08 S2 Low RPM concern

[chunkygoat]

If anybody can throw some input in - it'd be greatly appreciated.

Just for a little background on the bike:

I have a 2008 fz6 s2. It's been my every day commuter for almost 4 years now. It's got 25,000 miles on it, I've done 3 oil changes in its life - one at the beginning of each season. I've NEVER changed the air filter and know I need to - and its on my list. I've never dropped, tipped, or layed her down ever. The only mods I have are scorpion cans. Everything else is purely cosmetic (well frame sliders too). I've recently bought and installed a new chain and new rear tire. The clutch was tightened and a few things lubed by my mechanic less than 4 weeks ago.

Recently I've been experiencing a strange, hard to describe, feeling when I'm in the very low end of the RPM range (under 4k). I feel it mostly when I'm in slow moving traffic - with the clutch semi-depressed - working the friction zone, rear brake, and very low end of the RPM's to provide low speed stability (learned that at MSF).

The best I can describe it is that when I'm using the friction zone and the low end of the RPM range going 5mph, I can feel a sort of pulse. I can feel it in the somewhat in the clutch. I also notice this feeling when I'm in a high gear going slow (again using under 4k RPMS). It feels like something is moving, or maybe a slight "knocking". It's not loud and obvious, but only barely noticeable. If you weren't riding the bike, you wouldn't even notice. It almost feels like something is either loose, or maybe misaligned?

I'm not sure what would cause this as I am not too mechanically inclined. But at first it was slight, and over the period of a few weeks, has been getting more and more noticeable. I have a mounted cam on my bike and helmet - and was hoping to have some sort of video documentation to bring to help describe the issue - but the video doesn't display the problem in any sense.

So do any of you know what could cause a low RPM pulse feeling, as if something was loose, misaligned, or rattling. It is not noticeable at any RPM higher than 4 or 4.5k. Is it a possible sprocket issue? Should I look into getting new sprockets? Could it be transmission related? I doubt its related to the clutch because I feel it at times when the clutch is not in use.

Any input is greatly appreciated. If ya need any pictures or audio of up close, or any questions answered to describe it further - I'll do my best.

Thanks again.

-Matt

 

[FinalImpact]

So the bike and the Clutch lever have a pulse to them.
LEVER: like its moving a tiny bit
The BIKE: like its surging fore/aft with no rider induced changes to the controls?

First thing that comes to mind is warped rotors but that doesn't fit anything accpe the bike surge and would not be felt at the clutch lever.

I know you said allot; but throw out some more descriptions of what and when the Bike does this. Maybe even cold vs hot. but overall - I'm clueless. . .

 

[Nappa]

Looking at the things you've done to the bike, I don't see that you've changed the chain in all those miles. If it's getting worn / stretched, it can cause some vibrations. Just a thought.

 

[chunkygoat]

So the bike and the Clutch lever have a pulse to them.
LEVER: like its moving a tiny bit
The BIKE: like its surging fore/aft with no rider induced changes to the controls?

First thing that comes to mind is warped rotors but that doesn't fit anything accpe the bike surge and would not be felt at the clutch lever.

I know you said allot; but throw out some more descriptions of what and when the Bike does this. Maybe even cold vs hot. but overall - I'm clueless. . .

Alright it seems that whether the engine is warm or cool plays no role. It seems to happen cold just as often as warm. The lever doesn't necessarily pulse, I can feel it I would say in the throttle moreso. Its really noticable when I'm cruising at low RPM's or when I'm letting the clutch out from a stop sign and accelerating slowly. When I slip the clutch slowly, and begin to accelerate - I feel it.

What I envision is the the chain sliding on the sprocket horizontally. Or perhaps the sprocket is loose? It makes a small I want to say clicking/knocking noise, more felt than heard. There's no surge in acceleration, or sudden drop off.

If I kept the RPM's at a steady 3k, I would feel it consistently the entire time until I accelerate above 4k. I can almost imagine the sprocket being old and worn and the brand new chain is loose on it. Or the teeth of the sprocket are worn and the chain plays on it. The chain was just tightened and lubed so I don't think the chain is the issue. It almost feels like something is borderline going to slip or fall off. It's a slight knock or a rattle, not a grind.

Maybe I can poke around the block with my camera underneath and try to get it on film - maybe you can hear it.

Without letting a mechanic ride it thats my best description. Without any expert knowledge, I suspect it may be the sprockets but its really just a guess. What would the symptoms be of a pair of beat to hell sprockets with 25k miles on them? Bare in mind I have done the occasional wheelie but I really ride calm 92% of the time.

 

[Nappa]

Sorry I missed that part about the new chain.
It's usually a good idea to change both chain and sprockets.

 

[FinalImpact]

Off hand, I'd loosen the chain to limit and go for a run. If the wheel is aligned properly; back off the adjusters an equal amount (easy to do with feeler gauges), lock them down and then loosen the big nut and shove the wheel forward and tighten it. Feeler gauges are VERY HANDY for this.

