Upgrade silent blocks need to change frame cones?

[wrecklessrobbie]

Sorry I never meant to be snotty either.
It's hard at times to explain onesself at times in words. I'm not always the best.

I think the difference is that one has a slightly thinner part in the cone. In theory the bar will sit lower. Therefore giving a bit more room for bigger carbs and reedvalves. I think.
Apparently though they are either not needed or very difficult to fit.


Sorry I did not mean to confuse the thread.

Robbie

[Adam_Winstone]

As far as the 2 standard types go, the difference is that the ones with the chamfer on are taller (by the chamfer depth) than the corner cut ones... at least that should be the case with original factory ones. This extra depth/height protrudes slightly beyond the frame mount tube and sets the length by which the tube in the larger mounts can be pulled in by. If you fit the earlier shorter mounts then tightening the engine bolt pulls the mount's central tube in too far and stretches/stresses the rubber, which causes it to fail and break free from the rubber over time.

Adam

[sydduckett]

As an aside and I know it's not the topic... but you can drill the frame and use a grub screw to hold the offset cones in the correct positions. About the only way you can guarantee they won't move.

[wrecklessrobbie]

Why do we need frame cones?
What do they do?

[rosscla]

When you tighten the nuts on the stud they pull the cones into the taper on the frame and the gap closes gripping the stud.

Your engine doesn't rotate round the stud when your suspension goes up and down its the rubber in the mounting block that flexes.

[Monty]

Well I need to go and check all of mine coz I use the old cones

[Adam_Winstone]

^... That's the thing, they will work but not using the wrong ones does stress the rubber and lead to premature failure, which is why it is better to use the right cones for the right mounts.

[wrecklessrobbie]

So am I right in thinking then,
The engine bolt is held by cones. They stop the bar moving.
The silent block engine mounts are fixed solid in the engine.
The silent blocks once fitted into the engine are tightend up onto the engine bar with a wavy washer and locking nut.
How exactly does the engine move up and down?
If the rear shocker is removed the engine moves up and down. Is this just flexing of the rubber?

[Muppet]

rubber flexes

[rosscla]

Almost

So am I right in thinking then,
The engine bolt is held by cones. They stop the bar moving.
The outside shell of the silent block engine mounts are fixed solid in the engine.
The the inside tube of the silent blocks once fitted into the engine are tightend up onto the engine bar with a wavy washer and locking nut.
How exactly does the engine move up and down?
If the rear shocker is removed the engine moves up and down. Is this just flexing of the rubber?

The outer metal part rotates as much as the rubber allows, which is why the voided ones should be fitted a particular way.