Dealing with vibes

[SHimmer45]

Just got my XL500 engined 250RS on the road and its rather vibey any one had experiencing bar end weights to tune out vibration?
or any suggestions or experience of other things like "bar snake"

[tevie54]

First thing to do is make sure your balance weights are timed correctly, then if you haven't already, fabricate a top engine mount, finally get some of those foam handlebar grips. The RS is a small framed bike and not designed for a thumping great 500 engine so it doesn't have the mass to absorb the sort of vibrations the 500 produces, oh a heavy duty chain helps and make sure your cush drive rubbers are in good condition as well.

[SHimmer45]

the engine has had the balance shaft removed, however it "only" produced a 20% balance apparently.
have fitted a 35/36 tooth sprocket to the rear which has sorted the cruising revs nicely.
fitted a couple of small bar ends but i think they need a little more mass.

i havent heard of people making a top mount for the engine.

its still early in its "development" but usable enough for me to trundle about on it.

taking inspiration from

[Smithy]

I'm in love! Aren't specials just fabulous, there's something about making a unique bike that really appeals to me. Well done and keep up the good work.

[tommy]

that's a really clean xl ,rs you have  shimmer45  grate job  if the bike is very vibey  it could be down to removing the balance shaft removed , tommy

[xbally]

Love it!Bet it wheelies like no tomorrow!Hope you can sort out the vibes.......

[guest564]

Removing the balance shaft will make it vibe, it may also cause the frame to crack. One of the selling features for the RS was that the balance shafts allowed them to use a lighter frame. You should fit a top mount.

[themoudie]

Aye shimmer,

Further encouragement to be had from this video, nice bike and smooth riding! 

XL500_quick!

My regards, Bill

[SHimmer45]

the posted bike isnt mine im afraid.
will be looking at a top mount over the winter then

[blew]

An xbr without the balancer? I'm glad I don't have any fillings to rattle loose.

[guest564]

An xbr without the balancer? I'm glad I don't have any fillings to rattle loose.

Its been done, on a race engine it can, apparently, give a 2bhp power increase but it wasn't something that I was inclined to try.

[Propellor]

If the balance shafts run at crank speed I wonder why the issue wasn't dealt with in the crank?

[guest564]

If the balance shafts run at crank speed I wonder why the issue wasn't dealt with in the crank?

There is only one balancer on the XBR engine so it works like a 180 degree parallel twin, the dual balancer shafts on the earlier models are supposed to be better, I forget why, something to do with harmonics.

[Propellor]

If the balance shafts run at crank speed I wonder why the issue wasn't dealt with in the crank?

There is only one balancer on the XBR engine so it works like a 90 degree V-twin, the dual balancer shafts on the earlier models are supposed to be better, I forget why, something to do with harmonics.

Thanks rhinoman.

I read all this stuff back in the seventies, but I'd forgotten it all!

Here's an easy to read little article I picked up on google.  It shows the basic principle involving the two balancer set up. I think secondary forces act at twice engine speed. Maybe this is the harmonic "thing" you were thinking of?

http://www.jampot.com/TechTips%5CGeneral/QuestionsBalance.pdf

Edit: this Looks better. Not read it as I'm off to work now. But the diagrams on page 10 pretty much explain the difference between the one and two balance shaft arrangement.

http://www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf

[guest564]

I just corrected that, I should have put 180-degree parallel twin, it was the Ducati Supermono that was balanced as a 90-degree V-twin. Twice engine speed is the second harmonic as described in the second article linked.