vibration at 4000 rpm

[rogz1a]

My Z1A has a vibration at 4000 rpm and above and I wondered if others on here have experienced this.
I rebuilt my motor (along with the rest of the bike) last year and this problem was there then and I have since stripped it down for other reasons (mainly a leaking valve guide between head and guide) and while apart I had the crank stripped and balanced by S.E.P kegworth, new pistons and rebore, and some cylinder head work. Also had the clutch springs replaced. I have checked all bearings and for anything obviously damaged/worn (gears, bearings, alternator rotor etc. etc and I really couldn't find a thing wrong) S.E.P also said that all crank bearings were perfect.
This vibration starts at about 4200rpm in any gear and increases as the revs climb and about 5000 it levels off. It happens in any gear and I have noticed it if I rev it at idle. There is no abnormal noises with this except a lovely howl from the exhaust
I have now finished the first stage of running in at no more than 4000 rpm and have now discovered this problem. I mainly feel it through the footpegs and also the seat but not through the tank or handlebars. The bike is standard except for a Marvin 4 into 1 exhaust( I have wondered if this exhaust is the problem).I am also running it with the old points ignition as well.
There is no power loss and the bike pulls through all gears really well. I now need to recheck the shims and carbs after the run in period but I don't think this would be the cause ( it is a bit lumpy on tickover and I can hear a slight rattle from one of the shims at tickover)
As the motor runs so well I don't think its a serious problem but at 60mph and above it just becomes a bit uncomfortable. If this is how Z's are then please tell me. It's been 20 years since I last rode it and I can't remember it like this.
Please help with any suggestions as it is just spoiling what is a fantastic bike . Thanks, Rog

[hillbilly]

have you had the tyres balanced. my gsx750f does that,at 115mph and at 30mph.

[tlc]

My thousand does it near 5,000 rpm.

I don`t notice it too much but my pillion does. Since this equates to 75 mph plus I just ride slower.

[PAULJAC47]

If you pull the clutch in when the vibration starts is it still evident?
I think you need to see if this is drivetrain or engine side...In answer to your question if all Zeds do this? the answer is no!
Would check as Brent says wheel balance,engine mounts,chain and sprockets lining up,wheel and sprocket bearings,may be worth checking cush drive as well,chain not kinked worn,hooked sprocket teeth?
Cheers Paul J

[Pigford]

Check engine mounting bolts are tight

[Al]

The 'J' used to do it and it drove me mad.
The PO simply changed the final drive sprocket so that it didnt co-respond with motorway speed.

Replaced chain, sprockets,, wheel bearings, swing arm bearings, another chain, beefed up the cush drive, so on and so on. Stripped the engine and sent the crank to SEP for them to measure, strip, clean, assemble, true and weld but not balance.

Changed the bearing behind the final drive sprocket and the expensive one behind the clutch.

It stopped doing it but only found two things.
The final drive bearing was very bad when i got it out to see in clear daylight and the 'capped' needle roller bearing on the LHS of the input shaft was moving sideways in the crankcases. Reason for the latter was the amount of gasket sealer i used when putting the engine together last time and the low torque value of the very long 6mm bolts at that location. ie. they couldnt close the crank cases together there properly, allowing lateral movement in the needle roller bearing against its' 'knock pin'. So the; input shaft / gears / clutch pack was 'floating'.


AL

[z1bman]

could be the output shaft bearing as these were a common problem. also has the exhaust been fitted without the rubber mountings in the frame ?

[rogz1a]

Thanks for all the replys. This could be a long process of elimination.
The tyres are new bridgestone BT45 and balanced.
I have checked all bearings in the gearbox and all were smooth and have been around engine bolts as well as all other bolts I can get to and all tight. The rear exhaust mountings are the proper kawa mounts and are new
Now to the chain and sprocket. It is an old Regina 630 o ring chain but I did fit new sprockets. The new front sprocket did have a small offset but I didn't have the spacer to go behind the rear sprocket and I noticed that the chain was slighty over to one side. I have now fitted the original front sprocket with no improvement I know the chain and sprocket should be replaced as a set ( no bollockings please) but money was getting a bit tight and perhaps I was a bit too keen to get it back on the road
One thing I have noticed is that I have to adjust the chain alot so I have wondered if 20 years in storage hasn't done it any favours. The cush drive also has a bit of play in it. Yes all good points to look at and I am thinking that I should have replace the chain and may be the cush drive (':oops:') . What size chain do you use now that chain technology has moved on and which is the best brand. I will try and pull the clutch in and see if it disappears next time I'm out on it
One thing I hope is that it doesn't turn out to be the gearbox bearings in the end. I don't want to strip this motor again
One thought I had is if I fit smaller Z900 sprockets to bring the revs down would this effect the performance too much? ( this, I suppose, is also just hiding the problem and I would prefer to get it right). Also where can I get the thin rear sprocket spacer from. Z power don't do them.
Cheers once again, Rog

[Pigford]

Try Talon (Yeovil) for the sprockets & spacers, etc.

[PAULJAC47]

Rog, B4 you start shelling out,see if you can pull the chain away from the rear sprocket at all,Look at the rear sprocket is it clean on one side and greasy on the other if it is you have a mis alignment prob,how are you adjusting chain? to eliminate cush drive without shelling £70 for a new one get hold of old pushbike inner tube cut sections with scissors like big rubber bands and stretch them over cush drive blocks this will take up slack and point out if this is the prob or contributing to it...Good luck Paul J

[jimmock]

RogZ1A, GORGEOUS looking Z1A.

I like the pipe.

When, where did you buy that and how much??

The paintwork looks stunning. Where, when etc etc etc.


Jimmock.

[rogz1a]

Never heard of Talon but found the website. They don't list Z1A on the dropdown menu but I'm guessing they can get them in (or make them) Are they expensive. They look expensive(':shock:')

Paul, I can't pull the chain away from the rear sprocket and I didn't notice any wear marks on the back of it but when I viewed the chain from behind I could see it was over towards the outside of the bike ( hope that make sense).
My original non offset sprocket did have wear marks on the back and the chain had worn the inner casing slightly (which is why the offset sprocket was fitted)
I will try to pack out the cush drive, Cheers for that. I am using the marks on the swinging arm to adjust the chain and there seems to be plenty of adjustment left but as I've said I seem to have to adjust the chain much too often ( keep getting the clunk when changing gear) This could also be down to the cush drive. Umm think we may be getting somewhere on this.
Plenty to do in the next few days, Cheers

[rogz1a]

Cheer Jimmock. Got the pipe from exactrep and Hutch did the paint

[chrisNI]

If you rev it past four in neutral does it blip cleanly or shake?

[rogz1a]

Update.

Chris, I have just warmed the bike up and it does vibrate at 4000 plus on tickover. This eliminates the drivechain I also pulled the clutch in and had no change. Then I touched various engine casings to see if there was a particular area but there wasn't any significant vibration from any of them. But when I grabbed hold of the exhaust around the collector box with a thick rag I could feel a vibration.
So this seems to be the area to look at. I've got to take it back off within the next week to do an oil change. I'm going to look at the rear mount as Z1bman has suggested as this is very close where the vibration is worse.
Once again thanks for all the suggestion and if anyone out there has a Marvin exhaust with a similar fault please get in touch.
One other thing is that on the rear mount I made my own bracket to hold down the center stand as I didn't like the one supplied with the Marvin. It is also supposed to fit on the other side. I wonder if this is the cause as it's on the same bolt as the exhaust mount.
I will keep you posted when I have exhausted all posibilities