Engine vibrations

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#1 Post by **mangocrazy** » Mon Jun 29, 2015 11:55 am

I'm currently in the South of France with a couple of mates (it's a dirty job, but someone has to do it) and I rode the blue Falco down to start its tour of duty down here, allowing the red Falco to come back to Blighty. It's really instructive to ride two bikes that are supposedly the same back to back, as all sort of little differences (and some large ones) emerge.

On the way down I became more and more aware of vibrations at higher revs (above about 6000 rpm) on the blue bike, to the point that my hands were tingling when I got off the bike. The vibes also snapped my home made aluminium bracket for the hydraulic preload adjuster (or at least I'm assuming that's what did it). At lower revs it wasn't too intrusive, but once we started getting a move on (and we were doing plenty of that) then the vibes really started to make themselves an annoyance.

Jumping on to the red bike once we got to the gaff proved the point. On the red bike you can feel the engine, but it's not intrusive and the (minor) level of vibrations is consistent throughout the rev range, not getting worse as the revs increase.

So - what do you reckon is causing it? I did the valve clearances the winter before last and had to bugger about with the balance shaft in the head. Is it possible to get the balance shaft out by a tooth (or two)? Or is it something else? I'd heard the clutch bearings can go on these motors at around 30k, and mine's done 32k.

Any suggestions welcomed...

D-Rider · #2 Post by **D-Rider** » Mon Jun 29, 2015 1:10 pm

Well there are a number of possibilities - the balance shaft was one that came to my mind before I read that far - but like you, I don't know whether that's possible.

Did Aprilia do a limited-edition Anne Summers special? I'm sure Pete would know.

HisNibbs · #3 Post by **HisNibbs** » Mon Jun 29, 2015 1:42 pm

TBs, trim pots and chain adjustment/condition come to mind. However if it is possible to fit the balance shaft out of place then that might do it but I'd think it would need to be more than 5 degrees or so out of phase for you to feel it.

Firestarter · #4 Post by **Firestarter** » Mon Jun 29, 2015 2:10 pm

Does it stop when you pull the clutch in, i.e. engine dependent rather than speed dependent? Could rule out chain if so. Chain would be more lumpy than vibey I would think (I've had an overly-tight tight spot, and it felt like a misfire)

#5 Post by **mangocrazy** » Mon Jun 29, 2015 2:39 pm

It is engine rpm-dependent. It only gets intrusive above about 5-6k rpm. Don't think that fits with trim pots or chain. It's fuelling really well and the chain is new-ish, properly adjusted and Scottoiled.

Not sure about the balance shaft. It's very possible to mis-fit the cam chain, but not sure about the balance shaft. I think an FB post on AP is in the offing.

Aladinsaneuk · #6 Post by **Aladinsaneuk** » Mon Jun 29, 2015 4:29 pm

Check and adjust the bar end weights - they can be fitted loose if that makes sense

And not certain about the ann summers edition - who is brave enough to ask Miss Isle of Wight TT?

fatboy · #7 Post by **fatboy** » Mon Jun 29, 2015 5:54 pm

Surely if the balance shaft was the issue then the vibes would have been awful from the onset ?

#8 Post by **mangocrazy** » Mon Jun 29, 2015 9:20 pm

fatboy wrote:Surely if the balance shaft was the issue then the vibes would have been awful from the onset ?

Good point , well made... But I didn't use it much last year, apart from an RS rideout or two, and I think I forgot about it over the winter. This year's RS Trentside rideout got me thinking, and Sheffield to the South of France at high speed reinforced the view that the vibes were just too much.

The red Falco was waiting for me in the S of F, and the difference was really marked. It's much smoother and seems to spin up noticeably quicker (but that may be the Forza Aprilia chip designed for my 2 into 2 exhaust).

fatboy · #9 Post by **fatboy** » Tue Jun 30, 2015 7:01 pm

Well,here's hoping that it's something just worked loose.
My last ' it feels so rough its gonna blow up' was rear sprocket nuts ( despite the use of loctite )
Fingers crossed.

#10 Post by **mangocrazy** » Fri Jul 03, 2015 4:11 pm

Cheers FB. I didn't really have time to do any in depth investigations, and the bike has been left in the S of F ready for when we go down again. I'll definitely check the rear sprocket nuts next time.

Got a reply from Griff, and he says the balance weights can be reassembled a tooth or two out, so if I can't find any other culprit, that will get done this coming winter.

flatlander · #11 Post by **flatlander** » Fri Jul 03, 2015 11:13 pm

I didn't read it all but from what I could gather you're not getting good vibrations ?

#12 Post by **mangocrazy** » Sat Jul 04, 2015 11:09 am

Sorry Geoff, couldn't find any pictures to put in for you...

Aladinsaneuk · #13 Post by **Aladinsaneuk** » Sat Jul 04, 2015 5:54 pm

So put the crayons away Geoff....

goonerfromlag · #14 Post by **goonerfromlag** » Thu Oct 01, 2015 3:17 pm

Hello, noob falco owner here, did you get any further with this @mangocrazy? I'm getting the exact same symptoms as you: intrusive vibes from 5K revs, none at all below that.

#15 Post by **mangocrazy** » Thu Oct 01, 2015 5:43 pm

The bike is still in France (and so am I), but it will be heading back to Blighty with me next weekend (in the van). When I get back (and deal with all the cr@p that will undoubtedly be waiting for me) I'll take it down to Griff's for the great man to check out. But I doubt that will be much before mid-November at the earliest, sorry...