Diagnosing a lumpy ride?

[upshift]

Over the past few months, my bike has developed a rather lumpy (for lack of better description) ride, which I would describe as an annoying front-to-back motion. I don't believe it's the same surging issue that some folks have reported, where the engine hunts for correct RPM, due to the closed/open loop thing - more of a sense that power is not consistently being delivered to the wheel. It's particularly noticeable when cruising (less so under hard acceleration or deceleration), in lower gears (when increased momentum isn't helping smooth things out), and at lower RPMs (although it happens at higher ones, too). The bike has 41,000km and is otherwise in good shape.
 
Over the past two month, I've done the following to try to solve the problem:
[ul type=disc][*]Drained fuel tank and replaced with fresh gas[*]Changed spark plugs[*]Replaced chain and sprockets[*]Done throttle body synch[*]Done 42K valve check and adjustment[/ul]
Originally, I thought it might have been an engine issue but now I'm starting to think it's a drivetrain issue, as the engine sounds pretty smooth and the back-and-forth motion seems to disappear when the clutch is pulled in. 
 
Any thoughts on what to target next?

[betoney]

Correct chain slack? dont go by what the manual recommends, set it at 1" - 1.25" of slack.

[upshift]

Have slack in the clutch cable? Standard type of oil in the engine? Brakes not dragging? Just eliciting more data. Welcome back btw.

Thanks for the speedy replies, @piotrek and @betoney. 
Standard synthetic oil in the engine (Motul synthetic 10W40).
Brakes don't seem to drag (both wheels spin pretty freely by hand).
Chain slack currently set at 28mm.
 
Clutch cable has a reasonable amount of slack, I think (about a 2 credit card gap at the hinge, as recommended by

). The clutch engages really early and really fast, though (ie. as soon as I start letting it out, requiring very little lever movement), which makes me wonder whether it's fully disengaging when fully out. Not sure how I'd check that.
 
Thanks for the welcome back - full trip report to follow...

[nhchris]

 
 
Fuel filter clean?  Gas tank venting properly to avoid partial vacuum?
 
Could a cylinder be occasionally dropping out due to a leaky coil, intermittent ground, etc.?
 
But you did not mention throwing any error codes, so...
 
How about your tires?  Weird rubber can manifest itself in strange ways. Inflation pressure OK? No flat spots? Cupping on the front?  Are they both perfectly round?  Shifted belts?
 
Yada yada Yada...  and good luck!
 
cb

[1moreroad]

Is it rocking on the suspension? Any leaks at the shock or forks? Any changes to your weight or what you carry? Any new additions affecting aerodynamics (windscreen, luggage, etc.)? Is preload set up for you?

[skipperT]

Sounds to me like you’ve got a tight spot in your drivechain, esp if you’re at 41k km on the original chain. And yes, I did see the above reply that your slack is in spec, but here’s what you need to do:
 
Put the bike on the center stand and slowly rotate the rear wheel, and check the chain tension at many different places in the chain. Rotate, check tension, move the wheel, check it again, etc and repeat this until you’ve checked the entire chain (mark a link if you need to).
 
If you still think the tension is even all the way around (and it’s still around 1-1.5” slack), the next step is to purposely tighten the chain beyond what you normally run it. Wind the adjusters in 3 to 6 “flats” (or 1/2 to 1 full turn), re torque the axle nut and repeat the tests. Now is there a tight spot that’s apparent? If the tension in the chain isn’t around 20-30mm slack then you need to tighten the adjusters some more and repeat the tests.
 
A tight spot in the chain shows up this way by moving very little in one spot when pressed toward the swingarm and moving a lot in another spot. Basically, the freeplay isn’t consistent throughout the length of the chain. This is where the “roughness” or lack of smoothness in the driveline comes from.
 
Last inspection is to visually inspect the sprocket teeth and look for wear.
 
What I’ve detailed is a thorough drivetrain inspection. Let us know if that turns anything up.
 
-Skip

[upshift]

Thanks much for the input, @piotrek , @nhchris , @1moreroad , and @skippert .
 
To answer your queries/suggestions:
 
1. Yes, I can move the clutch lever back and forth a few degrees before it feels like is starts to activate the clutch. I have shorty levers on so there's not too much free play but there's definitely some. I loosened it off as much as I could at the handlebar adjustment screw.
 
2. I can't say for certain about fuel filter, venting, or cylinder dropping but it hasn't thrown any codes so I was assuming these were fine. The tires are relatively new Pilot Road 5s with good tread and good inflation and no obvious flat spots or cupping (ie. when I pull in the clutch and let the bike roll, it doesn't replicate the lumpy motion).
 
3. I had the suspension done last year (Ohlins shock, GP piston kit) and they replaced the fork seals, polished the tubes, and set it up for my weight. Haven't added any new farkles, such as windscreen or baggage recently, either.
 
4. The chain and sprockets are basically new (less than 1000km on both). Just for fun, I checked for tight spots, as you'd suggested, and found none. Chain slack is a very consistent 28mm all around.
 
Had it out for a boot today and the lumpiness is still there, and man is it annoying! (even making me wonder whether I need to start looking for a new bike!)
Gonna try to take it in to a shop this week and see if they have better luck finding the problem. Will keep you posted.
 
Thanks again to everyone who rang in with ideas - this forum is an awesome resource!

