Installing VFR750 Swingarm in a project....looking for some info

Discussion in 'Mechanics Garage' started by tukn20s, Jan 28, 2013.

  1. tukn20s

    tukn20s New Member

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    I'm going to be installing a 94 vfr750 swingarm and rear suspension in a project bike I am building. I have to do a small amount of machining to the arm so it will fit in the slightly narrower frame. I want to take equal amounts of material from either side of the arm to maintain centering of the wheel. I'm trying to get the original mounting and spacing figured out but I only have parts to go off and not an actual bike. What I'm trying to determine is if there is any spacing between the frame and swingarm on the right side. I know that the bushing (#9) on the left side creates about 3-3.5 mm of spacing on that side. Does part #10 or the axle itself, space the arm on the right or does it rest directly on the frame.

    vfr750 swingarm.jpg

    Also, I assume it would be best to keep the original geometry of the suspension so that it works properly. Does anyone know the angle between the shock and the swingarm?
     
    Last edited: Feb 2, 2013
  2. Mohawk

    Mohawk New Member

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    I think you might need to rethink your adjustment method. The wheel is NOT central to the swingarm bearings ! The left side is critical for chain allignment, so make sure you get that side accurate first. If you have the rear hub & wheel, then attach them to the swingarm & work out where the wheel centre is in relation to the pivot point. Many frames are NOT symetrical & often the middle is NOT the centre line ! The VFR's have approx 18-20m offset & raceteams have increased this to 30mm for wider wheels with NO adjustment to the swingarm with no apparent bad handling issues. Obviously get the centreline as accurate as you can but 1-2mm makes no detectable difference to the handling.
     
  3. jethro911

    jethro911 Member

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    Really!?
    I'm not a frame guy but these number seem extreem. I'm also not calling "bullshit" because I don't have the data or experience to know. My gut is saying that the tires should track in line so the bike turns left and right the same and the sprocket / chain alignment should be modified to allow the tires to do so. But that is just my gut. I'm not a frame builder.
     
  4. Mohawk

    Mohawk New Member

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    Maybe that did not come over correctly. The centre of the frame pivot on the VFR swingarm is NOT the wheeel centre line. The wheel offset is how far the mounting face is off centre from the wheel centre line, these are wholly different measurements. Hence the advice to mount the wheel & determine from it where on the swingarm frame pivot the actual centre line is ! The 30mm race offset is only 10mm right of centre & was used on RC30's etc quite alot to allow them to run wider tyres !
    Many normal bikes have over the years had the rear wheel allignment markers wrong & people have ridden them for years & not noted any difference in handling side to side, likewise 4-1 exhausts usually upset the balance of bikes & most people just compensate automatically, no big deal.

    When mounted on the VFR, the VFR swingarm holds the wheel centrally, that does not mean it will just drop into any other frame & hold the wheel central in that frame !
    So no not bull, just facts that he needs to take into account. Shaving equal amounts off both ends of the frame pivot on the swingarm will NOT necessarily place the wheel on the centre line of the guys application !
     
  5. TOE CUTTER

    TOE CUTTER Mullet Man

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  6. tukn20s

    tukn20s New Member

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    Thanks for the input so far. Some good issues for consideration were brought up. I will absolutley be checking the center alignment before any thing is modified on the arm. Right now I'm just trying to gather some information and come up with options and a gameplan. I've talked with several people who have done the swap in similar frames and center alignment was not an issue....again not something i'm just going to assume.

    So then is the vfr swingarm mounted off-center in the frame?

    As jethro mentioned, I think it will be best to center the wheel and then adjust chains and sprockets from there. Its very unlikely that the sprockets will line up anyway.
     
  7. JamieDaugherty

    JamieDaugherty New Member

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    Yes, all swingarms are. The problem is they are not offset the same amount from bike to bike, which is in a nutshell what you are being told here in this thread. Jethro is right on the money: you have to center the wheel and make everything else fit around it. Most often this requires a TON of work (machining, fabricating, etc). It is so much work that most of the time when you see a swap like this it was not done. I've only ever seen a couple of bikes that were done correctly, so it is very rare but can be done.

    Good luck!
     
  8. NorcalBoy

    NorcalBoy Member

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    the main things are that the front/rear wheels and front/rear sprockets are on the exact same hoirzonal centerline and that the swingarm downslope angle is correct. Also to be considered is the distance of the swingarm pivot from the countershaft.......
     
  9. tukn20s

    tukn20s New Member

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    It looks like the wheel is off-center from the pivot centerline by about 3-6mm. I still need to check chain clearance, but otherwise this shouldn't be too much of an issue. I will get a more accurate measurement when I get to that point.

    As for the factory bushing setup, does anyone have any insight with that? Or the width of the frame at the pivot point would probably work as well.
     
  10. tukn20s

    tukn20s New Member

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    This was something else I was trying to determine. If anyone knows this angle as well as the angle between the shock/swingarm that would be awesome. I don't have the a VFR frame to measure from.

    Thanks for all the info so far everyone!
     
  11. NorcalBoy

    NorcalBoy Member

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    This can be determind after you get the pieces assembled and aligned correctly. The best way to determine this is to have the assembled bike, sans bodywork, put on a GMD Computrack jig and have all of the pertinent geometry points measured and evaluated. GMD will take the measurements, plug them into their database, and provide you with the "sweet numbers" for the chassis. At that point, you can determine the best route to achieve the best geometry, i.e. swingarm downslope angle, ride heights front and rear, rake and trail. They will recommend the optons that you can implement. They will also be able to confirm that everything is properly aligned, i.e. headstock to swingarm pivot, headstock to axle, front wheel centerline to rear wheel centerline, if the rim is truly perpendicular to the axle etc....most folks just bolt everything together and say its aligned, reality is that it is't.....a couple mm here and a couple mm there, adds up to a less than fully functional package. For some, just slapping on a homemade subframe, or grafting a swingarm onto a donor main frame is acceptable. It's a matter of perspective.
     
    Last edited: Feb 2, 2013
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