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Drag Racing 1978 Suzuki TS185 Nostalgia Bike

Discussion in 'Motorcycle Racing and Track Days' started by Frankster, Mar 22, 2020.

  1. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Ok, maybe I've got the caster (trail) thing backwards. Give it a try and be careful.
    Also, if you weld a plate to the bottom of the frame you will have to remove the engine to change the clutch cable.
    Try here for aftermarket as the prices asked for original Yamaha bits is getting past a joke. Check that the flywheel has the correct number.
    https://www.ebay.com/itm/Yamaha-DT2...901969?hash=item2ce903cf11:g:E64AAOSwF-Jaz6su
    This for a full kit including the lighting. Ask them what a basic ignition only kit will cost.
     
  2. Andych

    Andych Well-Known Member Premium Member

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    If you want to calculate the trail in both configurations then this site comes in handy... although you need to convert everything back to inches..
    https://www.rbracing-rsr.com/rakeandtrail.html

    The lower the Trail the more "nimble" the handling.. the longer the trail the better it is for stability in a straight line (within reason of course) ... this will also change if you change the rake of the bike as the rake of the bike changes... the same if you lower the front end... the effective length of the forks changes relative to the top of the triple tree...
    Interesting to play around and see what the various changes do.. when I was looking at different front end configurations for the SRX I made myself up a quick spreadsheet that converted my metric measurements to inches so it was quick and easy to do lots of different combinations.
     
  3. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Also, if you weld a plate to the bottom of the frame you will have to remove the engine to change the clutch cable.

    Yes, I saw that the DT250 clutch cable connects under the engine. I was thinking of trying to find a way to access the lever without getting the engine out. I think some engine/stone guards have a hole in them for access to oil drain plugs, so maybe do something like that if I put a plate in the bottom. I don't want to overthink this project too much. I'll be more than happy if the new tyres fix the head shake, so I can then get onto the engine.
     
  4. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Looking at the numbers for the offset - currently trail is at 106mm - reversing those fork clamps will add ~43.5mm to the trail because it reverses the offset from +24mm to minus 24mm and the cosine of that 48mm change is 43.5mm - so total trail should increase to 149mm

    I used the assumption of a a rake angle of 25 degrees
     
    Last edited: Mar 24, 2020 at 9:12 AM
  5. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Thanks Andy. As I only intend to race this thing in a straight line, my main goal is stability. If it had 200hp, then I'd have to factor in squat, traction, wheelstands etc. If you look at any purpose-built drag bike you'll notice they all have a severe rake on their front ends. They run steering dampers only because the rules say they have to. Even when they put the front wheel down after a wheelie the bike doesn't shake it's head and the bike continues to go in the direction it is pointing. This is regardless of the angle of the front wheel when it makes contact with the ground. The extreme rake makes steering almost impossible under acceleration. These are all things I will not have to worry about.
     
  6. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    That's exactly right Ruckus. 149mm is a lot of trail, so should be seriously stable, plus I haven't changed the rake so should still go around a corner without pitching me into the weeds. All theory at the moment. Looking to get those new tyres on and seeing what effect they have on the bike. Steering head stems ordered, so they'll be my next change.
     
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  7. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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  8. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    I think by the look of it that is ALL you need - that is something that I was searching for last night, not knowing if such a thing actually existed, not cheap, but it also gives you an advance curve, that should be an improvement over a static advance throughout the entire rev range
     
  9. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    If the rear shocks have raised the rear end up, that will effect geomtry at the front. Stuffed steering bearings can cause head shake or a weave to develop when riding in a straight line along with difficult turning from running straight. If the front is lifting as well this can cause bad tank slappers.
     
