Vintage Dirt Bike Q & A
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'79 swingarm advice
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Author:  bultokid [ Tue Sep 30, 2008 12:48 pm ]
Post subject:  '79 swingarm advice
First off as a newbie to Red Rockets this site has been a incredible wealth of knowledge, a big thank you to all. I raced my '79 CR250 for first time past weekend and all I can say is I now know why my beloved Spanish bikes went belly up. I've searched the site and answered numerous questions but still a little foggy on swingarms. I have '43mm KYB off a '82 480 set-up dead on for me and stock arm with set of sweet 17.5" Works triple rate p/l adjustable shocks spot-on suspension is great. Really just want the arm for that "works" look and have read some have rising rate vs failing but I just want a true bolt on with no mods needed. Thank you in advance
Author:  dogger315 [ Tue Sep 30, 2008 6:58 pm ]
Post subject:  Re: '79 swingarm advice
I read your post a couple of times and I think you are asking if anyone sells a
direct replacement aluminum swingarm for your bike. If that's the case, you
can get one from AMS (check the resources icon).

Rising and falling rates usually pertain to linkage equipped suspensions and is
a function of eccentricity due to link length and pivot points. The only non
linear action (rate change) you will have with a twin shock setup that I can
think of, is the increased resistance provided as your progressive shock
springs compress.

Hope this helps.

dogger
Author:  bultokid [ Tue Sep 30, 2008 8:54 pm ]
Post subject:  Re: '79 swingarm advice
Dogger, thought I had read on post somewhere on here that the banana shaped arm gave a rising rate ratio maybe I misunderstood. I should have worded it better as what I really want is a arm to fit mine that will use the stock length shocks and bolt up with no mods and not sure if that is the Fox or DG or what. Thanks for all the help I can't say thanks enough.
Author:  dogger315 [ Wed Oct 01, 2008 9:35 am ]
Post subject:  Re: '79 swingarm advice
bultokid, that is a good possibility with an eccentric shaped (banana) swingarm,
good point - I learn something new everyday :o

As for your requirements, Fox and DG made direct replacement swingarm back in the
day but I don't know how easy it will be to find one now and I don't know if anyone
is selling repros for the '78/79s, maybe one of the active vintage racers on here can
chime in.

The swingarm that AMS sells is a Thor and is a direct replacement, no mods required
bolt on that looks like the Fox and DG offerings. At $450, it's not cheap but it probably
cost a lot to produce. You can also post a wanted add on the swap meet section of
this forum. I have had very good results with that, there are a number of folks on
here that have been a big help to me and others - worth a try.

dogger
Author:  hrc21 [ Wed Oct 01, 2008 1:05 pm ]
Post subject:  Re: '79 swingarm advice
Have a look on http://www.cyclestopracing.com They have a nice looking aluminum swingarm listed for 78-80 red rockets.
Author:  redrocket190 [ Thu Oct 02, 2008 4:30 pm ]
Post subject:  Re: '79 swingarm advice
If you want to preserve the existing shock length, geometry and setup go with the straight Thor or DG-style. I expect the arm to be the same length as the 1980 which is about 1" longer than the 1979. More stability. You can raise your forks a little to compensate.
Author:  FTE [ Thu Oct 02, 2008 4:36 pm ]
Post subject:  Re: '79 swingarm advice
Novation racing has a beautiful swingarm for a bit more than 500 and they do them with stock geometry for the 79 or 80 and also an arm that tracks the Fox geometry (the photo below is not my bike, but it shows the banana version). They recently said the lead time is about six weeks after order.
Image
Author:  redrocket190 [ Fri Oct 03, 2008 4:54 pm ]
Post subject:  Re: '79 swingarm advice
That's very cool. I had been under the impression the Novation arm meant you had to get new shorter shocks....
Author:  bultokid [ Sat Oct 04, 2008 7:13 am ]
Post subject:  Re: '79 swingarm advice
Thanks for all the great replies. Good info
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