Twinshock Rules?

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zulujack
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Twinshock Rules?

Postby zulujack » Fri Mar 29, 2019 12:37 pm

Hi All

Toying with the idea of building a twinshock, but not sure where to find information about the different categories and what sort of mods are allowed for each..

Any links to rules, etc... I could check out?

JC



David Lahey
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Re: Twinshock Rules?

Postby David Lahey » Fri Mar 29, 2019 7:09 pm

Here are the rules that apply if you want to compete in MA events. Look at page 249.

http://www.ma.org.au/licences-rules/rul ... ion-rules/

There are only two popular classes of competition for twinshock-type bikes nowadays. One for pre-65 and one for pre-87 twinshocks.
There are major parts that have to be of the period or look the same as those made in the period so for example if you are going to make a frame, it has to look the same as a particular frame from the era. This avoids people turning up with modern designs that have been converted to using twin rear shocks, or custom-made designs that have more modern levels of mass centralisation. There are a few monoshock bikes made pre-86 but they are not eligible either. The front end and motor needs to be from the right era too. You can use any drum brakes from the era you are going to ride in, so if you wanted, you could fit an early 1980s YZ twin leading shoe front brake on a pre-87 bike.

People commonly make minor chassis mods like footpeg location and shockie mount locations. It's not like in vintage motocross where you are limited to a certain amount of suspension travel. Aftermarket and home-made swingarms and triple clamps are fairly common in pre-87 twinshock trials.

I'm assuming you are Aussie. The eligibility rules are different in other parts of the world.


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zulujack
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Re: Twinshock Rules?

Postby zulujack » Fri Mar 29, 2019 8:35 pm

Thanks for that. I'm assuming the engine and chassis have to match also, or can you use a different engine from the same manufacturer as an example?



David Lahey
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Re: Twinshock Rules?

Postby David Lahey » Fri Mar 29, 2019 10:44 pm

zulujack wrote:Thanks for that. I'm assuming the engine and chassis have to match also, or can you use a different engine from the same manufacturer as an example?

No they don't have to match numbers or even brands. You can put a Suzuki engine in a Bultaco for example. The important thing is that the motor comes from a twinshock bike from before 1987 so you can't put a Yamaha mono engine in a twinshock frame


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David Lahey
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Re: Twinshock Rules?

Postby David Lahey » Fri Mar 29, 2019 10:50 pm

One thing I've always wondered is would a motor from a 1980 DT175 (non-linkage monoshock trailbike) be eligible to use in a TY175 frame for twinshock pre-87. They are functionally extremely close to a TY175 motor and much more plentiful so if the DT175 motor was allowed then there might be more TY175s in use


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Re: Twinshock Rules?

Postby Jon V8 » Sat Apr 13, 2019 5:32 am

They were used in limited numbers back in the day.Are any of these in Australia ? A mate here owns frame number 007.
Attachments
Chapman BSA.jpg
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Twinshock200
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Re: Twinshock Rules?

Postby Twinshock200 » Sat Apr 13, 2019 8:42 am

Is that a bike from Mike Chapman, Stratford on Avon MCC John ??


Where have all the Pre 65 Classic bikes gone ?

David Lahey
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Re: Twinshock Rules?

Postby David Lahey » Sat Apr 13, 2019 9:15 am

Jon V8 wrote:They were used in limited numbers back in the day.Are any of these in Australia ? A mate here owns frame number 007.

I've never seen one over here. Have you ridden your mates 007? (cool number). I'd love an informed opinion of what they are like to ride.
Some off-road events over here you have to put a big ID sticker on your bike and I was stoked at one such event to have been given 007 as my number. At the same event the Landowner was a young hippy woman who enthusiastically took photos of her infant son perched on my TY250A because it looked so "retro". I remember saying "it's not retro, it really is old"


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Re: Twinshock Rules?

Postby Jon V8 » Tue Apr 16, 2019 4:25 pm

Hi Roger, yes the Chapman is the bike Mike Chapman was responsible for. Apparently the first ever production monoshock trials bike. I'd forgotten we had discussed them over on Trials Central;
https://www.trialscentral.com/forums/to ... ent-287740
David, I've not ridden 007, its tucked away in a mates garage,all safe hidden behind a BSA Gold Star and an HT5 Ariel if I remember rightly.I'll have a word, see if I can "borrow" it ! I agree,being a Bond fan,its a cool frame number to have.Might take a while as all of our focus is currently on WW2 army bikes this year as we are off to Normandy for the 75th D-Day anniversary.



David Lahey
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Re: Twinshock Rules?

Postby David Lahey » Tue Apr 16, 2019 7:09 pm

Jon V8 wrote:Might take a while as all of our focus is currently on WW2 army bikes this year as we are off to Normandy for the 75th D-Day anniversary.

WOW!!!!!! excellent 8) that sounds like great fun


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