Idle rev fluctuation

[Davew]

Just wondering what sort if fluctuation in revs I should be getting after balancing the carbs and setting the tps? Still getting unwanted vibes on my 2001 fzs600 and want to rule out any carb issues.

[Davew]

Meant to add, I've just fitted a new set of downpipes, should I redo my carb balancing as the old pipes had a few small holes.

[darrsi]

Wouldn't hurt to recheck the balance if you have the time to do so.


The needle should barely fluctuate at all really.


What air filter are you using, and is it very old, that could cause the needle to bounce about a bit if it was clogged up or if you're using a Hi-Flo one (they're crap).


Worth re-torquing the engine mount bolts, make sure they're tightened correctly and in good shape.


When you say unwanted vibes, where are you mainly feeling them, and is it at any particular revs or all the time?

[keratos]

Mine is a 2000. I have balanced with a Morgan carbtune and davida £180 dials. Mine fluctuates about 50 , at very most about 75, rpm. Advice  on this forum was along the lines of ...its never going to be still as age wears the carbs , deposits gunk jets , needles etc, minutest of air leaks through inlet rubbers, wear on engine valves and seals. But +/-50 doesn't seem to bad.

[Davew]

Just done the carb balance again and it was very slightly out.


reckon it fluctuates 100rpm max, so I think it's ok.


Just get vibes at various points on the rev range, mostly through the seat and tank.  Especially under hard acceleration/deceleration.


I get the usual slight vibes at 6k, but its the other ones that are a nuisance.  more of a resonance vibration/buzz.  I fitted new downpipes but that's not helped at all.


would a valve clearance possibly smooth it out?
 

[darrsi]

Are the new pipes touching anywhere where they shouldn't?


Are they torqued up correctly at the headers, i know when i took mine off a couple of years back they tended to slacken off a bit until they had bedded in properly, so i had to keep checking them for about 2 weeks.


Is the centre stand causing any vibration at all?


I know it can be bad for neighbours but if you keep the bike at high revs can you simulate the vibes when the bike is stationary?

[Davew]

will check centre stand.  everything else is torqued up as it should be.  The pipes fit well and don't touch anywhere.  No leaks either. 

[keratos]

In fact I'm guessing 50-100RPM as I dont have a tachometer and using the rev counter where the graduations between 1000 and 2000 are so large (500RPM) that small fluctuation of +/-50 to 100 should only just be perceivable so maybe I'm leaning toward more like +/- 100

[limax2]

Just get vibes at various points on the rev range, mostly through the seat and tank.  Especially under hard acceleration/deceleration.

Are the chain and sprockets in good order? When they are getting at the end of life you can get this effect. I'm not saying it is definitely that, but just something to take into account.

[Davew]

Just get vibes at various points on the rev range, mostly through the seat and tank.  Especially under hard acceleration/deceleration.

Are the chain and sprockets in good order? When they are getting at the end of life you can get this effect. I'm not saying it is definitely that, but just something to take into account.

yeah, they seem in good order with a fair bit of play left on the chain.  It's a resonant vibration from the engine which happens when it's in neutral too, so can't be related to the gears or the drive side of the bike.  I checked the front sprocket was tight too.

[darrsi]

Were the vibes there before you changed the exhaust system?

[Davew]

yeah, exactly the same.  I thought it was due to the knackered collector on the downpipes but sadly not.  Might go for a blast later and stop somewhere I can rev it a lot without annoying my neighbours to see if I can locate where it's coming from.

[His Dudeness]

100RPM difference isn't likely to cause a vibration imo. Sounds like you've got the carb balance pretty much spot on. Does the vibration come in at around 6000 RPM? Does it only happen when you're stopped or all the time?

[darrsi]

100RPM difference isn't likely to cause a vibration imo. Sounds like you've got the carb balance pretty much spot on. Does the vibration come in at around 6000 RPM? Does it only happen when you're stopped or all the time?

He said it happens at various points and in neutral too.


For it to do that it has to be metal on metal vibrating, and the only real things that would do that in my mind would be engine, tank or exhaust? (unless he has 'legs' like Oscar Pistorius)


I've had wing mirror glass, indicators and even headlight bulbs vibrate before but you wouldn't feel that through the seat or tank, they were just a bloody annoying noise.

[Davew]

100RPM difference isn't likely to cause a vibration imo. Sounds like you've got the carb balance pretty much spot on. Does the vibration come in at around 6000 RPM? Does it only happen when you're stopped or all the time?

He said it happens at various points and in neutral too.


For it to do that it has to be metal on metal vibrating, and the only real things that would do that in my mind would be engine, tank or exhaust? (unless he has 'legs' like Oscar Pistorius)


I've had wing mirror glass, indicators and even headlight bulbs vibrate before but you wouldn't feel that through the seat or tank, they were just a bloody annoying noise.

yeah its the engine I think, its a resonance vibration at specific engine revs whether riding or in neutral, not just the usual 6k.  gonna do a full filter change in case theres any air or fuel pressure issues.