Handlebar vibration big bore 2st

[sleepy]

Have you had the balance factor of the crank checked? It is quite possible to change the factor to a higher value which will move the vibration away from the RPM that is causing the problem.

[Gibbit]

The vertical component of the engine vibration is the one causing the problem  allowing the engine to pivot around the rear engine mount is how I have done it in the past. Harley handle bar mounts are a good source of isolation mounts (but for the imperial sizing)

Thanks. ill try and source some rubber washers or something.

Have you had the balance factor of the crank checked? It is quite possible to change the factor to a higher value which will move the vibration away from the RPM that is causing the problem.

No I haven't, but wish I did now while the crank was being rebuilt.

[sleepy]

You can't just chuck in some rubber washer and leave the rear loose as it will tear the mounts to pieces in a very short time. If you where to rubber mount the motor you would need to bore out all the mounting holes in the cases and fit proper rubber mounts with inner and outer steel sleeves, especially needed would be an inner sleeve so the bolt can be done up tight. Even if the rear mount is left tight it wouldn't take long before it worked loose and the swingarm would be loose as it is the rear mount.
Your only practical quick fix would be some sort of rubber mounts for the bars. Other thing to think of would be a radical gearing change to get the motor RPM below the vibration at the speed you want to go at.

[Gibbit]

You can't just chuck in some rubber washer and leave the rear loose as it will tear the mounts to pieces in a very short time. If you where to rubber mount the motor you would need to bore out all the mounting holes in the cases and fit proper rubber mounts with inner and outer steel sleeves, especially needed would be an inner sleeve so the bolt can be done up tight. Even if the rear mount is left tight it wouldn't take long before it worked loose and the swingarm would be loose as it is the rear mount.
Your only practical quick fix would be some sort of rubber mounts for the bars. Other thing to think of would be a radical gearing change to get the motor RPM below the vibration at the speed you want to go at.

Thanks for the info.  The rubber mounting idea sounds a bit too involved to do.  I have changed the gearing from(14/48) to (16/46) and I'll still fill the handlebars with silcone.

[80-85 husky]

there is a guy from qland on the café husky forum and he did some work to tone down his 400 husky vibes with good results. if you go on the forum, you may be able to search his thread.

[Gibbit]

Cheers Mate.

[Lozza]

Crank balance won't help much due to the vertical position of the cylinder (vibrations are why cylinders are angled) . If you have engine plates at the front new plates with rubber mounts are easy to fabricate as is welding new tabs on the frame. Toyota Camry engine mounts make ideal rubber mounts for the head stay.

[sleepy]

Have a read about engine balance, this article give quite a good explanation.

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

Let me give an example from a few years back. A 490 Maico crank turned up in my shop after being fitted with a Yamaha rod by a major engine shop in Brisbane, they had machined away a fair amount of the counter weights to fit the wider rod. The result was an engine that vibrated so badly at high RPM the owner couldn't hold the bars at all, making the bike almost unrideable. After new crank wheels were obtained and the rod fitted to maintain the original balance factor it returned to normal.

As for the front and top only rubber mounts, don't even think about it if you want the motor to stay in the frame for more than a few minutes not to mention the possibility of the frame breaking in half without the motor bolting securely to it acting as a brace. Think about the exhaust mounting as well with the front spigot having to deal with the motor moving up and down in the frame.

[djr]

Let me give an example from a few years back. A 490 Maico crank turned up in my shop after being fitted with a Yamaha rod by a major engine shop in Brisbane, they had machined away a fair amount of the counter weights to fit the wider rod. The result was an engine that vibrated so badly at high RPM the owner couldn't hold the bars at all, making the bike almost unrideable. After new crank wheels were obtained and the rod fitted to maintain the original balance factor it returned to normal.


just being curious here {I am not being critical or anything} ,
 why were new crank wheels  needed ?
had too much metal been removed, or too much needed too be removed to get it balanced ?
I only ask as I have heard of that Maico-Yamaha rod conversion before , but no mention of balance problems afterwords

[fred99999au]

major engine shop in Brisbane, they had machined away a fair amount of the counter weights to fit the wider rod.

[sleepy]

Let me give an example from a few years back. A 490 Maico crank turned up in my shop after being fitted with a Yamaha rod by a major engine shop in Brisbane, they had machined away a fair amount of the counter weights to fit the wider rod. The result was an engine that vibrated so badly at high RPM the owner couldn't hold the bars at all, making the bike almost unrideable. After new crank wheels were obtained and the rod fitted to maintain the original balance factor it returned to normal.


just being curious here {I am not being critical or anything} ,
 why were new crank wheels  needed ?
had too much metal been removed, or too much needed too be removed to get it balanced ?
I only ask as I have heard of that Maico-Yamaha rod conversion before , but no mention of balance problems afterwords

They had machined around 2mm of each inside face of the counter weight and if you've seen a 490 crank you would know that metal is all on the opposite side to the pin and it wasn't possible to remove enough weight from the pin side to get even close to the correct balance. It may have been possible to fill the crank with Mallory but the cost would have been greater than a used crank. Atleast the shop in question paid for the replacement wheels and vowed never to do do anymore jobs like it again.
Back when that conversion was done Maico rod were very hard to get and very expensive. The Yam rods could be obtained aftermarket then making them cheaper and if installed correctly would outlast the original by about 2 times due to the 3mm wider bigend. Only draw back was a heavier rod and .5mm extra length, I would bring the balance factor back to original and fit 1mm aluminium base gasket and they worked well.
A little side note for 465 & 490 Yamaha owners, the aftermarket rod being sold for them are actualy Maico 500 rods and are .5mm shorter than the original. 

[sleepy]

major engine shop in Brisbane, they had machined away a fair amount of the counter weights to fit the wider rod.

Not sure what it is you are trying to say? Is it a question to find out who did the work?

[mick25]

The way I see it , as sleepy has said fix the main problem balance the crank instead of trying ways around it , you may find a way to stop the vibration thorough the bars etc , but at the end of the day the engine is still down there vibrating it's head off not good .

[fred99999au]

no sleepy, poster below you was asking why it needed new crank wheels. I quoted your post of why it needed new crank wheels.

[sleepy]

no sleepy, poster below you was asking why it needed new crank wheels. I quoted your post of why it needed new crank wheels.

Ok, does make sense now you pointed it out.