Author Topic: USD forks and rear disc brake  (Read 505 times)

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Offline michael

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USD forks and rear disc brake
« on: December 27, 2017, 04:35:41 PM »
Hi all, just new here, but, how come usd forks and rear disc brake are a problem, I have a 83/84 KTM 504 and as far as I can see every production run from KTM brought a slightly different variant, I have seen another 504 with the same wp usd forks although the rear disc brake is of a ktm 500 84mod, anyway just wondering cheers michael
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Offline LWC82PE

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Re: USD forks and rear disc brake
« Reply #1 on: December 27, 2017, 05:28:03 PM »
Where is the problem?  84 model WP USD forks are legal for pre 85 VMX

https://forum.ozvmx.com/index.php?topic=41488.msg395415#msg395415

I dont know about rear disc but if the 84 model  KTM came factory fitted with rear disc then i would naturally think its legal in pre 85. Check MOMS to be sure.
« Last Edit: December 27, 2017, 05:31:00 PM by LWC82PE »
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Offline 80-85 husky

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Re: USD forks and rear disc brake
« Reply #2 on: December 27, 2017, 06:45:04 PM »
while the pre 88 cuttoff exists for VERI victorian vinduro, you will need to check on that eligibility on the VERI website. odd 504 appears but usually normal forks and disc front  drum rear

Offline roon

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Re: USD forks and rear disc brake
« Reply #3 on: December 31, 2017, 08:28:50 PM »
VTR states = no USD forks or rear discs (regardless of year)
I have a bike that qualifies in every way except for WP USD forks (production change mid year) and I want to ride it next year but that means I have to source a set of 50mm Showas, WPs or Marzocchis to slot into the triples or else swap complete front ends with another bike of the same manufacturer and vintage but with "standard forks"....
I can understand that non USD forks and rear drums can be a clear cut way to define "Vintage..."....its all about having fun and riding our old school bikes, some bikes might just need a bit of "backdating" to keep everyone happy....
Spending too much time online and not enough time riding: '73 CR250M, '76 XR75, '82 PE175Z, '85 IT490N, '76 Husky CC175, '76 Husky 360 Auto, '84 TE510, '01 VOR400, '04 VOR450, '00 VOR503, '75 CB400/4, '63 CB72, '81 Guzzi Le Mans II, '70 Guzzi Ambassador, '94 Guzzi NTX650, '15 BETA XTrainer

Offline gra1961

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Re: USD forks and rear disc brake
« Reply #4 on: January 01, 2018, 10:56:52 AM »
ktm 504's had disc front and conventional forks later 84 ktm 600 rotax had usd wp forks and  twin leader drum brakes front and rear

Offline michael

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Re: USD forks and rear disc brake
« Reply #5 on: January 01, 2018, 12:34:11 PM »
Do these items give you an unfair advantage or is it just looks, I was going to put a alloy swingarm  on the TT500 is that forbidden as well, first thing I noticed riding a Suzuki 500 2 stroke was a terrible lack of engine braking, very scary on the first corner cheers
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Offline 80-85 husky

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Re: USD forks and rear disc brake
« Reply #6 on: January 01, 2018, 01:29:15 PM »
as the late 70's and 80's were a time of significant advancement in muddaboiks design, the organisers work hard to give everyone a class to race in that has comparable bikes. in the 70's the elsinore revolutionised mx only to be shot down by the rm series in the late 70's early 80's. suspension went from 4" to 13" from 74 to 83 and powervalves, disc brakes and single shocks all appeared on various bikes. some and advantage and some advancements were two steps back.

foe vinduro's an  age cut off with technical no no's is a way of keeping fields relatively "relevant" to the period of the bikes and riders so although some bikes had tech details as rear discs and upside down forks etc, they are perceived to be the next generation of bikes and are as welcome as a fart in church. in 5 years or so, the age range will change and they will all be part of the next generation of blokes to be old and want their youth back...

i see you have got on a bike you have to ride.....there is a foot pedal and a front brake lever....these slow the bike down so you can go around a corner..if you are using the engine to slow you down....your not riding hard enough!! ;D accelerate to the corner then brake hard and then accelerate out...do not fluff around on a trailing throttle ::) everyone will pass you while you wait for the compression to slow you down.... ;D enjoy your riding 8)

Offline LWC82PE

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Re: USD forks and rear disc brake
« Reply #7 on: January 01, 2018, 02:42:58 PM »
Do these items give you an unfair advantage or is it just looks, I was going to put a alloy swingarm  on the TT500 is that forbidden as well, first thing I noticed riding a Suzuki 500 2 stroke was a terrible lack of engine braking, very scary on the first corner cheers

Depends what swingarm and what era

For example the Profab banana arms are not legal for pre 78 but the straight ones are. This is because the banana ones only came out during 1978.

And you would not be able to use an alloy suzuki swingarm or a later alloy TT arm in pre 78 either. No problems for EVO class though.
« Last Edit: January 01, 2018, 02:44:46 PM by LWC82PE »
Wanted - 1978 TS185 frame or frame&motor Frame # TS1852-24007  up to TS1852-39022 $$$ waiting

Offline KTM47

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Re: USD forks and rear disc brake
« Reply #8 on: January 02, 2018, 12:51:11 PM »
Where is the problem?  84 model WP USD forks are legal for pre 85 VMX

https://forum.ozvmx.com/index.php?topic=41488.msg395415#msg395415

I dont know about rear disc but if the 84 model  KTM came factory fitted with rear disc then i would naturally think its legal in pre 85. Check MOMS to be sure.

The 84 model KTMs had TLS drum brakes front and rear standard.  The funny thing is the 83 model had a front disc brake.  To my knowledge the first rear disc brake was the Kawasakis in 1986.
MAICOS RULE DESPITE THE FOOLS

1999 KTM 200, 1976/77 KTM 400,1981 Maico 490

Offline KTM47

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Re: USD forks and rear disc brake
« Reply #9 on: January 02, 2018, 12:55:09 PM »
Do these items give you an unfair advantage or is it just looks, I was going to put a alloy swingarm  on the TT500 is that forbidden as well, first thing I noticed riding a Suzuki 500 2 stroke was a terrible lack of engine braking, very scary on the first corner cheers

If you are using engine braking to slow you down you are risking head shake.  Big 2 strokes have got engine braking just not as much as a 4 stroke trail bike.  The modern 4 stroke MX bikes haven't got a lot of engine braking too.
MAICOS RULE DESPITE THE FOOLS

1999 KTM 200, 1976/77 KTM 400,1981 Maico 490