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Custom chopper/bobber questions.

Discussion in 'Modifications and Projects' started by boingk, Sep 17, 2008.

  1. Hi there. I'm up for buying my first bike over the next few months and after biding my time and looking around over this final year at uni, I though making my own over the summer would be a bit of a hoot. I've got mates who are willing to teach me welding and so on, and some space/tools to get things up and running without too much hassle. What I'm mainly after is advice.

    I'm after something which is low, lean and relatively nimble. Also, I think a hard-tail would be nice as I like the relative simplicity of them as well as the look. I'm not a fan of huge rake angles so rule big forks out. Basically I'm looking to use this bike as a long-distance and recreational item; it won't be my only mode of transport.

    At this point in time ideas and plans are pretty wide-open, so any suggestions of info (or material!) resources would be greatly appreciated.

    Cheers - boingk
  2. Your first port of call should be your local RTA to find out what they'll licence and whether it'll be an Individually Constructed Vehicle (which it will be if it's got a one-off frame).

    Next is to go to Dotars website to download all the ADRs relevant to an L-Group vehicle.

    Either Dotars or your local RTA's website will also provide you with a download of the National Code of Practice for Light Vehicles, which gives a lot of useful general information about the legalities of constructing a one off vehicle. It does have a motorcycle section although it's rather sketchy. There's a National Code of Practice on trikes too, which probably contains more of relevance to bikes.

    You'll probably have to engage the services of a Consulting Engineer who will both certify that your bike complies with all relevant ADRs and also is qualified to confirm that, for example, your one-off frame design is adequate for the task and that your chosen forks aren't going to collapse under the stresses imposed by those huge twin discs.

    Having done all that, you can start sketching out your design. It's a good job you don't like over long forks because there are clauses in the ADRs that specifically prohibit them, at least with big rakes. No, many of the "choppers" advertised in places like Just Bikes cannot be legally registered in Australia, which would be a bit disappointing to find out after you handed over the cash.

    Think carefully about whether you really want a hardtail on a bike for distance work. If you did go for it, I'd recommend a sprung saddle or at least a decent thickness of foam.

    Having been involved in building a couple of budget chops in the UK (where the legal/engineering process was much easier), I'd offer the following main points:-

    Start with a complete donor bike. A stat write off due to frame damage would be cheapest. Late model big naked would be preferable. Bandit engines are superb muscle chop power units. Engine, electrics, drive train, back wheel/brake can then all be sourced from one place, avoiding compatibility headaches.

    Modern dirt bike forks are great for chops. Get the whole front end, wheel to steering stem and set the rake to give you reasonable trail. That then determines headstock position. Frame buildng then becomes a question of connecting headstock to rear wheel spindle (or swinging arm spindle if you've gone for suspension) as rigidly as possible whilst leaving a hole in the middle for the engine.

    Build a frame jig. There is no other way to ensure everything lines up. Steel is cheap.

    Get to know someone with a lathe. You will lose count of how many little round thingies you will need. Alternatively, spend your paint and chrome budget on a small one and learn to use it.

    If you're intending to build an entire bike over the summer, be prepared to forget having a social life or any money. This is neither a small nor cheap undertaking. Even a basic chop, from scratch, by a first time builder, is likely to take more than three months. Get the legal stuff sorted now though, as that can end up being the biggest delay come completion.

    Building your own bike is a tremendous buzz when you first ride it, mainly because it is quite a difficult thing to do.

    Good luck.
  3. My advice is to buy a registered bike in good condition from the 70's, 80's that you like the look of and are happy to ride re size, power and budget then bob that. I have a few different pics of Bobbers made from small singles/twins up to 4's. It can be done quite cheaply.

    The Yamaha XS650 and TX650 have a huge following but are hard to get now (I am on the lookout if anyone has one!) and I have seen great jobs of GS750 Suzukis and the old Kawasaki Z's and Honda CB750 can look great but getting expensive! Of course late 60's and 70's Triumph and BSA probably make the ultimate bobber unless you can stretch the budget to a Harley Knucklehead or Panhead. If I was going to use a newer bike the late 90's Kawasaki W650 is a superb base (hard to find) and the current Triumph Bonneville twin is just begging for some treatment!

    Some of the old thumper trail bikes make great Bobber projects, I have thought of using a Yamaha XT550 as the basis of one and have seen XT''s done. The old SR road version is even simpler! You don't always have to hardtail either, just use small shocks dropped down to retain some comfort.

    Here are some pics for inspiration taken at Taren Point in Sydney on Father's Day. IMHO a bobber looks a lot better than a chopper and they are a pretty hot item at the moment. A lot are turning up at Car and Hotrod shows. You could do anything from this (cheap small Honda or Yamaha)
    To this (Triumph)
    To the ultimate (Harley Panhead)
  4. Thanks for the reply, guys! Don't think I could have got a better pair of responses.

    PatB - Cheers for the info, had a bit all ready but wasn't sure what else I'd need to get in order. At this stage I'm planning to buy a whole bike and modify, so an engineering cert and adherence to all the then-current ADRs should see me through it from what I can gather now, not as bad as I thought.

    I'm weighing up between plunger suspension and hardtail...I'd like to go hardtail, but can always convert to a plunger rear suspension anyway which is my prefered plan 'B'. I've got mates who work at an engineering firm that are willing to give me some pointers on regulations and technical skills as well as loan some equipment to use. Provided I cover the consumables like welding rods and beer when we're at it, of course.

