobs of throttle at low revs put huge strain on the motor, 6th being the hardest on everything. jm2c fwiw Fastrider124

 

The answer to your question is that the engine will run at a uniform speed, when it is in its intended rev range. As engine speed drops, the crankshaft starts pulsing with each cylinder firing, so it is no longer running smoothly, but starts to jerk, or run erratically. That is when loads on bearings and other internal parts becomes excessive.

Be nice to your engine and change down if it starts doing that!

As for higher rpms, the engine has a rev limiter which prevents it over-revving, so no harm should be done by running it very fast. It will suddenly sound darned horrible and stop making power, but that is the protection system kicking in! Change up.....