Single shock to Twin shock conversions

[Slakewell]

I'm unsure of these and how legal it all is. I have a 84 Rotax KTM 4 stroke which itself is a good pre 85 bike. I also have a twin shock 81 495 roller which with a little engineering could be use to convert the 4 stroke into a evo bike. Also given that the 84 comes standard with upsidedown forks whats the deal with rules that say no upsidedown forks in pre 85?

[firko]

I have an ominous feeling about this thread.

[JohnnyO]

Forget it..

[LWC82PE]

The forks are pre 85 legal if they are the originals with drum brake but they are not legal in Evo.Converting the 84 single shock to twinshock for evo should be illegal and in my opinion would destroy a rare and desirable bike. Rule of thumb if your converting anything from a newer model to use in an older class or to make it in theory eligible for a different class, than it is illegal. We dont want those dutch (or UK) style converted bikes here that represent nothing from the past! How ever if you have no intention to race vintage with it and only want to use it as a paddock bike around home or for trail  riding then by all means go ahead.

[Slakewell]

Hmm I think I have better idea ill leave the 84 standard, I do know were this spare KTM rotax motor and a very sad modified KTM rotax frame and build a twin shock evo bike from that as my next project using mostly the 81 495 roller.

[Husky500evo]

It should be Evo class legal to use the fourstroke Rotax motor in a twin shock frame , because the same motor came out in the twin shock '82 Can Am Sonic. But it would be a shame to see a twin shock KTM 495 roller modified for the purpose, because they are such a rare beast. 

[motomaniac]

Wheres the rule that says no upside down forks in pre 85?
Other than that read Johnny O's post.100 times!

[Slakewell]

It should be Evo class legal to use the fourstroke Rotax motor in a twin shock frame , because the same motor came out in the twin shock '82 Can Am Sonic. But it would be a shame to see a twin shock KTM 495 roller modified for the purpose, because they are such a rare beast. 

As much as I love the KTM 495 and I do have a long history with them the first one was never a great race bike a well done 390 will beat it to the flag every time with equal riders aboard. Ill fish about and maybe a 79 enduro frame could be better.

[LWC82PE]

Wheres the rule that says no upside down forks in pre 85?

There isnt one, they are allowed if they were availble then so that excludes 1985 onwards disc models. Like every part if it was available to purchase pre DEC 31st 1984 then you can use it. The 2 obvious ones are aftermarket Simons and OEM WP forks off the 1984 KTM's.

[Slakewell]

I rather have a set of well setup 43mm Yamaha forks any day of the week myself

[motomaniac]

Wheres the rule that says no upside down forks in pre 85?

There isnt one, they are allowed if they were availble then so that excludes 1985 onwards disc models. Like every part if it was available to purchase pre DEC 31st 1984 then you can use it. The 2 obvious ones are aftermarket Simons and OEM WP forks off the 1984 KTM's.

Yer Leith but CR's came with disc brakes in 84. I recently acquired a Simons manual that has part# etc form Simons forks for CR's including 84 models.:-)

[Evil Rudy]

twin shocks, tick
air cooled, tick
drum brakes, tick

looks like a duck... quacks like a duck

where's Nate?

[Maicojames]

If I had an 81 495 roller...I would put a 420cc KTM engine in it-like that power more than the 495. We are in about the same rules boat here in the US-for AHRMA at least. The 84 rotax was a great bike itself-IMO.
Where you could do a conversion here would be-for example an 82 495 engine in an 81 chassis is ok for GP( mostly 78-81 bikes class)-since it was really like design-same for a 82 490 Maico in an 81 chassis etc.

But, like has been said-build what you want and ride what you want. you may get hit by a bus next year-so enjoy your bikes first and foremost.

[Husky500evo]

     An '82 KTM 495 engine would technically not be Evo class legal in Australia, because it came out of a single shock bike and had a reed valve cylinder (where the '81 495 motor was piston port). You would probably only run into trouble with protests, if you finished with a top three placing at a title meeting.  The top three guys would probably end up in the same positions no matter what they were riding anyway. The '82 495 motor in the '81 KTM frame would make for an easier bike to ride though, as the '81 495 was an animal .
      Is it true, MaicoJames, that the AHRMA are introducing a 4 stroke class in GP or Ultima ?   

[bigk]

Hey Slake, I have a '79 250 enduro frame if you can use it.
Cheers,
K