Vintage Suzuki Dirt Mongrel

Discussion in 'Some Assembly Required' started by cedric, Jan 22, 2021.

  1. cedric

    cedric Been here awhile

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    I'm looking for some advice from the collective here on which way to go with my project. It all started about a year ago with a free 1993 RM250 frame, swingarm and shock. Then I got a PE250 engine and pipe from a friend, but it was in rough shape. I bought a KX500 front end and got that adapted to the RM frame, and also got an RM rear wheel, creating a roller. Realizing that I would need to alter the RM frame cradle to accommodate the side exit exhaust, and also in search of a better engine, I ended up buying a nearly complete '79 PE250 a few weeks ago, which was missing a tank, seat, exhaust and some electrical parts. My original thinking was to graft the frames together, using the PE cradle and rest of the RM frame. It's a significant amount of figuring/cutting/welding with lots of potential to go sideways. I have crap welding equipment/skills, but have access to a friend with some good equipment and a developing skillset. My intention is to have an old school looking/feeling bike that has modernish suspension and brakes, that can be ridden aggressively.

    The PE had some electrical issues, which I was able to sort out and get it running. About this time, I started to think about using the PE as the foundation, and adapting the KX front end and the RM swingarm/wheel/brake, using some Chinese RFY shocks like ShinyRibs did on his XL500. This could be a lot less welding/fab work, but I suspect the end result would not ride as well as using the RM frame. It does sort of maintain the PE heritage, although I'm not a purist and it's not like I would be ruining a nice PE. Using the PE frame solves many headaches, like working out the exhaust pipe, frame mods, intake routing, but introduces some other headaches like figuring out a rear brake pedal/mc mounting, fabbing shock mounts and making the junk shocks work ok. Using the RM frame would probably result in a better handling bike, with better ergonomics and a sturdier frame. I also have a better handle on the paperwork/registration for the PE, while the RM VIN is going to require a bit more creativity and/or process. So I believe using the PE frame will simplify things, but I have to admit that figuring out solutions to the problems can be a big part of the fun for me.

    I don't really have any bodywork for either bike, and I'm expecting to either have to find/build a tank and seat for either frame, and scrounge up some fenders, etc. There aren't really any vintage racing options in my area so meeting vintage rules is not a concern of mine. Just want a bike that is fun and not scary to ride on the steep, rough trails in my riding areas. I don't have a big enough budget to consider restoring the PE to original, and I'm not really interested in that either. Mountain trails and drum brakes just don't work together for me.

    This is going to take me months/years to get done, as I have a full time job, family, and other bikes and hobbies all competing for my time and money. This SAR forum is probably my favorite thing on the internet, for some reason I just love all these custom projects. I really enjoy all the creativity and ingenuity I see on here and really respect all the skills and knowledge you guys have. Any thoughts, what would you do if you were me? Things I should avoid or watch out for?

    Attached Files:

    #1
  2. sruss67

    sruss67 Been here awhile Supporter

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    Seeing as you have spent some time getting the RM frame rolling with the forks etc, maybe it would be the better option to graft the engine to...............
    Thinking the steering angle and wheelbase with the setup on the RM might be friendlier for the type of riding you plan to do.
    Also think it may be easier and less costly getting tank and plastics for the RM than the PE?
    Cool project, should be fun and great learning either way you go Cedric.
    #2
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  3. cedric

    cedric Been here awhile

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    #3
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  4. sruss67

    sruss67 Been here awhile Supporter

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    #4
  5. greasyfatman

    greasyfatman Long timer

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    Rm250 frame low center of gravity pe250 motor. Seams like it would be a better trail bike. Would be really cool if you did a little nav tower wind screen comfortable seat and more gas/luggage and made a long range two stroke adv bike.
    #5
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  6. cedric

    cedric Been here awhile

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    I think at this point I'm going to proceed with trying to get the engine fit into the RM frame. Plan is to try and leave the PE frame intact, and still have that as a fall back plan. Currently it's -15C outside, so too chilly to really spend any time in the garage. One of the challenges with fitting the PE engine in the RM frame is that the RM swingarm bolt is designed to go through a boss at the back of the engine cases, but the PE engine cases do not have such a boss. My plan is to first create a motor mount that occupies the space in the center of the swingarm bolt, this should help ensure that the engine is straight in the frame and will get the drive sprocket in the correct location. May require a few prototypes before I get it the way I want it. Everything else with regards to motor mounting and frame mods will happen after that.
    #6
  7. sruss67

    sruss67 Been here awhile Supporter

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    Bloody hell, -15F is too cold to do anything constructive in. Thought our winters here in Tasmania were cold, got nothing on you up there Cedric.
    Good idea on fabricating an engine mount that links to the swingarm bolt/original mount of the RM frame, should hold everything square/true and provide a solid mount at the same time.
    #7
  8. cedric

    cedric Been here awhile

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    -15F is -26C, it's not that cold now, although we usually get a couple weeks of that each winter. -15C is still cold enough for me to want to lay low.
    #8
  9. cedric

    cedric Been here awhile

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    I dragged the pieces of the "rough" engine into the basement. Plan is to assemble an empty engine shell for mock up purposes. That thing is heavier than it looks.
    #9
  10. cedric

    cedric Been here awhile

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    Finally got the shell engine put together. I'm glad I'm not trying to use this engine, it's pretty rough and had a hard life. Looks like somebody used it for a while with missing/broken steel bushings in the rear motor mounts, which has deformed the casting and in turn kind of negates my intended use for this empty engine. If nothing else I got to practice tearing down this engine and get a feel for which spare parts could be useful and which are toast. It needs a thorough degreasing but is more or less ready to help plan/execute the next step, the rear motor mount.

