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Discussion Starter #1
Hi everyone,

Background:
I have a 2007 honda cbr 125.
It was stolen a few weeks ago, driven pretty wrecklessly, and now i got it back.

Problem 1:
Driving up hill, i get sort of hiccups on the motorcycle.
Like it slips out of gear for a second then reconnects.
When it slips, i lose thrus for a second, then like the gear reconnects and regains the thrust. It can happen every few seconds going up hill, and seems to get worse.
This can happen in first, second, third gear... probably even higher gears..
When i go on a flat road, not up hill, i dont get this issue.
If im driving someone, so the bike is heavier, this issue is more noticeable.

Problem 2:
Driving down hill, allowing the motorcycle to be slowed down by the current gear, i hear a grinding clunking sound. It sounds as if some clutch plate and the gears can't connect so they are just clunking at each other, if this makes sense?
I drive down hill, no need to use gas since im going fast enough, i let go and i hear these very scary metal clunking noises, even if i slow down with my brakes they are still hapening.
If i hold down my clutch the noises stop.
So now when i go down hill, i either accelerate with gas, or i have to slow down by holding the clutch and the break.
I can't let the motorcycle ride the gear down hill because of the metal hitting noises im hearing.

Both of these problems can happen on a straight road as well, if the forces are strong enough. Like if i drive fast and then switch the gears down i will get the clunking noises.
If im driving another person in the back i might have gear hiccups on almost straight roads, etc..

Any ideas? These problems seem to be getting worse.
Is it something i can fix by myself?
 

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Gone
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23,907 Posts
The first thing to check is the free play at the clutch lever.

If the free play adjustment is correct, I would suspect the clutch plates themselves may need replacement.

Make sure the chain is correctly adjusted according to the manual.
 

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Ace Tuner
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2,912 Posts
Sounds like the transmission is slipping in and out of gear. It could be a shift drum/shift fork problem because it does it in a few different gears.
Better news would be a shift mechanism problem. (Much easier to fix).

Having been stolen, they were probably rough on it. Makes me think shift drum and/or bent shift forks.
If it is slipping out of gear, be aware as you ride it more parts (mostly trans gears) are being damaged.
That means metal is getting in the motor oil and circulating thru the entire engine. Metal in the oil is never a good thing.
You could dump the motor oil and search for metal in it.

On the bright side, like Dodsfall said, if the drive chain is way,way too loose it could do what you describe. So check the chain for sure.
 

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I wouldn't rule out the clutch, but I agree with SemiFast with bent shift forks or shift drum. When you go uphill, if the clutch is slipping it will be worse in higher gears. For example, if 1st gear slips then 5th will slip much much worse.
 

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Discussion Starter #5
Hey, wanted to update for future generations.

The issue was chain slack.
I had about 6 cm chain slack, when the recommended is no more than 0.5.
After i tightened it, the problems went away.

I can understand why going up hill, the could possibly slip, and make it seem like the gear slipped or something.
What's weird is that when i went down hill, and relied on the gear to slow me down, it would make metal grinding noises. But when i held down the clutch, the noises would go away.
I though the chain kept rotating normally even if the clutch is pressed or not..

Anyways.. Thanks for the help.
Keep your chains tight! :)
 

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Retired twice: Navy and as a govt contractor
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14,301 Posts
PWN yes the chain keeps rotating but with the clutch in it is not under any pressure, just freewheeling.
 
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