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Project Suzuki Across Engine Swap

Discussion in 'Your 250cc Projects' started by Jethalter, Apr 1, 2019.

  1. Jethalter

    Jethalter Well-Known Member

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    So i figured i'd post this here, Since i've got a GSF400 VC Bandit engine i want to shoehorn into an across frame.

    This is a spare rolling frame i have, if it works out well i'll probably build the bike and source a new front end and some fairings and such for it. The other option if it does work out well is i can simply just do the mod on my current across and leave the rebuilt across motor for another across i come by.

    Anyway the facts on the engine swap.

    The rear mounts , top and bottom are correct heights to suit the engine. Both mounts have engine sit hard against the LH side (if your sitting on the bike, Left Hand) This also lines the sprocket up correctly. The bottom RH mount is in a fine position but the case is narrower, so this requires a spacer. The upper RH mount is too narrow, so this has to be cut off the frame and moved over.

    Now as far as the engine moving up in the frame, the main frame rails on left and right side are approx 25mm too narrow to allow the gigantic GSF400 head to pass through. So these rails will have to be modified.

    At the moment i'm working on the best way of widening the frame.

    Pics to come sometime.
     
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    Last edited: Apr 1, 2019
  2. Jethalter

    Jethalter Well-Known Member

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    Just doing some figures on the pricing of steel to do the frame and to build a jig to do it all.
    I've got a lead on a bandit 250 that could potentially work for the swap, so whichever will come in cheaper i think will the be the option.
    Its doable on the across, the fairings have enough gap in them to allow for the wide rails, but so far it isnt very cost effective option.
     
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  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    How much does the 400cc engine weigh?
    Moving it up in the frame will raise the centre of gravity a bit, and make the bike feel top heavy
     
  4. ShaneP

    ShaneP Well-Known Member

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    Why not put fairings on the 400 bandit? I'm not sure the across frame is worth it.
     
  5. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I would have thought that the cost of having it "Engineered" would discount it from happening at all.. As @my67xr mentioned with regard to the C of G you could end up with a very poor handling bike that cant be registered and potentially would be dangerous.
    There are far better bike projects around to spend your hard earned $$ on I would have thought...
     
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  6. Jethalter

    Jethalter Well-Known Member

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    I have an engine, not a 400 frame. Find me a 400 frame, they simply ain't about. And i've got to do something with this engine.

    Its not moving it up the frame, it sits in the same position as the across motor. Granted you will add a bit of weight on the top of the motor with the larger head, its sfa, that will make no difference. You have 6mm larger bore and 7mm more stroke on the 400 vs the 250.
    The weight of both the across motor and the 400 motor is sfa between them. I haven't measured on a scale, but i can lift both fairly easily by hand. I cant do that on my gt550 motor.

    Really not interested in bs about it, engineering cost isnt that great, you just need to know the right engineer who won't tear you a new butthole. It ain't more dangerous than half the people who were given driver licenses in the past 10 years.
    If done correctly, it would be far superior to standard. Also get that the engine acts as a stress member in the frames, its what gives them strength.
     
  7. Jethalter

    Jethalter Well-Known Member

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    checked out a couple of bandit 250s today, it has a better chance of fitting in the across so thats the plan. i know how to fabricate the new frame sections, its just a matter of finding the right equipment to use to do the curvature without using heat.
     
  8. Murdo

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

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    Bottle jack and a couple of pieces of wood?
     
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  9. Jethalter

    Jethalter Well-Known Member

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    Nope that ain't gonna work.

    Another note tho, i also got to check out a gs500, and that sucker is tall, i'd dare say even way to tall for the across frame. Probably hit the cross bar at the front.
     
  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I thought you had to widen the frame so the gigantic head could fit in between it ?
    So i though the head was bigger and would weigh more?
    Piston's would be bigger, rod's bigger, crank bigger etc etc
     
  11. Jethalter

    Jethalter Well-Known Member

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    Correct on all, but the weight difference is sfa apart from the head. And even then, the head isn't that heavy. If i was to guess saying the across motor is 40kg, the 400 might be 45/50 at the most.
    I should have posted a pic to make sense of what move up meant, since the engine is tilted down cause it won't quite fit in between the rails. I'll look through an find a pic to explain it better.
     
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  12. Jethalter

    Jethalter Well-Known Member

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    I should also add, that the non VC motor, would have much better chance of fitting, the point i reckon you could squeeze it in without mods. The biggest problem with the VC motor you see is the caps near the camshafts, they stick out 17.5mm from each side of the head to which i can get it down to about 15/16mm by using button head bolts instead of cap head bolts.

    Anyway here is the pic i was referring to of how i meant about moving the motor up. This is also in my spare frame.
    So the idea is i will rebuild a whole another frame rail to go from the twin rails at the front, all the way onto the swing arm plate. If done correctly this should still be fine for the strength and i'll remove the inner/top/bottom of the original rail leaving the outer skin, so in theory whilst only a vertical wall i'm never actually cutting the frame into two pieces.
    Thats the idea im following with at the moment. If its done like so, unless you really really know the across, you won't even know its done.
    I'm still taking my time and not rushing to quickly as i might have better ideas come about. One way or another whilst i have the engine in my possession, it will be going in that frame.

    Hope it gives you a bit more of an idea.

    IMG20190401164102.jpg
     
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    Last edited: Apr 2, 2019
  13. Jethalter

    Jethalter Well-Known Member

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    Here are the two main problem points.
    The right circle is the first bend in the frame, thats where it hits the head and stop its rotating into position.
    The left circle is going to be an area i imagine once the engine is in position that the carbs are most likely going to hit.
    IMG20190401164102-Copy.jpg
     
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  14. Jethalter

    Jethalter Well-Known Member

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    I have checked clearances with the fairings, i have 1 inch per side along those rails before hitting the fairing.
    The suzuki clutch cover, where the writing is, does hit the fairing and will have to be cutout for it.
     
  15. Jethalter

    Jethalter Well-Known Member

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    Since im waiting on parts for my other across engine still, and i've got a great big tractor in my shed awaiting parts i thought i'd tinker with this some more.

    Today i build a frame brace/jig for it, just what scrap steel i had about. I also cleaned both frame rails and got the plate tacked on the frame rail. Tomorrow i'll sort out the rest of that plate then its the proper frame tubes going on. once thats done it will be remove brace/jig and start seeing what of the original rails needs removal for the motor.

    This is basically a proof of concept, cheap quick easy way to see if its going to work. If the motor fits in and everything else works out i'll be getting another frame that i can actually club reg for it. Since 2 cars and a bike already on full reg is enough.
     
    Last edited: Apr 21, 2019
  16. Jethalter

    Jethalter Well-Known Member

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    So widened the frame, fit the engine, still got many other issues that widening the frame dont solve.:(
    So atm this is going on the back burner (its a frame i dont really care about anyway).
    Plan is when i get my genuine stem seals to finish the across motor and put my other bike together, as well as finish off the GT550 i'm building, once i get those two out of the way i'll build a proper Motorcycle JIG, separate the stem and the rear frame/swing arm section, then bolt the motor in and build the frame tubes around that. Only possible way it will all work.

    Even if it was a non VC motor, it still wouldn't fit, head is too large without doing listed above.

    It will get done at some point, just not as quickly as i'd like.

    Looking into the differences between ERW/DOM tubing, I think for what im doing ERW will be fine since over the small section that it is flex isn't an issue and its actually stronger that DOM in small sections.
     
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  17. Jethalter

    Jethalter Well-Known Member

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    So i started a side project to help sort this 400 across idea out. It set me back a week on building my other across motor but i'd rather start and finish something then move on rather than have more unfinished stuff there.

    I built this to do the 400. I still need to fabricate the neck stem and cones for it, but i have everything there to do so.
    This should make it a bit easier to get sorted.

    Its all dead level, uprights are 90 degrees, the main horizontal beams are 0 degrees, when you rotate the main jig 180, its 0 degrees still.

    IMG20190509122429.jpg
    IMG20190509122439.jpg
    IMG20190509122447.jpg
     
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  18. Jethalter

    Jethalter Well-Known Member

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    Today had a bit of spare time, put the frame on the jig, need to get the tubes sorted to centralize the swingarm and make the brackets to bolt to the bottom middle part of the frame. But all in all its getting there.

    Should make it interesting to see. I'm still a bit hesitant to cut the stem away from the frame completely, it shouldn't be a problem, im just a touchy about it. One i make up the other bits and have it completely bolted. I'll take measurements of certain points of the frame then probably cut one side off completely and cut out as much as i need on the other side to get the engine to fit. Then i'll remake one side tubes and then copy them for the other side, tack them in place, and remeasure it all.

    Anyway main point is progress being made. What seemed so close of a fit (it literally was) has shown a few more issues that go beyond normal.

    My god, that fuel tank is a pita, what a pain in the ass to get out.
    I think with the 400 i'll loose most of my trunk space, room for carbs/airbox(pods), battery and such. Will be a shame but will see what i can retain.

    The tank with this frame is rusted as hell, so its scrap. Def will have to remake a tank to suit, I'm tempted to do a few things but will wait and see, anything to get a couple litres more fuel with a larger engine will be a good thing.
     
    Last edited: May 28, 2019
  19. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Looks like this one
    chop_source_full_frame_jig_with_rotisserie_stand.jpg
     
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  20. Jethalter

    Jethalter Well-Known Member

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    It is very similar, some differences tho. I didnt get anything from them for it tho.
    Its also done for metric bolts and steel.

    And their cones for the neck stem are too small for the across also.
     
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