    Attached Files:

    #10
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  11. cedric

    cedric Been here awhile

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    The RM swingarm pivot is 16.9mm diameter, so I need a 17mm ID sleeve to start my mount. I'm hoping to get lucky and find something suitable off the shelf. So far I've considered wheel bearing spacers from bikes with 17mm axles, but I think the fit will be too loose, they seem to be 17.2mm to allow for easy installation. Another option is another set of swingarm bearing sleeves, but I would rather start with something a bit thicker and a single piece if possible. Any ideas?
    #11
  12. Pezz_gs

    Pezz_gs Cant ride for crap

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    May I make a few suggestions.

    Building a bike like this will take a lot of time and determination

    I put a PE175 motor into an RV125 and it was a lot of finessing to get it right.

    I'm currently shoehorning a DR200 into the RV and we are talking multiple frame cuts and extensions to make it fit

    Can I suggest you make it a bit easier on yourself and use the PE frame with the PE motor .

    Run the RM swingarm and 500 front forks.

    Bushes are readily available. Will the RM swingarm fit in the back of the PE frame?

    It will solve a lot of little things you will have to sort like exhaust you mentioned above

    Sounds like it will be a great project either way :thumb

    8707490C-C1C1-4E0E-BC6F-FE19541A25D9.jpeg
    #12
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  13. tdvt

    tdvt Been here awhile

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    Actual metric tubing seems really hard to find in North America & when you do it is limited in sizes, minimum quantities are big & it is expensive.

    I have come across similar situations & have had good luck with Speedy Metals online selection of DOM tubing. There are lots of wall thicknesses for the various ODs, so with a little digging around you can usually come pretty close, sometimes perfect.

    https://www.speedymetals.com/c-8242-category.aspx



    To make things easier I use this conversion calculator

    http://www.worldwidemetric.com/measurements.html


    Not sure about the shipping situation to Canada but worth looking into
    #13
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  14. cedric

    cedric Been here awhile

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    After a bunch of digging, I've found that a Ninja 600r uses a 17 x 25mm bush in the swingarm pivot that will be plenty long for what I need. I'm going to track one down and see how it looks.

    Appreciate the advice gents, keep it coming. It's really tempting to proceed with the PE frame to keep things easy, and I'm keeping that option open, but sometimes you just gotta jump straight into the deep end and see what happens. I have more time than money for this project and I'm perfectly ok with this taking a couple of years to get done.
    #14
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  15. cedric

    cedric Been here awhile

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    It's not like I'm missing out on any good riding weather...meanwhile you guys are likely sweating your balls off down under. At least the sun is out. IMG_20210210_082025.jpg IMG_20210210_082047.jpg
    #15
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  16. cedric

    cedric Been here awhile

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    Finally did a bit of chopping this evening, the motor needs to be further down in the front so the rear mounts don't foul the shock spring. I may have to remove a few mm off the front edge of the cooling fins to gain some more clearance. Seems like it will be just enough room to make it all work.

    Attached Files:

    #16
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  17. cedric

    cedric Been here awhile

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    Found some time to make up a prototype rear engine mount. Next is to cut it out of steel with some speed holes and cross bracing. IMG_20210616_224437.jpg IMG_20210616_224852.jpg
    #17
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  18. Foxed101

    Foxed101 Monkeywrench

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    Nice HAD (hardboard aided design)!
    Will be following:lurk
    #18
  19. cedric

    cedric Been here awhile

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    1. Had a bit of me time today and with the motor mounts somewhat figured, I took a bit of time to think about how the motor position will affect all the other problems.
    2. The carb will be tight, but I think I can remove some length from the carb easy enough. The pipe will need numerous mods, but that was expected. The proportions looks reasonable to work with, and this first pipe will be rough, as the donor pipe was rough anyway.
    3. I took a few mins to mock up the bike for some motivation, just a general idea of where I'm headed. The MS tank won't really work but is what I had laying around.
    4. The RM airbox was kind of modern at the time, as it wasn't really a box but just a couple of sides bolted to the boot plate. They were making the fit difficult and would look too modern anyway, so I removed them. I will make some aluminum side covers, maybe that incorporate oval plates.

    Attached Files:

    #19
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  20. sruss67

    sruss67 Been here awhile Supporter

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    Looking good, nice work on figuring the bracket for the rear engine mount.
    #20