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Why are bike engines solid mounted
sonic - 23/9/20 at 08:04 PM

a theoretical question

why carn't bike engines in a kit car have rubber engine mounts to take some of the vibration away ?

Edwardo - 23/9/20 at 08:14 PM

Good question - and one I've been pondering too recently!

Mr Whippy - 23/9/20 at 08:16 PM

Probably no good reason at all. Although I have never owned a BEC I did once solid mount a Pinto in my Falcon and my god it was horrific. Could you not simply use rubber bushes on the engine cradle?

watsonpj - 23/9/20 at 08:43 PM

Mines on metallastic bushes is not relly solid mount but the rubber is pretty thin walled. I can't see any real reason you could have a more flexible mount to isolate more.

paulf - 23/9/20 at 09:30 PM

They are solid mounted in the bike as they form part of the structure, as does the engine gearbox combo in many race cars but not really a need to in a road car.

adithorp - 23/9/20 at 09:53 PM

quote:
Originally posted by watsonpj
Mines on metallastic bushes...


Mine is too. No reason it should be solid mounted. Having driven cars where they are solid mounted, I can say that even though the bushes are thin walled as watsonpj says, they reduce vibration significantly.

40inches - 23/9/20 at 09:55 PM

I rubber mounted my ZX9R, it made a difference, not a lot but enough to make it worthwhile
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SPYDER - 24/9/20 at 12:07 AM

We incorporated Metalastik bushes into our engine cradle too. It still feels quite solid but they are hopefully just compliant enough to take the edge off of the shock loads and to tame vibrations a bit.


nick205 - 24/9/20 at 08:34 AM

quote:
Originally posted by paulf
They are solid mounted in the bike as they form part of the structure, as does the engine gearbox combo in many race cars but not really a need to in a road car.


I'm not a motorcyclist and haven't had a BEC, but this was my thinking. I once drove a tin top with a solid mounted car engine and the noise and vibration was horrendous. Short journey bearable, longer journey (20+ miles) no thanks!

watsonpj - 24/9/20 at 02:35 PM

Just like driving a BEC anyway :-) , you don't notice the engine vibration due to the +6k (at 70mph) and the noise from the exhaust and (rattle) from the quaife reverse box when running at the constant speeds. I still love it but there are times when i kind of think that I should swap back to a car engine (must be getting old).

steve m - 24/9/20 at 03:55 PM

Ive had many Motorbikes, and another reason i feel that engines are hard mounted, is that they are smaller capacity rev a lot higher, and will be balanced to a higher standard than most normal car engines, hence no requirment to rubber mount them

Except for my Old Norton 850 commando, with its weird mountings front and back, that were to aid in the engine not ripping the lugs off the frame !!!

steve

trikerneil - 26/9/20 at 10:03 PM

'79 - '81 Yamaha XS1100 had a rubber mounted engine to reduce vibration.
First mod is to fit solid mounts to stiffen the frame so it will go round corners better.

coyoteboy - 27/9/20 at 10:33 AM

Two obvious reasons are 1) it's a stressed member, you reduce the weight of the bike if you can use the engine as part of the chassis and 2) you really don't want a chain drive having alignment changes under high loads - extra wear, potential for misalignment of the rotational axes.

sonic - 27/9/20 at 07:27 PM

in a car application the above would not matter as running a propshaft, take the point ab out the quaife reversing box mine sounds awfull and was thinking of taking in out and doing away with reverse.