Why is there a power loss when a motorcycle is climbing a mountainous road?

My motorcycle, Honda CG125 (single cylinder) is in perfect order… Runs fine on leveled road.

I have noticed that while climbing a mountainous road, initially it would run fine at lower gear and high rpm (7000+). But after some time, about 30 minutes, it would loose it power. Quite interestingly, I have noticed same behavior with other bikes.

I would like to have some technical reply i.e. How the power is lost at high RPM under load.

Shall appreciate, if links to some technical article and/or some animation is provided.

How to own a Honda CBR250RR back from the 90s in the USA?

I love this motorcycle so much, and this might sound crazy but I have a budget of 20K to get it over here. I would imagine that it would be as simple as flying over their and buying one then shipping it on a boat to a us port, fly back and wait for it to show up in the port. The problem is I don't know a single thing about shipping motorcycles across the pacific… I'm not even sure if theirs a company that does that. Would I have to Pirate it? But this is the price (real rough estimate)

round trip to Japan or Australia-$1,000-$2,000

buying the cbr250rr-$5,000

shipping it back-$?(this is the part I'm asking about)

Engine of my bike (Honda) produces cracking/knocking sound. What could be the possible cause?

I have checked the oil level using the dip stick, it is in good level.

There's no cracking/knocking sound when the engine is idle (onand running).

I have checked the chain, the tension is ok. Not too tight, not too loose.

Before I hear the cracking, a sound similar to rubbing rubber begins until I hear a "Tack" "Tack" "Tack" that seems like a metal rod is hitting the crank case. There's no constant interval with this sound. This usually happens when gaining and reducing speed. Between 2nd and 3rd gear.

When I started to switch on the engine in side stand position, continuous drops of oil is suspected coming from sprocket shaft.

What does oil in the radiator mean?

I just got a Honda cbr 600 f2 and it had a crack in the radiator cap so I look in it and it had oil in it. I just bought the bike and it runs and rides fine but It has oil in the radiator. I called the guy and asked him and he said he thought it was cracked but he said a mechanic told him it was a seal that was bad. I drove it home and the dude drove it to meet me which was about an hour drive for him. And it rode fine. I'm just trying to figure out what I need to do to fix it.

Motorcycles: What would be the better buy: 2006 Honda CBR600F4i or 2015 Honda CBR650F?

I have a 2007 Kawasaki 650R and have been thinking of trading because I've had the bike since 2007, which I bought new. I've been thinking of the Yamaha FZ-07,
but some have said it's too similar to bother changing for. I've always liked the yellow 2006 Honda CBR600F4i. I've never ridden an inline 4 before. Would it be a better move to buy a new 2015 CBR650R
over the used 2006 CBR600F4i even though the CBRD650F is underpowered? Thank you.

p.s. I'm also interested in the CBR600F4i because I've read they're very reliable and long lasting.

What is a good motorcycle stand for winter?

What is a good motorcycle stand for winter? - 1

Added (1). i got my first bike last spring now i need to winterize it but i can't seem to find a good stand to get the wheels off the ground. I have a 1100 honda shadow there's no center stand it just is lean. So i'm trying to find a stand to get the wheels off the ground but all i find are the large ones i just need one that isn't expensive. There are no shops near me. I was gonna order online. But all i can find are stand that get only one wheel off the ground at a time or are not ment for long term.

Motorcycle starts and revs but won't run?

I have a 2004 honda rebel 250, and it has a little trouble starting but i can get it started. When i rev the engine though, it starts to sound a little off and the whole bike vibrates like crazy. If i let off the clutch the bike pulls a bit, but it doesn't move if i give it throttle, like the clutch is burned out (but I think the clutch is fine).
Any suggestions as to what's wrong are highly appreciated.