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[MartinB]

Anyone have idea ideas about this please? My bike seems to suffer from excessive vibration at the lower end of the rev range.
It seems to "thrum" through my helmet and earplugs but reduces the higher the revs. I've had several singles - 3 Enfields but never had this before. Mileage is under 3K but I don't know the history.

[stinkwheel]

One thing to try is loosening the engine mountings, giving the engine a kick a few times from different directions, then tightening them up again. Can alter the resonant frequency of the engine/frame unit.

You occasionally find a cracked or loose engine mount when you do this.

[MartinB]

Thank you.
I've seen this as a possible solution and will give it a try.
Looking at the mounts I'll need to do a fair bit of dismantling to access some of the nuts/bolts but it will be worth doing as it's driving me a bit frantic!
This is something I would normally do over the winter but I don't think I can wait that long as my senses won't stand it!

[stinkwheel]

There are also the carberry plates but I think that's curing a higher rev vibration.

https://accessories.hitchcocksmotorcycl ... case/38605

[MartinB]

Yes thanks seen them too-note our hosts do their own slant on the original. Going to look at the engine mountings first and take it from there. Got the next 5 days off so I'll have a play...........

[MartinB]

Right-I've managed to slacken all the engine mounting bolts off-next question-should I start the engine up before re-tightening them? Or should I just retighten? Is there any particular order they need to be re-tightened? Hopefully I can get the torque figures online.

[RoSy]

Have you also slackened the head steady? try and jack the engine up a few mil then, if 3mm drop it by 1.5 it doesn't have to be that precise, is what you are doing trying to stop the engine from sitting on the studs so there is a little free play around the studs, then pinch up all studs then tighten.. I did this to mine when I had it and it's almost vibration free, also double up on the head steady and really wang it up tight. But don't forget its a single not a multi!! it will vibrate.

[MartinB]

Thank you.
Yes I've loosened the head steady as well.
I thought about jacking up the engine so as you say I'll do that tomorrow and hopefully tighten the mounts in a different position leaving free play around the studs.
I appreciate a single will inherently vibrate-especially without a balancer.
I've also got a 1981 Honda CB250RS which is a bit snatchy in the transmission but little vibration due to the balancer and smaller volume.
My 2009 EFI IIRC wasn't this bad-can't believe an extra 35ccs makes much difference!
I've also owned several XBR 500's but again they have a balancer shaft which makes the engine quite smooth for a 500cc single.

[MartinB]

Well it's worked.....to my surprise.

As indicated above I jacked up the engine to see by how much it could be raised and then reduced the height by an estimate half.
I tightened the main engine mounting bolts first and was in the process of doing the others-leaving the head steady until last.
I had to do it outside as I don't have enough room easily to access both sides of the bike in my workshop.
It began to rain of course and then I managed to snap off one of the thinner bolts and I had to faff around opening up the garage to find a suitable replacement from my spares but I've finished it off this morning and just returned from a 10 mile shakedown run and it's most definitely much improved - thanks to all posters
Noting the Carberry plate and our host's version of it-has anyone tried one with much improvement? I can live with the residual vibes -it's a 535 single after all but my bike has a bar conversion and the mirrors do tend to NOT show much of any use in them at some speeds. They are the standard mirrors and no doubt there may be better alternatives .I don't like the bar end type as I only have limited room in and around my workshop and they make the bike too wide

[RoSy]

I've fitted an AVP to my C5 and I would say there is some improvement, I did notice the bars didn't shake so much at and just above tick over but I think it's more of a novelty that a fix.