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New monoshock

Discussion in 'The Garage' started by nickklugs, Aug 13, 2016.

  1. nickklugs

    nickklugs Seems legit

    I have a 76' xs360 that I am making into a scrambler/dual sport machine. I have a swing arm from a 93' KX250 and the stock shock that came with it is about 18" long and that just doesn't fit... at all.

    So I need a shock that's about 15" or 380mm or something around that size, does anyone have any suggestions? It needs to have the clevis end on the bottom to mount on the swing arm.
    Also this is (as always) a budget build so as cheap as I can get would be great <$100

    Thanks a lot,

    I was thinking something like this and just use one of them: http://www.ebay.com/itm/15-380mm-Mo...ash=item1a17e064a4:g:cKUAAOSwjXRXauA0&vxp=mtr It says 660lb a pair so one 300lb shock should be enough right? Or would that be just way to weak.
    Last edited: Aug 13, 2016
  2. Having those shocks on my wife's xs I wouldn't use them for a monoshock. They are just too soft.

    There is a spreadsheet online somewhere of different shock lengths (I'll try to find it) which you can use and then Google or eBay them to find out if it has a clevis mount.

    There is a science to the suspension though so know that there is more to it than just picking the right length and mount type.
  3. nickklugs

    nickklugs Seems legit

    Alright. Thank you. Yeah I am thinking of using an r6 shock possibly.
  4. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Scrambler, no problem. Dual Sport, not as easy. There is a big difference in requirements between riding a gravel road and riding off road. I'm the last person who would say it can't be done. But I may be one of the first to question if it should be done. :shrug: Take a look at advrider.com's "some assembly required" section to see examples of what people are going through to do swaps.

    I'd be inclined to try making the original KX parts work in your frame, so that you have a better chance of success. I'm fairly certain that the KX rear spring will be too soft. It took me about 4 (12+ hr) days to measure and mock-up my suspension swap. I lost count of how many times I tack welded brackets into place, mounted the suspension (with no spring on the shock), moved the suspension through the full range of travel, found a clearance issue, disassembled it, cut the brackets free, measured and re-tacked the brackets, and repeated... :banghead: Be aware that the chain may foul the engine, frame and swing arm pivot at the ends of the suspension travel, so that may limit the suspension travel. The rear brake will also be a concern if you are keeping the stock setup. It took me another full day to get the rear brake and linkage all sorted out, but I'm still not pleased with it 3 years later. It works well enough, but... :cautious:

    If you can't use the original KX shock, you are going to have to do a lot more than guessing if you want to actually ride the bike without problems. Find out what the ratios are for the suspension. Determine the desired ride height and suspension travel (hint: don't differ too far from stock XS height or you will be changing the front geometry, among other things). Then you can start doing calculations to determine the required shock length and travel, required spring length and rate, compression and rebound damping of the shock, linkage length, etc. :umm:

    Also, what are your plans for the front suspension? At a minimum, you should add more preload to the fork springs to reduce static sag. That will help keep the front up and rake and trail changes within reason. Longer forks to match the rear suspension travel and height would be preferred, but that is another discussion...

    Good luck and have fun!
  5. nickklugs

    nickklugs Seems legit

    Thank you a lot. That's a lot of useful info. I may have to do some more research :shootme: As for the front end I am using the stock inverted forks from the KX. I am gonna chop the head tube off the KX and weld it onto the xs maybe... I might try and get custom bearings, but I would need to add a spacer. So yeah.
  6. nickklugs

    nickklugs Seems legit

  7. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Unless you have a frame jig - which I highly doubt, forget about cutting the frame! Beyond the fact that head tubes are highly stressed, and precisely aligned, they also have the bikes VIN and the required certification stickers. You don't want to get the bike completed and not be able to pass inspection, get plates or insurance for it. There are ways to modify the triple trees to fit. From bearings and spacers, to machining a new stem.

    As one could expect, forums often have hard to find information. Find a forum that is dedicated to your donor bike and spend a couple days searching there. You will have to determine what you want the ride height and suspension travel of your bike to be. Maybe it is time to formulate a plan for your bike? Before you go spending, cutting, and welding? You might (probably will) find that you'd be further ahead to buy the bike you want and sell yours to help finance it.
  8. nickklugs

    nickklugs Seems legit

    image.jpeg Well you are correct about me not having a frame jig, but my friends dad does have a machine shop so I think I will be doing some work to make the stock head tube and triple clamps fit together. Infact all I really need is a spacer and the stem to be modified a little bit and it would work.

    And about the vin, the frame I bought is out of the system and has no backfee's or anything. The guy I bought it from said it would be $61 for a new title so that would be better then what I have now. (600+ in backfee's and still registered to a guy upstate) <- that said it was $40 and it ran great with a carb clean and the ignition timed.

    For $100 the KX frame with two sets of forks a rear shock and swing arm it with rear wheel was an offer I couldn't refuse. And besides, I think it looks pretty cool all mocked up...
  9. nickklugs

    nickklugs Seems legit

    P.S. Thank you a ton, those replies were very useful and made me not make any big stupid mistakes.
  10. nickklugs

    nickklugs Seems legit

    P.P.S. I figured out a way to use the stock shock by tilting the bike back a bit and raising the tank. I am also going to to fabricate my own new subframe. So it should be pretty cool. I also have the subframe that came with the KX frame so when all else fails I can bolt that one on.
  11. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Glad to be able to offer some advice. It sure looks like a fun project! Consider starting a build thread and documenting your progress. I was rushed and didn't get a single progress picture when I did my modifications.
  12. nickklugs

    nickklugs Seems legit

    I'll try :thumbsup:

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