Engine mount cones

[Storkfoot]

Plenty of grease to hold the cones in the desired position. You have to keep the bolt completely still whilst tightening the nuts , then the cones won't move from the position you've set them at , put one nut on the bolt with enough thread showing to get a pair of Mole grips on, thread the bolt through being careful not to move the cones and tighten from the other side whilst keeping the bolt stationary with the Moleys ! Visually check your wheel alignment from behind when done . Never had a problem with this method and had the engine in and out numerous times .

I did this, Mel. Still moved.

[coaster]

I'm thinking the key is that the cones need to be proud of the hole in the frame slightly prior to tightening and I'm not sure that is the case with the standard ones but as someone said earlier, we wouldn't know it the standard ones revolved or not.

[Digger]

I'm thinking the key is that the cones need to be proud of the hole in the frame slightly prior to tightening and I'm not sure that is the case with the standard ones but as someone said earlier, we wouldn't know it the standard ones revolved or not.

If they are proud of the hole that would imply that the tapers are not in full contact making it more likely that they would turn?

[HxPaul]

I suppose you could try threadlock on the outside of the cones and fit them,when they dry the threadlock may hold them in place until the engine bar is fitted and tightened.

[coaster]

If they are proud of the hole that would imply that the tapers are not in full contact making it more likely that they would turn?

I've just scribbled it out on a piece of paper and I think you are right, unless there is some sort of stop inside the engine pivot tube to prevent the cones moving in as far as they need to then provided the tapers match and everything is greased up then the cones ought to 'clamp' the bar tight.

Good call WT about fitting the shock before tightening it all up

[bike grim]

PS, I think the Atomic would clear the frame on a normally sized barrel, its just that the Avanti is a bit bigger.

I have an Atomic Reed valve ( not the mini version but don't know if it's described as "Ultimate", had it while) on my Rapido currently in series 1 and it doesn't clear the frame. I have had to take quite a bit off even with off set cones and a 300mm shock

[coaster]

PS, I think the Atomic would clear the frame on a normally sized barrel, its just that the Avanti is a bit bigger.

I have an Atomic Reed valve ( not the mini version but don't know if it's described as "Ultimate", had it while) on my Rapido currently in series 1 and it doesn't clear the frame. I have had to take quite a bit off even with off set cones and a 300mm shock

Combined with an Avanti, I don't think it would be possible to use a 300mm shock without a lot of re-modelling of the manifold with Devcon or similar.

[coaster]

Hmmh, maybe contact RM? Is it totally radical to thnk that maybe he designed it to be solely piston port?

I did chat to him about it a while back but it wasn't something he had considered at the time but then he did a limited run of crankcase induction reed valved Avanti's which I have heard are superb.

[rossclark]

I would have thought that a longer shock would move the the cylinder closer to the frame leading to less clearance on the manifold.

[coaster]

I would have thought that a longer shock would move the the cylinder closer to the frame leading to less clearance on the manifold.

It would Ross, I think I already have one of the shortest on there (R1 295mm)

[camel]

I use eccentric cones to clear the frame of my winter model with a mb shorty/muggello cylinder.
What i did was use silicone to bond the cones in the frame and allow to dry,silicone will allow some give for the cone too compress but keep them in the correct orientation.

[coaster]

I use eccentric cones to clear the frame of my winter model with a mb shorty/muggello cylinder.
What i did was use silicone to bond the cones in the frame and allow to dry,silicone will allow some give for the cone too compress but keep them in the correct orientation.

Now that sounds very plausible, if I go with the cones, I will try that

[Knowledge]

So if I have this right, the cones should tighten onto the bar so they effectively become one unit. Further tightening will lock the inner sleeves of the mounts to the bar/cone assembly and all suspension rotation is via the flex in the rubber in the mounts? If that's the case then if the cones rotate it must be due to possible wear in the frame or undersized cones?

Col,

This is my understanding. When you tighten the engine bolt, the inner "tubes" of the engine mount bush push the cones into the frame. The cone taper forces the cone to grip the engine bolt, and they all become one. The grease is only there to ease construction and prevent corrosion. Even is standard trim, the cones should not rotate.

Martin

[Storkfoot]

Are theory and practice the same though?

[coaster]

Are theory and practice the same though?

Martin is correct and I believe that it should all lock up solid but no doubt due to poor machining or wear there will be cases where this isn't achieved.

One thing bothering though, is it the same for the S1/S2 and early S3? Just thinking that there isn't much flex in the bush for suspension movement or doesn't it need much?

[cookieman66]

Hi im sure Dave Bristow on his old combo had off set cones drilled a hole for a grub screw to hold them in place more for when he had to remove the engine quick but could be done .Andy

[coaster]

Well , I dropped the engine, removed the manifold and applied a layer of JB weld to the inside and ground away some more of the top of the manifold. Decided to try it without the offset cones but is still fouled on the frame but took it for a decent run of 45 miles but the vibration I could feel indicated that it was definitely touching even with me sitting on it. So dropped the engine again and ground off some more with the dremel and also fitted the offset cones. Off for another spin and noted after a mile or so that the revs were hanging. Home again and dropped engine yet again, removed manifold and found I'd broken through the ally on the manifold during my last bit of fettling. More plastic metal and now running like a dream, vibration gone I checked in Sticky's spanners guide and there is no mention of how tight to do the silent block nuts up so I just did them as tight as I could using a socket and long handle.

Thanks for all your advice guys

[Warkton Tornado No.1]

I’ve followed this thread but refrained from comment.

I’m only saying something now as an attempt @ clarification.

Cones, whether offset or not, long or short type, do/should lock into the frame via the Silentblocs compressing them due to the internal tube component of them.

The Silentblocs are a stressed, moulded item that is designed to be further loaded via the rotation of the engine unit.

I am unaware of any official instruction of whether or not the M16 x 1.5 threaded bar should be tightened with the rear suspension in place, but it is the method I would advocate as most logical.

The torque loading of the fasteners should be based upon the grade of the fasteners; which may be probably 8.8 as a guesstimate. Be cautious if you don’t know the grade or heritage of the bar & nuts....However, as the thread is identical to the rear hub nut, you could do worse than use that value as a guide.

I only hope to have helped with this comment.