[norcal616]

Is this noticeable in 6th gear doing 25mph for example? or is it noticeable in a certain throttle position in any gear??? or have you done the APS adjustment mod in the past??

[upshift]

Is this noticeable in 6th gear doing 25mph for example? or is it noticeable in a certain throttle position in any gear??? or have you done the APS adjustment mod in the past??

Thanks, @norcal616. 
I don't think I've ever done 25 mph in 6th gear but it's definitely more noticeable at slower speeds in any gear and with the throttle at lower openings. I'm assuming that's because the lack of forward momentum allows whatever's causing the stumble to assert itself more noticeably. At higher speeds (in any gear), it becomes less noticeable. The effect is worst in 1st gear (which is also typically when I'm going slowest), where it's become truly painful to ride, due to the intrusion of the front and back motion.
 
I've never done the APS adjustment mod. My understanding is that, because it's a Canadian bike, I don't have access to the APS diagnostic menu (I tried accessing it a while back, following the detailed steps provided on this forum, but it doesn't show up on my settings menu like it does for US bikes). Rumour was that a dealership could access it, though, but the bike had been running fine so I didn't explore that route.

[skipperT]

Ok sounds like you ruled the chain and sprockets out. The only other thing I can think of in that area is wheel bearings or that the rear sprocket isn’t seated in the wheel hub evenly, but that would have turned up in your inspection of the chain if you sighted down along the chain.
 
I’m assuming the front sprocket nut is still tight and that you staked it back down?
 
You also stated that it goes away when you pull in the clutch lever and coast the bike.
 
So I think you might be back to some sort of running characteristic, provided everything prior checks out and is torqued still. The valves were checked and adjusted how many miles ago? Did it run better at that point or did you notice it was worse shortly after that visit?
 
Other items that might cause this are poor fueling in part throttle positions, which is what the APS adjustment does - makes the YCC-T system not as sensitive. Is the ecm flashed? PC-V installed? What about one of those devices that fools the FI system into running in open loop? (Can’t remember what they are called, PCommander calls it an O2 optimizer).
 
A bad or “lazy” o2 sensor could cause this as well and not throw any codes. You would probably see a drop in fuel mileage as well.
 
Any other mods done to the bike?
 
Checked for DTC’s? Your bike being a 15-16 (even though it’s a Canadian model) you should be able to access DIAG mode and check for codes.
 
Does it still accelerate smoothly with no hesitation or stumbling at WOT or under hard acceleration?
 
-Skip

[superfist]

I'll add one more thing to check. You mentioned newish tires. Has it started sometime not long after replacing the rear tire?
 
At that mileage you could also check the rear wheel drive damper. It's just rubber blocks inside the rear wheel assembly to soften drive-line lash, but if it's dried out, improperly installed, cracked or otherwise damaged it could give an inconsistent drive line feel like you're describing.
 
Edit: 41km = approximately a little over 25k miles. Valves checked and adjusted with the last service?
 

[jo1000]

This seems like a tough one. First thought was chain and sprockets , but you changed those. Have you looked at the air cleaner or have the dealer plugged in to the ECU ?

[upshift]

Thanks for your input, @piotrek , @skippert , and @superfist .
 
1. Pio, thanks for the corrections - in retrospect, I believe I was thinking of the TPS menu adjustment, which I thought was not adjustable on Canadian models (but now you've got me questioning that, too). Will check the clutch actuator arm for slack, as well.
 
2. Skip/Super, my valves were just adjusted (I've put about 300km on the bike since). It feels like the power is back to where it used to be but the rough ride hasn't abated. It goes pretty good under WOT and has thrown no engine codes, which I take to mean that the engine is generally in good form and that the problem is more likely drivetrain-related. Fuel mileage has been remarkably consistent through my time with the bike (5L/100km). The ECU was apparently flashed by 2wheeldynoworks before I bought the bike and it has no Power Commander, O2 mod, or other performance-related mods, as far as I know.
 
3. Supe, in retrospect, my tires aren't that new (I put new rubber on in May) and I didn't noticed the lumpiness until early July so suspect they aren't the cause. The bike also still seems to roll reasonably smoothly with the clutch pulled in, which makes me guess that the tires are fine.
 
My current thinking is that the following should be my next areas of exploration:
1. Wheel bearings and real wheel drive damper (thanks for that, Super - had no idea that this even existed)
2. Clutch
3. APS
 
I don't have the space, tools, or know-how to tackle all of these, myself, so will be getting some outside help - I'll keep you posted on progress.
 
Thanks again for the ongoing support.

[upshift]

This seems like a tough one. First thought was chain and sprockets , but you changed those. Have you looked at the air cleaner or have the dealer plugged in to the ECU ?

I cleaned the air cleaner when I replaced the spark plugs in July, but that didn't seem to fix the problem. 
Haven't had the dealer plug it in, yet - I've been resisting this, as I don't currently have a dealer nearby that I trust.
Might have to bite the bullet and go this route, if I can't get it sorted, myself.
 
Thanks for your thoughts.

[leonardlloyd]

He reports that he has replaced chain, indicating that it is new. Fast/early engaging clutch suggests that it may not disengage fully, making for issues in shifting or locating neutral, rather than the symptoms he experiences. Fuel filter or air supply to fuel tank seem more likely than other possibilities listed, given all that has been addressed.