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Plunger Frames For Trials?


51mon
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Hi,

 

I'm really keen on getting a Rigid (I like a challenge!) and while top choice would be something like a nice big Matchless, funds just aren't going to stretch that far at the moment.  I've been looking at little Bantam's and the most available option at the right price is by far a plunger framed version.

 

Are plunger frames going to be any use or will I be fighting a losing battle?  I will be buying it as a bit of a project but will be trying to keep it reasonably standard so would rather not start replacing the rear loops to get rid of the plungers.

 

Any opinions would be appreciated!

 

Thanks!

 

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take a loooong good hard luck at evevery pre 65 clip on you tube check out the members and their bikes on the yorks classic website subscribe to the excellent emag on these pages read every copy of off road review and add up the number of plunger framed bikes.. take a hint..

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Hi Guy's.

 

Hi Simon.

 

Look my first trials bike I built was a James  with Plunger suspension?? Why ? well I found the bike for £5.00 for sale on the side of the road at the edge of the village I lived in, and I only had five pounds saved up from my pocket money in my jam jar.

It was a good decision !! because that got me into the trials riding game. I had to fit a 350 x18 rear tyre (Tire) . there was not enough clearance for a  full 400.

But this little bike started me off with a life time of building trials bikes the way I wanted them, and there is nothing wrong with that.

A BSA Bantam plunger frame is an easy convert to a Ridged Competition D1 Bantam, You just need to remove the plunger castings and replace them with two laser cut plates welded in to the right position to hold the rear wheel. Job done.

Forks are another thing you can have fun with to keep them period.

 

Good luck with the project.

 

Regards Charlie.

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Thanks for your thoughts chaps!

I see what you mean about the lack of plunger frames being used and there's obviously a reason? That said, like Charlie says, as a first time proper project bike the bantam might be a good idea after all, as a cheap option? Instead of cutting and welding maybe the plunger units could be locked out somehow? I'll keep looking either way, don't think the idea of a rigid is going to go away!

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If you fancy a challenge and a (relatively) cheap route into the sport without being too bothered about your score, then a lightweight plunger would do it for you. Remember, a decent rider on a poor bike can still put up a reasonable performance - it just needs riding.

I'd be wary of altering a standard bike's suspension to ride in a different class though, that sort of thing is known to raise eyebrows, if not hackles, which is all rather unpleasant.

Edited by cleanorbust
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If you fancy a challenge and a (relatively) cheap route into the sport without being too bothered about your score, then a lightweight plunger would do it for you. Remember, a decent rider on a poor bike can still put up a reasonable performance - it just needs riding.

I'd be wary of altering a standard bike's suspension to ride in a different class though, that sort of thing is known to raise eyebrows, if not hackles, which is all rather unpleasant.

So you are saying a plunger is a twinshock then ?  :popcorn:

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I feel like I've opened a new can of worms!

On a serious note though (not that it matters either way to a future purchase), I'd always assumed that plungers were classed in with rigids? Is that the case? The more you actually think about it the more they are Twinshocks?!

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Hi Guy's.

 

Well I probably won  one of the first awards riding a plunger framed James then, it was the best newcomer award for a novice riding the Banbury NOBAC trials in 1961-2.

 

This club went on to support me for most of my trials riding over the years, it is just a pity that it had to fold when the old membership could not find younger guys to take on there mantle.

 

Regards Charlie.

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Hi All,

 

Sorry to be boring but anyone who feels that a plunger-'sprung' bike should be classed as a twinshock just hasn't ridden enough of the old plunger models to understand the problem............

 

The worst element was the width of tyre that could be fitted - 'cos there was definitely more 'give' in the sidewalls of a 4.00 x 19 (yes, originally we were all on 19 inch rears way back) than there ever was in the sidewall of a 3.50 x 19 ( especially 'cos 3.50 Trials Universals were few and far between so most people used a 'Grasshopper' cover - which was basically a road tyre.)

 

Then there was the weight - even manufacturers like AJS/Matchless held off putting suspension on their trials models because their designers were sure the added weight of the limited travel and poorly damped original suspension units far outweighed any advantage over the much lighter rigid back ends.  The decision point came when Bob Manns unofficially fitted rear suspension on his works AMC bike and beat all comers in the 1954 West of England national trial - overnight the other manufacturers raced to get sprung models available - Johnny Draper told me the BSA works riders were told to fit their trials motors into their scrambles frames for a couple of weeks.............. 

 

I have ridden - years ago - all sorts of plunger models and they varied from feeling just 'soggy' at the back to a close relative of a pogo stick - they were inevitably fitted with the smaller Villiers motors in those days and that was essentially a far more significant problem to solve than worrying about the complications of springing.  

 

Then add the next difference between then and now - when we had finished riding in the trial, we had to ride the bike home and then, on Monday morning, early, back on the same bike and off to work...........and that kept the scope of any competition plans carefully limited.  (that, by the way, was not simply 'cos we didn't have works support - get together with Gordon Jackson and Johnny Giles and get them to tell you about riding a works AJS and a works Triumph together from their homes in Kent, through London in the early hours, then away on the Great West Road to compete in trials in the west country.................'twas a different world.)

 

Enjoy - but remember that riding the old bikes today you are only recreating a very small part of nostalgia.

 

Cheers

Deryk

Edited by laird387
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Hi Guy's

Deryk.

You are so true about the Monday morning thing.

 

On the James I described above, I would bolt back onto the bars the little spotlight that I used to be able to get back home after work on the bike, in the dark nights of winter.

This and the tiny rear light that never seemed to work? well it kept blowing the bulb? the lights were connected up to the direct lighting connection on the magneto, and this somehow sapped the power for the spark, so when the lights were plugged in,no switch just a push in connector the revs had to be kept well up, or the motor would die.

So the route home was interesting to say the least, there was no shutting off or the lights would dim and the engine cut out.

This gave me the bad  habit of taking the John Cooper racing position , around bends. well there is no way you could lean the bike in, it had to be kept upright.

I seemed to end up pushing the bike in the dark more than riding it home,and my dinner was almost always warming in the oven when i eventually got home.

Happy Days.

 

Regards Charlie.

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