"Odd" revving under hard acceleration

[Bram]

Hello,

While on a beautiful winterride in a cold (4°C) blue sky, I encountered a rather odd "problem" with my FZ6.

When I'm in first and second gear, and I accelerate hard, from 5K to 12K, I'm feeling and hearing something strange.
When approaching 8K, the rev's go up faster then normal, but i'm not feeling any harder acceleration. It's almost like the rear wheel is burning out a little bit when approaching the max BHP-area. The rev's dont go redline while it happens, but it jumps from 8K to 10K, and then back to 8-9K

I have had this a few times now, and it happens only while hard acceleration (about 90% throttle).

I first tought that my front sprocket was worn out, but it's not. The slack on the chain is also in spec.

The only thing that comes in my mind now it that the rear wheel really WAS burning out a little bit.
Is this possible? or is there something else in play?

The pressure in the rear wheel is 2,5bar, and i weigh about 58kg (inclusife gear)
Is it possible that the pressure is to high for my lightweight, so the contact area with the asphalt is to small so it loses traction under hard acceleration?

 

[92fz08]

What you described is what happens when your clutch is slipping, you can try adjusting the tension on it, sometimes that helps. basically the motors spins freely of the transmission or something like that. The Cold could have a factor in it to, its more likely to happen if your motor isnt warmed up.

 

[psnbye]

I kinda doubt its spinning the tire, but maybe, when the revs go up, is there a harsh vibration? Or is there a bad smell when you stop?

 

[Bram]

What you described is what happens when your clutch is slipping, you can try adjusting the tension on it, sometimes that helps. basically the motors spins freely of the transmission or something like that. The Cold could have a factor in it to, its more likely to happen if your motor isnt warmed up.

The engine was in operation temp while it happened. I never go hard in the first 15 minutes. don't want to hurt my baby
I'll check the tension of the clutch cable.

thanks for the quick post.

 

[Bram]

I kinda doubt its spinning the tire, but maybe, when the revs go up, is there a harsh vibration? Or is there a bad smell when you stop?

There are no odd vibrations. The revs going up quicker than normal, and back down al little bit are very strange and can be heard clearely. As if in accelleration, the clutch is pulled in just a little bit.
I didn't notice any bad smell though

 

[thieu]

Cold tires dont have much bite. And while your engine can be warmed up your tires can still be stone cold.

 

[dirtbiker1410]

Like mentioned above, it sounds like your clutch is slipping under hard acceleration. How many miles do you have on it? Might be a good idea to pull your clutch cover and check your friction plates out. Could also be from some nasty dirty oil in there too.

 

[thieu]

I might wish to add that if it was your clutch slipping you would be able to replicate the problem in ALL gears not just first and second. The clutch is between the engine and transmission an so the torque from the motor is the force trying the make it slip, and that torque does NOT change with the gear selected in the transmission.

And on a second note - old dirty oil will not cause the clutch to slip. The oil loses it's ability to lubricate as it gets used - not the other way around.

I am assuming the you are not using standard automotive oil that has anti friction modifiers in it. That will screw with your clutch - but again in all gears.

When this slip happens does or speedo rise as well?

 

[novaks47]

Maybe the chain is slipping, or rather jumping teeth. How are your sprockets doing? Chain tension?

EDIT : Actually read your post this time, looks like you've got that covered. LOL

Maybe it is just your tires. At those low temps, they may not be getting warmed up sufficiently.

 

[nextfriday]

Clutch is slipping. Adjust or replace.

 

[Bram]

Like mentioned above, it sounds like your clutch is slipping under hard acceleration. How many miles do you have on it? Might be a good idea to pull your clutch cover and check your friction plates out. Could also be from some nasty dirty oil in there too.

I don't know how many miles the clutch has. I bought the bike with 19.000km.
It has now 32.000km.
It needs a service in 800km. I will tell the mechanics to take a look at it.
(I go to a official yamaha dealership)

 

[Bram]

I might wish to add that if it was your clutch slipping you would be able to replicate the problem in ALL gears not just first and second. The clutch is between the engine and transmission an so the torque from the motor is the force trying the make it slip, and that torque does NOT change with the gear selected in the transmission.

And on a second note - old dirty oil will not cause the clutch to slip. The oil loses it's ability to lubricate as it gets used - not the other way around.

I am assuming the you are not using standard automotive oil that has anti friction modifiers in it. That will screw with your clutch - but again in all gears.

When this slip happens does or speedo rise as well?

Actually, I don't have the luxury to look at the speedo due to the warp-speed
It would be hard anyway, because the numbers are going upward anyhow, so a quicker increase of the numbers would be hard to spot as the refresh rate of the speedo is not realtime.

The oil being used, is the standard oil that yamaha dealers use to service the bike.

 

[flash]

What kind ouf oil are you using? Some synthetics are to slippery to use in bikes with a wet clutch. I sure does sound like clutch slippage though.

 

[Bram]

Most of you agree that it has something to do with the clutch. In my next service (in about 800km) I will ask the yammie-technicians to take a look at it.

Thanks to everyone here for the quick help. :thumbup:

 

[RJ2112]

Have you been learning to do wheelies, by chance?

If it only happens in 1st and second, is it possible that there is damage to the transmission? I think that very unlikely; but it's another potential answer. Very high torque in the shortest transmission ratios would be an area that a dog between gears may be damaged.

 

[Bram]

Have you been learning to do wheelies, by chance?

If it only happens in 1st and second, is it possible that there is damage to the transmission? I think that very unlikely; but it's another potential answer. Very high torque in the shortest transmission ratios would be an area that a dog between gears may be damaged.

I have tried to do a wheelie for about 5 times. but only power wheelies in 1th gear (roll off - roll on throttle). no clutch wheelies.
I don't know what the previous 2 owners did to the bike. Anything is possible

 

[Motogiro]

I agree, it sounds like the clutch. Make sure your cable is lubed and free moving. The clutch lever should have play in it. There is a thumb wheel adjustment right at the clutch lever. Make sure you have play in the lever. If the clutch lever is tight the clutch itself may not be fully engaged. The clutch on the FZ6 has a small friction zone. When the motor approaches 8k RPM is when it really starts to pull and deliver it's horse power. This may be when you're noticing it but if it's not adjusted correctly or the clutch is worn you will get slippage.

 

[Bram]

I agree, it sounds like the clutch. Make sure your cable is lubed and free moving. The clutch lever should have play in it. There is a thumb wheel adjustment right at the clutch lever. Make sure you have play in the lever. If the clutch lever is tight the clutch itself may not be fully engaged. The clutch on the FZ6 has a small friction zone. When the motor approaches 8k RPM is when it really starts to pull and deliver it's horse power. This may be when you're noticing it but if it's not adjusted correctly or the clutch is worn you will get slippage.

Thanks for the tips.
Who knew, I'm really learning stuff here

 

[greg]

if the tyres were slipping then i suspect you would notice it fishtailing a little bit

 

[thieu]

Have you been learning to do wheelies, by chance?

If it only happens in 1st and second, is it possible that there is damage to the transmission? I think that very unlikely; but it's another potential answer. Very high torque in the shortest transmission ratios would be an area that a dog between gears may be damaged.

If that scenario was true the slipping would be accompanied by a terrible noise!!