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Swing Arm Extensions For '74 Ty250?


thats_a_five
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Here is info from a couple more bikes from my collection. I hope I don't add another level of compexity to the discussio but I noted one other significant difference when I was measuring - swingarm length - so I am adding that also.

'74 Yamaha TY250 51" 29% Swingarm 15"

'85 Honda TLR200 52" 29% Swingarm 18"

'94 Gas Gas JT25 53" 33% Swingarm 20.7"

I am not a suspension engineer but I think I see a trend here.

Related to this is the location of the swingarm pivot. The TY250 pivot is only slightly in front of the pegs. The TLR and the JT swingarms pivot 3 to 4" in front of the pegs. Can't change that because of the length of the engine.

For those who lengthened their TY175's how did it change the riding characteristics?

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I am not a suspension engineer but I think I see a trend here.

Related to this is the location of the swingarm pivot. The TY250 pivot is only slightly in front of the pegs. The TLR and the JT swingarms pivot 3 to 4" in front of the pegs. Can't change that because of the length of the engine.

Yes there is an obvious trend - motors were developed over time to be shorter so the swingarm could be made longer

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  • 8 months later...

Update.

Wow, I didn't realize how long it has been since I started this thread. I finally got to add the extensions to my swing arm. Actually, I picked up a second swing arm so I now have both the standard and longer one.

I cut off the old ends and added the extension pieces I bought from Shedworks. Also cut off and rewelded the mount for the brake plate rod. I think this added 1.5" to the length. Installed longer chain.

Rode for a couple miles last weekend and it seemed to work much better. More compliant, less twitchy. Also better for starting from a stop going uphill. It definitely made the front end feel heavier as expected. Overall, I am happy with the change.

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  • 5 years later...
On 12/8/2012 at 3:48 PM, b40rt said:

1980 SWM standard 52.5" 28.6%

1987 Aprilia standard 51.5" 28%

1982 SWM modified footrests 53" 25.5%

@feetupfun @pmkk parallel topic 're footrest position. The 87 Aprilia has had the footrest moved down and back since above, the percentage has dropped to 25% . Bike feels more "planted"  The top yoke has been changed to txr with risers, now much more comfortable with no downsides.

 

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