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  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The DT250 1974-1978 ignition condensor is made by Diiachi Japan, part number 654-81325-20 (can subtitute 183-81326-10 too)
    the same condensor is also used on Honda 71,72 CT70's, 1971-1973 SL70's and the 1974 XL70 part number 30250-035-006 (can subtitute 30250-001-000 / 30250-041-006 too)

    They measure .27uF - .33uF (@20° C) but you'll need a capacitance meter to measure it


    I was chasing an electrical/ignition fault in a mate's 1976 SP370 Suzuki a couple of year's ago and found the condensor had failed and shorted to earth
    I couldn't find an oem or aftermarket one in Australia so ended up going up to the local self serve wrecker's and looking through some car's.
    Found that the 1980-1984 Ford Econovan used the same size condensor and all i had to do was swap the terminal type on the end of the wire to make it work, bought it for $2
    If you're lucky you can find one with the capacity stamped into the condensor body to make it easy to identify

    [​IMG]
     
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  11. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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  12. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    You can visually determine if a condenser if kaput by watching the spark through the points while it's running if there's a splatter of sparks like a tiny firework then it's gone, it should be one single distinct spark
     
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  13. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    The Rex's Speed shop CDI conversion will give better and hotter sparks than a standard Yamaha set up, and is adjustable for timing. The kit will be all you need.
    Again, the frame and suspension is STANDARD Suzuki. There is no longer shocks or different wheels, it is just as it left the Suzuki factory as a trail bike.:mad:
     
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  14. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Again, the frame and suspension is STANDARD Suzuki. There is no longer shocks or different wheels, it is just as it left the Suzuki factory as a trail bike.

    Yes. I'm not saying they are different. First pic is where the chain was attacking the frame. Second pic is the chain laid out as suggested. I couldn't see any twisting or high spots. It's very dirty, but a bit of Kero will solve that. It has 2 master links in the chain, but that shouldn't make any difference? Not sure why this chain was smashing into everything around it.

    IMG_0639.JPG

    IMG_0633.JPG
     
  15. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Are you able to check the suggestions of @my67xr for worn bushes or bearings in the swingarm, looks to be definite movement there
     
  16. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    The Rex's Speed shop CDI conversion will give better and hotter sparks than a standard Yamaha set up, and is adjustable for timing. The kit will be all you need.

    So, this is the other flywheel and bits in the box, but I'll wait a while before doing the CDI conversion. As Ruckus said, it's a bit $$$.

    IMG_0628.JPG
     
    Last edited: Mar 24, 2020 at 8:33 PM
  17. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Well, there is definitely a LOT of movement somewhere. As I previously stated, this thing vibrates like a jack hammer. The Swingarm bushes actually look and feel not too bad. Engine mount rubbers are not good and the bolts don't fit properly as there is about 2mm of play in all the engine mounting orifices.

    I haven't had a twin shock rear end for a very long time and I can't recall if the shocks are meant to move? These you can turn by hand, so they're not tight on their mounts. I might post some more pics tomorrow as there are a few bits on the frame that look like they've been added on. There's also the area around the custom engine mounts for the DT250 engine that I need to confirm the changes with @Murdo

    IMG_0634.JPG IMG_0635.JPG IMG_0636.JPG
     
  18. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Lucky last post for the night. The bike is down to the frame now, so when tyres arrive, I'll get stuck into putting it all back together.

    Frame 20200324.JPG Frame 20200324 2.JPG
     
  19. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Trying to think where you might get a range of polyurethane bushes or material to make them, but what about the hydraulic hose that @Murdo cleverly employed to take up the space in the clutch basket on his little ZZR250, perhaps a combination of hydraulic and radiatior hoses

    Get some small lengths with some which perhaps telescope to get nice tight fittings on all of those bolts, it may not have been the swingarm twisting but the engine moving under acceleration making the chain swerve and fling about
     
  20. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    YZ250D specs and airbox/filter. Looks like the original bike ran a 36mm carb. I'll have to check this carb tomorrow, but I do seem to recall @Murdo saying it was a 38mm. The main jet size on this spec seems much larger than what we're running. They're running 20:1 premix, we're running 50:1 (98/full Syn).

    YZ250D Specs.JPG YZ250D Air Filter.JPG
     
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