Also check the run-out of the both the front and rear tires. Put a block under the headers and spin the wheel with something nearly touching the tire and make sure it turns true.

 

[ChevyFazer]

How many miles have you put on the bike since the new chain was installed? Also could you take a picture of your rear sprocket?

My bike has made a "knocking/clicking" noise a few times pretty much exactly the way you have described. I notice it way more right when I take off and up to about 15-20mph. In my bikes case it was caused by my chain being way too loose. So I tightened it up and went ahead and cleaned and lubed it while I was at it and the noise instantly disappeared.

I know you said that you don't think it's the chain because it is new and was just lubed and tightened, but if it's been on there for a while and the sprockets were pretty wore out since you didn't change them as well, the chain could be in a little worse shape then you think.

If you still have your center stand or a bike stand you could get the rear up and release the clutch in 1st with no throttle. This might let you see almost exactly what your chain is doing. Just keep in mind that since your weight won't be on the bike the chain will be a little looser then when your riding it. Not to mention doing this could be dangerous if your not careful.

 

[chunkygoat]

Thanks yall for the input. I think I've tracked down what's going on. Me and a few buddies sat around and I let them take it around the block to feel what I was talking about. Because I just replaced the chain, tightened it, and lubed it up - we determined it has to be the sprockets. This is my first bike and I'm not the most mechanically inclined person - so this is a learning process for me.

But apparently after some research - sprockets are supposed to be changed out any time you replace the chain. If not, you run the risk of wearing the chain out at an accelerated rate - which is news to me. I feel guilty for not researching this beforehand but you live you learn.

So what we came to conclude is that the sprockets - more particularly - the rear sprocket, is worn with rounded edges and not so much of a distinct point at the teeth. It's barely even visible the distinction between a good sprocket and a slightly worn sprocket - yet you can really feel the impact when riding. I also read if you over tightend the chain to compensate for what you would interpret as a slip - will only wear your chain and sprockets down even faster so I'm not too keen on tightening the chain again.

So the slightly rounded teeth are having trouble gripping the chain and its creating a low RPM chatter. It isn't bad enough to let the chain slip - but its borderline getting there. So I went ahead and bought sprockets online - OEM steel ones because they're supposed to last long unlike aluminum ones I've heard have a tendency to wear after 8 - 10k miles.

I'll try to post an update and let you know if it solves the chatter mystery - which I'm confident it will.

Thanks all for the input.

 

[TownsendsFJR1300]

Sorry I missed that part about the new chain.
It's usually a good idea to change both chain and sprockets.

+1 on the above.

My front sprocket was very worn at 12,000 miles (the original owner didn't lube it the first 4,500 miles).

If you pull off the ft sprocket cover, 3 bolts, look at the black plastic part of the sprocket.

It's likely the chain has worn thru the plastic part and WILL MAKE NOISE and you will feel it. The front sprocket gets more wear than the rear sprocket(tighter circumference) so I'd put my money the front is really bad...

You shouldn't be able to push the chain off the front sprocket with a screwdriver at all.. The chain will get tight spots over time (normal wear and tear) which again, you'll be able to feel, especially as slower speeds...

With 25,000 miles on the chain and sprockets, you got your moneys worth...

 

[fyrebug]

I'm having a similar issue with the bike surging in 1st gear and lurching. throttle control at a constant RPM also on an 08.

I'm going to check the chain and sprockets tonight, I'll be curious to see if you find that solves it.

 

[hk_fz6_05]

huh interesting....you almost to a word described a problem I've been experiencing recently. It started after a longish trip to Jutland (400km each way) and now I notice that felt and slightly heard rattling primarily in 1st at low rpms.

Only roughly say 25-30.000kms on the clock though. I don't have any seriously mechanically inclined friends around - would you guys say "take it to a mechanic"?

or is chain and sprocket changing a (reasonably) simple thing?

 

[TownsendsFJR1300]

huh interesting....you almost to a word described a problem I've been experiencing recently. It started after a longish trip to Jutland (400km each way) and now I notice that felt and slightly heard rattling primarily in 1st at low rpms.

Only roughly say 25-30.000kms on the clock though. I don't have any seriously mechanically inclined friends around - would you guys say "take it to a mechanic"?

or is chain and sprocket changing a (reasonably) simple thing?

If you have the proper sockets, are somewhat mechanically inclined and have a manual or checked for prior threads (I know there's many). its a very doable project.

The largest problem would be locating a chain riveting tool. They do make a regular, c-clip master link for the 530 chain however the rivet is genereally preferred (as its more secure).

Even if you had to buy the tools, it'd be cheaper than paying a mechainic and you now have some tools!

If you need a shop manual, PM me with the year bike and a full e-mail address, its a genuine Yamaha manual as a PDF file...

 

[hk_fz6_05]

thanks for that. might put that on my to-do list then. :BLAA: