OzVMX Forum
Clubroom => Tech Talk => Topic started by: Slakewell on February 15, 2011, 04:39:15 pm
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Im converting (almost completely remaking ) a 80's swingarm to fit my 77 KTM whilst I'm sure it will do nothing to make the bike handle better this bike is being built as a hot rod. I still would like to ride this bike at the nats thou so I'm unsure how anal people get about this?
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I doubt you'll be allowed to ride it in pre '78, although it wouldn't bother me.
Cheers,
K
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It depends on whether it's an alloy arm you're fitting to it and if they were available for KTM's in '77.
They probably were available but does it look period correct? Could be a can of worms...
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Yes it alloy and it doesn't really look like swing arms you could buy back in the day. It dose look like allot of stuff I have seen on other bikes thou. Not that it makes it right.
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Why dont you get a DG arm off a Suzuki or something period and modify that.....theres a guy up here making them to suit RMA's and B's.....awesome replica...food for thought.
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Why dont you get a DG arm off a Suzuki or something period and modify that.....theres a guy up here making them to suit RMA's and B's.....awesome replica...food for thought.
That's the go Mr Crochet ;)
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Slackwell, If you happen to find yourself near the pointy end at the titles or win by the proverbial mile even though the bike looks the goods and has no real advantage, you will be protested I can almost guarantee that ::) ;)
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I would hunt around for a nice PDI cantilever arm, that way you will go much faster plus be pre 78 legal .... hell PDI arm is almost cheating ;)
(http://i245.photobucket.com/albums/gg71/marcFX_photo/Marcsnewtoy005.jpg)
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Hmm that would be almost a bolt on , I'm want a different look thou
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How does one of those things make you "go much faster"?
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I saw a Cr250M with billet tripples but what got my confused was the DG square box arm ? it was gold like the late model DG head on it, but i kinda think that would be out of period ? is a DG square arm on a CR PRe75 ok or out ????
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It would/Should not be allowed unless the 80's swing arm is identical (same part number) to the one your replacing which obviously it isn't. Sorry but i would be disapointed if it was allowed especially in pre 78. You might be able to twist the rules to sneak it into evo though.
The other option is to build your own or get GMC to do one. That way you can almost built it how ever you like but just make sure it looks fairly period and similar to what aftermarket swingarms were around then.
You need to ask your self, were people racing in 77/78 with a swing arm off a 1980's model? No they were not. Thats an easy way to work out if a part is legal.
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Dont want to Highjack the post but ,what about a Thor alloy arm on a 77 Husky? I dont think thay were available then, but I love to be proved wrong ;)
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Dont want to Highjack the post but ,what about a Thor alloy arm on a 77 Husky? I dont think thay were available then, but I love to be proved wrong ;)
I mean there are few alloy arms out there that are 78 or even pre 74 legal like ole Firko's Boyd and Starlings or PDI;D
(http://i245.photobucket.com/albums/gg71/marcFX_photo/IMG_3308.jpg)
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SO are DG squre arms not pre 75 legal then ?
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I have a copy of the '1974 Dirt Bike Buyer's Guide' in front of me, which covers all the bikes and aftermarket goodies available in 1974. In the 'Frames & Swingarms' section, there aren't any DG products in that listing. However, you could buy a square or rectangular section swingarm, in 1974, from Red Line, Cycle Products West, Alex Steel Products and Ocelot. Those four manufacturers all display square and rectangular swingarms, both stock length and extended, for Honda, Yamaha, Kawasaki, Suzuki, Bultaco, Jawa and Hodaka. Or, companies such as Cycle Products West, who make rectangular swingarms will "also build a custom swingarm for any bike for $22.95."
It would seem to me that anyone today could legally have a square or rectangular swingarm on any Pre '75 bike.
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The Swingarm I'm building could have been made in 77.
The reason I'm useing an 80's arm is one I found it at the tip so the price is correct. About the only parts I'm really useing from it are the pivot's and the RHS arms themselfs. I cut and shut it so much you could never guess where it started from. I will run it at CD8 and keep the standard one maybe run it at the Nats.
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The Swingarm I'm building could have been made in 77.
Someone could have made a 2011 CRF450 back in 1977 too...
Its very easy to gloss over improvements in technology.
Either the swingarm is going to make you faster, or there's no point in having it on a race bike.
Either it matters (and you're giving yourself a performance improvement that wasn't available in the day) or it doesn't (and there's no point in getting you knickers in a knot).
Ken, I'd say that you'd be restricted to making the 2011 "replica" arm from materials that were used back in the day - including the dimensions of the RHS.
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The Swingarm I'm building could have been made in 77.
About the only parts I'm really useing from it are the pivot's and the RHS arms themselfs. I cut and shut it so much you could never guess where it started from.
I think it is not that you could have made it in the day, but did someone make it in the day ..... I have a bike with modified 81 cr450 RC replica swing arm, it looks cool but no way it is pre 80 eligible. But hey spray it black when you are finished, time honored way or making modified parts disappear.
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Should that be gloss black or matt black? ;D
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Some DG catalogs here
http://www.vintagefactory.com/vintage_aftermarket_mx_catalogs.htm
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nice one lieth, shows Dg used profabs rouinds even up till 76 so no way its pre 75
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It would seem to me that anyone today could legally have a square or rectangular swingarm on any Pre '75 bike.
I agree, as long as you can prove that the particular design originated prior to Dec 31 1974. I've been on this soapbox so many times it's starting to creak but I maintain that the swingarm is a major component of the bike so therefore must have a period precedent. If DG swingarms didn't appear prior to 1975 then they shouldn't be allowed in pre '75 and Slakewells Kato arm is unfortunately in the same pickle.
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The Redline box section arms Ken is talking about from '74 were chromoly not alluminium. I have all the old MXA mags from the era and DG didn't start advertising box section alloy arms till the '76 models arrived.
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I have a DG full page add in a sept 74' "Dirtbike" for swingarms called the "swinger" for honda, kawa ,suz, 125 and 250 all are round 4130 cro-mo with full gusset :)
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From a Penton/KTM Forum: Found here : http://www.pentonusa.org/forum/topic.asp?TOPIC_ID=1581&SearchTerms=alloy,swingarm (http://www.pentonusa.org/forum/topic.asp?TOPIC_ID=1581&SearchTerms=alloy,swingarm)
"Monty, Glenn, metalkfab, Rob
Thanks for your interest and quick replies.
AHRMA Eligibility .... both "DG" and "Crossup" had aluminum swing arms "pre 74" .... I have photos.
Rob ... thanks for the compliment ... we spent 6 months in design and test. Also, please read through the web site pages ... there are options for bearing materials from hard aircraft quality nylon to needle bearings.
As for the shock mount it was designed to allow for custom location. Shock mount location flexibility was one of the "must have" design features for our swingarm products.
Currently we do not have a design to incorporate multiple holes along the swingarm. However is the interest and commitment ($$$$) are there VMXpert is ready.
Again thanks ... I hope this info helps
TBC (to be continued)
Dom
VMXpert PP
Dom
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The swing arm Im building is for my hot rod 77 so I'm not going to try for pre 74 here, I will keep a original for when and if I ride the nats.
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The '74.5 swingarm is basically the same as the '77 but mounting points for shocks and strengthening webs. You can use the '79 Alloy swingarm, just mounts in, but your shock positions will have to move, same motor and frame dims, so fits.
Adrian
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The '74.5 swingarm is basically the same as the '77 but mounting points for shocks and strengthening webs. You can use the '79 Alloy swingarm, just mounts in, but your shock positions will have to move, same motor and frame dims, so fits.
Adrian
I looked at the 79 and I have seen one fitted to a 77 but there straight without Banana bend so they increase wheel travel allot and then change the whole geometry. I love the way the 77 ride and handle so I don't want to muck with that much.