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Flywheel Weight


b40rt
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  • 9 months later...

Just reading through this old post as we are about to embark on a little flywheel lightening on a red and white Guanaco. We have done the calc's and we are looking to shave 400grams.

We are baseing this on the burgat bible of many moons ago , but this would be for a later model. Has anybody done this on the earlier Gunaco and would 400 grams sound right. I am sure a little either way is not going to make a difference but are we in the right ball park.

Also another question for the SWM officinardos here, did the frames with the flat plate around the foot rest area ie. the first yellow ones, in fact surface pre 1980 as I have come across a very nice red and white gunaco with this, coupled to an first wave swinging arm. The owner tells me its a factory bike from the 1979, just before the start of the yellow phase. Any thoughts please.

Cheers

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  • 2 months later...
 
 

any updates on the flywheel front gentlemen?

There are two effects of lightening the flywheel, one is that the motor will pick up quicker due to less mass, the second is that it will stall easier at very low revs if it is too light.

The former is good if you ride sections that need immediate response to sharp throttle openings. The latter means that you will have to ride the bike constantly on the clutch at low revs to overcome the possibility it will stall. With the standard flywheel the SWM will drop to a virtual standstill without using the clutch, plonk very smoothly at this speed and will pick up smoothly with no snatch. With a flywheel that it too light the bike will not run as slowly without the clutch and will jerk and snatch, meaning you have to slip the clutch to overcome the snatch and stop it from stalling. If you're used to modern bikes and don't mind clutching everywhere then it's probably not going to be an issue.

In the end, it's all subjective and personal preference

First thing you have to ask is do you really need to do it as if you're not riding sections that need the engine to pick up revs very quickly there is no point. An SWM should pick up revs quick enough to cope with any classic trial and probably any easy route in a modern club trial.

Get a spare flywheel and take half a pound off it and try it. If you want more take another quarter off it until you get something you're happy with.

First thing I'd do is ride it as it is, as you might find it's fine...

As regards the lighter flywheel making it grip less in slippery conditions, it won't affect the bikes ability to grip, what it will do is make the bike spin up and break grip easier but it will still grip, just requires more input from the rider.

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There are two effects of lightening the flywheel, one is that the motor will pick up quicker due to less mass, the second is that it will stall easier at very low revs if it is too light.

The former is good if you ride sections that need immediate response to sharp throttle openings. The latter means that you will have to ride the bike constantly on the clutch at low revs to overcome the possibility it will stall. With the standard flywheel the SWM will drop to a virtual standstill without using the clutch, plonk very smoothly at this speed and will pick up smoothly with no snatch. With a flywheel that it too light the bike will not run as slowly without the clutch and will jerk and snatch, meaning you have to slip the clutch to overcome the snatch and stop it from stalling. If you're used to modern bikes and don't mind clutching everywhere then it's probably not going to be an issue.

In the end, it's all subjective and personal preference

First thing you have to ask is do you really need to do it as if you're not riding sections that need the engine to pick up revs very quickly there is no point. An SWM should pick up revs quick enough to cope with any classic trial and probably any easy route in a modern club trial.

Get a spare flywheel and take half a pound off it and try it. If you want more take another quarter off it until you get something you're happy with.

First thing I'd do is ride it as it is, as you might find it's fine...

As regards the lighter flywheel making it grip less in slippery conditions, it won't affect the bikes ability to grip, what it will do is make the bike spin up and break grip easier but it will still grip, just requires more input from the rider.

many thanks for the tips

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  • 6 months later...
 
  • 4 weeks later...
 
  • 11 months later...

Clutch side weight is 1.6kg so pick up is improved with it off. Still seems to grip ok and im still yet to stall it in the approx 6 weeks I have owned it and#33; Love it

 

 

Think 500g is nearer to the mark !

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  • 9 months later...
On 13/09/2010 at 11:42 PM, martinm said:

The very early red/white SWM used a smaller flywheel that the yellow models.....Sammy Miller used to list a bolt on flywheel weight in his catalogue many moons ago.

While in the flywheel area.......one of my talented SWM contacts has converted his bike to electronic ignition, with some very good results. It is utilising a kit thats already available on the market, and I have one winging its way to me shortly, to see if its as easy to install as he makes out..and whether the improvement is significant enough to warrant the money.

Will let you know the findings soon.

Martin

@martinm pretty exhaustive testing ..

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