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I ride a Honda Rebel 250 motorcycle and over the past few days I find that the bike is losing power when accelerating fast.

When I twist the throttle to accelerate quickly (in any gear) I hear the engine sound increasing in pitch by a lot more than I'm used to hearing, but the motorcycle doesn't seem to respond and performance is very poor. If I then twist it back to a position of slow acceleration, the engine noise returns to I'm used to hearing (still the accelerating noise but a lot lower pitch) and the performance also seems to be appropriate to that level of acceleration.

What could be wrong with the motorcycle?

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I am having the same issue, I have a 125cc ajs regal raptor, and if I am accelerating in well its mainly 4th gear and going up a slight incline it'll lose power and even if I knock it down into 3rd it'll struggle, but I think I may have a block in the air fliter or in the carbs, so it needs sorting, just something to think about next time you have a similer problem mate –  user3632 Sep 3 '13 at 20:25
    
@AdamRobinson the key here is that the RPMs increase without the motorcycle accelerating. This is the hallmark of a slipping clutch, and could not be explained by blocked air filter or carb issues. –  mac Sep 4 '13 at 15:49

2 Answers 2

up vote 11 down vote accepted

My knowledge of motorcycles is limited so I could be wrong, but it sounds like the clutch is slipping.

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I've had a mechanic look into it and yes, the problem was the clutch slipping. –  Paulo Pinto May 16 '11 at 21:17
    
Did he say why? Is it just worn out, or something to do with the oil? –  theUg May 25 '12 at 4:20
    
The clutch plates were worn out. –  Paulo Pinto Nov 15 '12 at 17:34
2  
Do you tend to ride with your hand on the clutch lever? if theres no play on the clutch lever you could accidentally be causing wear by keeping it slightly "on" –  Mauro Mar 8 '13 at 8:18

I realize this question has been answered, but keep in mind that any carbureted engine can bog down under throttle and cause a lack of acceleration.

If it can be backed off and regain acceleration, then I'd suggest carb tuning. If the engine revs, but no acceleration then it's a slipping clutch.

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