    Dave! Exactly what I'm thinking of doing, midsize multi-cylinder or large single jap bike type job. Something like what I found below:


    And if I get sick of that in a few years, then this:


    Thanks again guys, good stuff - boingk
  5. That Honda actually looks excellent except for the Comstar wheels! The Sportster tank and single seat are perfect and note that it retains some rear suspension. Hardtails get kind of annoying after some miles!
  6. Hey dave the two black bikes in your pic are mine and a mates. The TW200 i did last year and the other one beleive it or not is a current mod CB250. I have just bought a another( tonight bout 2 hours ago ) CB250 to mod then prob sell my TW200. If your looking for good donor bikes take a trip to your local dealer and have a look at bikes and frame dimensions it can make the build process much smoother if you have a good base to start with. Pil
  7. Hey dave the two black bikes in your pic are mine and a mates. The TW200 i did last year and the other one beleive it or not is a current mod CB250. I have just bought a another( tonight bout 2 hours ago ) CB250 to mod then prob sell my TW200. If your looking for good donor bikes take a trip to your local dealer and have a look at bikes and frame dimensions it can make the build process much smoother if you have a good base to start with. Pil
  8. Hi Pil, I was standing just near you when you rode out! I had only a quick look at your bikes but was impressed as they looked like cheap fun and we have had a few over on the Ozrodders forum wanting to build a basic bobber similar to yours! I nearly bought a TW200 a few days ago but missed out :cry: . I am on the lookout for an XT550 at present, plan to lower the rear but have it look hardtail and have a couple of Harley tanks spare. Are those Supertrapp mufflers on that Honda?
  9. If you're looking at modifying rather than building from scratch, like Dave said there are lots of good candidates.

    Back in the UK, the universal budget custom was a Suzuki GS550/750/1000 with a 50 mm stretch in the swinging arm (as well as lengthening the bike it cants the shocks over so the rear sits lower), dropped seat rails and a set of drag bars. Starting with a rounded tank model, even the stock tank looked OK, although advanced students would replace the stock triple top tubes of the frame with a single tube (often a length of scafhold pole :shock: ) to allow fitment of an aftermarket mustang or sportster tank. Skimpy front mudgaurd, trailer rear guard, topped with a cheapo, aftermarket enduro tail light, sidepanels made up from stainless or ally sheet, small Bates headlamp, speedo removed from instrument cluster, universal banana seat.

    Obviously, other UJMs would also be amenable to this treatment, but the GS range seemed by far the most popular subject. Given careful attention to detail and some finesse in construction some of these bikes looked fantastic and remained practical roadsters.

    Incidentally, on the subject of tanks, at one stage the Honda CX500 Custom unit was very popular. Reasonable facsimilie of a sportster, with a factory vacuum tap and mountings that could be made to fit an awful lot of Jap frames without too much hacking about. Dunno where you'd find one now that wasn't rusty or dented to buggery though.
  10. this is a suzuki gs something isn't it?

  11. Nah, that's an SOHC Honda. An early 750 at a guess, as it appears to be dry sumped with a separate oil tank.

    But yes, that's a good example of the sort of thing I was talking about, although the swinging arm and seat rails appear stock.
  12. Two thoughts.

    If you are considering long distance riding then re-consider the hard tail. and also consider just taking the frame and taking it to a professional welder.
  13. ahh, you're right, i remember where i got the photo from now.
    i try to make up for lack of knowledge with enthusiasm...

    anyway, a fair few people seem to be getting good looking bikes by sliding the front forks in the clamps an inch or two, and lowering the back by the same amount + styling and seating mods.
    though it sounds like you want to build something, rather then spend time hunting for parts on the internet
  14. PatB - Yeah I dont mind the CX500 tanks, was actually looking at buying a junker to do up a while ago. As for capacity and bikes, I'll be on my P plates for the next year so figured I would get something legal LAMS-wise. Theres a awful lot of candidates out there, for sure! If I get stuck for 'the perfect (whatever)', I'll just do the usual and cruise the junkyards and wreckers around the place :)

    ibast - am definitely having a good hard think on the hard tail, its my main decision and starting point once I get a bike to start working on. At the moment I'm thinking of doing for the hell of it, and then converting to plunger suspension if I don't like it. As for the professional welder...I've thought about that and its out due to expenses. Also, I'd rather do it myself; with equipment around and mates in the game I don't see why I couldn't. Obviously, I wouldn't start my welding on the bike, I'd stuff around with some scrap first until I got the hang of it. No way I'm going to butcher a bike with my current welding skills, even under the guide of experienced mates.

    pil - best looking CB250 I've ever seen, hands down. Good work!

    - boingk
  15. You have a multitude of choices that would all still be LAMS (and P) approved. I saw a bobbed BMW R50 for sale on Sunday! (NSW rego) that would be legal and the CX500 and various others should also be. There are always plenty of suitable bikes on Ebay and way better to get a going and regod bike than one from a junkyard. Personally I think wire wheels look better on this style of bike and I am no fan of the early Honda comstars though some of the 'mags' can look okay. You can often just use shorter shocks to drop the rear of the bike without having to do extensive frame or swingarm mods and as others have said any subsequent welding should be of the highest standard and appropriately engineered.
  16. Just to make the point clear the cb250 wasnt built by me but by a mate with a ton more skill than I have. If anyone lives on the northern beaches( brookvale) you can take a look at his work. He will be building more bikes for sale soon just gotta find good low kms bikes to chop. His company name is EVOLUTION MOTORSPORT . You think the photo of the bike looks good you should see and hear that thing in the flesh its a whole other ballpark. Pil