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Discussion Starter #1
Hi guys, I am currently having some problems with my CBR500R. The bike is a 2013 model and has 40k kms on it. About 2 months ago I started noticing loss of acceleration which worsened over time. The loss of acceleration would be minimal at the start of a ride, but would progressively get worse as the bike heats up. No indications of overheating or anything would come up. I initially thought it was the spark plugs or intake/exhaust valves but the problem persisted after servicing them. The only issue I found was an increase in 2 exhaust valve clearances but swapped the shims and now they're within spec. I don't know where to go from here so any help would be appreciated.

Cheers, Alex
 

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It does sound like th clutch is slipping. It could do this and still have proper freeplay at the lever if the plates are worn. Pretty low mileage for that to happen, but I guess it depends on how its been ridden.
 

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So engine still smooth no missfires, no work carried out on the bike in conjunction with the start of the problem.
 

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Give you've addressed the valve clearances, and spark plugs, I'd look at the air/fuel system. Silly to ask, but has the air filter been removed and inspected? It wouldn't be the first time if a mouse decided to stuff the air box with nesting material. I'm just thinking out loud here, but this problem almost sounds like the electric fuel pump is starting to fail and not pumping enough fuel as it gets warmer after being engaged for a while.
 

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If for the same road speed, the engine speed is now different, as the poster indicates, it can't be fuel or spark, it has to be mechanical, something in the transmission system (between the crankshaft and rear wheel) is slipping!! The only real culprit can be the clutch or the final chain slipping on the sprockets (but I think you would hear and feel that), the gears in the gearbox cannot change (unless teeth come off and you will know that very quickly!), if the clutch plates are worn or warped then the clutch can slip. Anything else slipping other than the clutch would make some terrible noises and fail quite quickly, you need to take the right engine casing off and inspect your clutch, measure the thickness of the plain and fiber plates and make sure all the plain plates are flat (I am sure the honda maintenance/service manual describes how to do this). I would also check the front and rear sprockets just to make sure the teeth are all present!!

Gary
 

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Discussion Starter #9
Cheers for the ideas guys, I am going to check the clutch first to see if it is slipping then I'll come back on here for other ideas if the problem still persists. Appreciate all the help (y)
 

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Did you change the oil before noticing the problem? If so, what kind of oil did you use?

I ask because motorcycle wet clutches are not compatible with most automotive oils; a 5W30 or 10W40 motorcycle oil is not the same as a generic 5W30 or 10W40 car engine oil. Friction modifiers used in car oils will cause motorcycle wet clutches to slip.
 

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Discussion Starter #11
That's a good point mate, I did change the oil a few months before noticing the problem but I used the genuine honda oil which is a 10W30. I've used this oil on my bike for years and never had this problem with it.
 
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