Rear End Judder at Speed

[Guest]

Hi

Looking for some help please - I recently bought a '99 VFR800Fi (my first bike) and to be honest I think it's the muts nuts. Since collecting it 10 days 850 (s)miles ago it hasn't put a foot wrong buuuut ......

Riding it into work today I went to overtake (about 85-90) and there was very bad rear wheel judder. She was as smooth as anything up to that speed and I didn't try to push it past because the vibration was quite harsh - I may feel brave on the way back and see if it eases off past 90.

I went out with a group of mates on Tuesday night and caned her a bit and she was fine - I did feel some slight judder towards the end of the run but I put that down to the road surface which really wasn't good.

Today I was riding along a dual carriageway she was as smooth as you'd like all the way up to 80+ but when I went to overtake (so this happened under acceleration) the rear end started to judder very badly. It was quite harsh and seemed related to rear wheel speed so I don't think it's suspension realted - it almost felt as if the chain was riding the sprocket but there's no sign of that on the sprocket / chain.

I've visually checked the rear wheel and there's no dings / dents so I don't think the wheel is damaged and it spins fine in neutral on the centre stand so the rear brake seems ok. The wheel has obviously been balanced in the past but again there no sign that it's thrown a weight. The only thing I've noticed is that the chain does seem a little tight on the side stand (it was adjusted at the weekend) but on the centre stand it seems ok but then I don't understand how a tight chain could cause this. The Chain, Sprockets, Pads are all under 1000 miles old.

Any suggestions would be gratefully accepted.

Thanks All .... Kol

[Stu]

i would look at the chain tension first of all

get someone to help you

someone sat on the bike with weight on the seat so rear suspension is loaded and check the tension chains get tighter under tension

also check for any stiff links

also think about getting the rear wheel balanced again it could have thrown a weight or had a tyre fitted and not balanced and the old weights left on

check bearings too

ps pop in newbies and introduce yourself

Stu

[Guest]

Hi Stu

Thank you for your reply and advice - very much appreciated!

Spent my coffee break checking it through (can't adjust the chain tension as I'm still waiting for the correct tool being delivered) but I did find some tight spots on the chain so I've re-oiled the chain and freed the links - the tension seems better now and correct according to the manual so fingers crossed.

Will see if it's any better on the way home

Kol

[Stu]

the tight links wont help at all

infact i had a bike with a few tight links and it did vibrate more until i replaced the chain

Stu

[Guest]

My work on the chain has - if anything - made it worse (but I don't think it's related). Went for a long blip down the motorway to try try a few things to see if it was consistent but unfortunately not.

Before I went I checked the rear sprocket was lined up true which it was, rear wheel also seems aligned ok.

May have to change the title as - althougth it feels to me that it starts on the rear wheel it's the whole bike that shakes like i'm going over cobble stones at 50. So - updated symptoms:

1/ Doesn't seem to be speed related other than it seems to be over 60.

2/ Doesn't always happen - sometimes kicks in about 65 / other times took her up to eeeerm more than enough with no probs.

3/ Doesn't seem to be road surface related.

4/ Speed of acceleration doesn't seem to make a difference although if pushed I would say it's more frequent when accelerating in 5th / 6th (more torque used?).

5/ When it happens:

* gently easing off the throttle doesn't help -continues until below 50ish

* applying either brake gently doesn't help

* dipping the clutch makes no difference.

* trying to accelerate through it just makes it worse

If I had to try to reproduce it I would say it happens when accelerating in high gear and then backing off the throttle. This seems to start it oscillating and either acceleration or deceleration makes it worse. It really does feel "drive" related - almost feels like a loose back wheel but I feel no play in the wheel.

Suspension seems ok - only weird thing seems the chain and if I were to describe it I would say that instead of having a "tight" spot it seems to have a "loose" spot. I really am stumped - am thinking the drive sprocket may be loose but then why would it be intermittent?

All I can say is I am confused.com - think it may be a trip to a Honda Dealership and watching the £'s fly away

Still love the bike though -just gutted I can't figure this out and a sunny weekend is coming up! Any help will be gratefully received - aaargh

[Guest]

I would seriously reconsider the use of your bike in this state, if it is a bigger issue and causes a lock up, you could make the problem worse and be in a whole load of trouble

Could it be clutch related? you seem to have ruled everything else out..?

[rennie]

very difficult to diagnose this!

could be chain, could be either wheel balance, bad tyre, lots of other things.

if you have to ride it like it is take it steady!

hope you get it sorted quickly!

[Roadtorque]

looks like it will be trial & error sorting it out, OK if you've got time to spare,,

I think the dealer might be the quick fix & has probabley come across it before

[Guest]

Just wanted to say thanks to all for their advice - I bit the bullet today and left it at the workshop - think they're going to start it on Tuesday. They also didn't know but I've asked them to go over it with a fine tooth comb and check everything as well as fixing the problem - seemed the only sensible option.

So hopefully mid next week will be out on the road again.

Will be missing out on the bank holiday but I hope everyone on TMBF has a great time - I'll be there in spirit !!

[Guest]

Just wanted to post the solution - major issue was rear monoshock (watch out looks like the after market manufacturers are building to order now so long lead times) mixed with replacement headstock bearings. It would ride OK then (based on speed / road surface) would hit a resonant frequency and shake like riding over cobblestones.

All going good now - have had a few other issues but it's my own little moneypit now

[Pete]

Nice one kolw, glad you got it sorted in the end. Aren't bikes great for throwing money at?!

By the way, a good tip for when you post on speed related threads (if you care for my two penneth) - don't admit to breaking the speed limit!!!!! Naughty boy!

[Bill_on_a_bike]

Glad it's sorted mate, overtaking at 80 or 90 is exactly when you don't want these issues!.

Keep yourself shiney side up won't you

[Guest]

Did I say 80 or 90 - I must've meant 60 to 70 - oops

Your're right about the money - I'm thinking about getting my Honda her own bank account so I can set up a standing order

Thanks all

[Colin the Bear]

Your tech has probably checked but wheel bearings may have play/ be worn. Sounds like previous owner liked wheelies.