Donor bike options

Last weekend I laid fresh eyes on Kymco’s Xciting 500Ri and think that it could be a very viable contender as a Streetliner donor bike. Up to now, I’ve been leaning toward the Suzuki Burgman 400. The Burgy’s mileage is good, the motor is powerful, it’s a twin disk brake up front (meaning one disk/caliper set per wheel) and it’s a popular bike so the second-hand market should be pretty good. However, the Kymco has more than a few things going for it. The weight is the same, the mileage is similar, two front brakes, 12V accessory plug-in, good looking gauges, it’s got an extra 100cc of engine, but most interestingly an adjustable twin-shock rear suspension. The Xciting is also a bit less expensive, but still with Kymco’s proven Taiwanese build quality. In fact, I can’t help but feel a tad more confident in the Kymco, as they have so much more experience with scooters than Suzuki does.

But back to the suspension, which is what I’m most interested in. The rear suspension on the latest generation of the Burgy is a mono-shock underneath the frame. The Kymco uses the more traditional twin rear shock setup like I have on my Vespa GT. Previous Burgy models used a similar setup. What I’m wondering now is which will be better in my intended application? It’s easy to assume that the more sport bike style mono shock underneath the newest Burgman models is in fact an upgrade. But it could just as easily be a cost-saving measure. I’d probably have to ride both bikes to see if there was a difference in feel. But beyond the performance in the stock bike, how would that rear suspension behave plugged into a likely heavier vehicle with completely different geometry? A beefier shock will likely be needed. Will I be able to easily source one for the Burgman? The more traditional twin shock setup on the older Burgman models and the Xciting seem to offer greater flexibility. There’s already a nitrogen shock upgrade available from Kymco. But more than that, with the mount points so straightforward, I could conceivably use almost any shocks I want. In order to tune the suspension on the Streetliner, I’m going to need both dampening and pre-load adjustment. Although the current Burgman shock has seven levels of pre-load adjustment, it may not be the correct dampening. Fitting a different shock may involve some serious modifications. One of the guiding tenants of this project is to do as little engineering as possible, so the idea of having to re-engineer that more complex subframe to accept a different shock is not appealing. The sacrifice is that if I’ve got quite a bit of room above the engine for storage in the body of the vehicle. If I’ve got to have shock mount points above the motor, that could encroach on some of that space. But in the end, it’s not about maximizing cargo space, it’s about maximizing efficiency, comfort, safety, riding fun, and style.

8 thoughts on “Donor bike options”

  1. It’s entirely possible the stock Burg400 rear monoshock could handle your design – the 200lbs you’re adding over stock is balanced lower, more forward, and there’s a third wheel to distribute to. And the Suzuki vs Kymco designs handle unsprung weight differently, important since the big CVT scooters have their powertrains as part of the rear swingarm. I’m definitely not an expert on calculating unsprung mass, but the classic settup on the Kymco includes the weight of two shocks and force points more Up. The Suzuki uses a bell crank to separate the monoshock from unsprung, with the pivot point up and back a bit so force points lower and more forward. Will it matter? Man it’s hard to know until some brave fellow completes a big CVT scooter -based trike… Oh, I just saw one here but no detail, just small pics…

    1. You make a really good point. There’s only about 150 lbs difference between my goal weight and the stock weight of the Burgy. That’s no more than a middle-weight passenger. Being the premier touring scooter, riding 2-up has got to be assumed. I guess I’m just trying to hedge my bets on the greatest amount of adjustability. A quick Google search isn’t finding any shock upgrades for that unit, but that doesn’t mean they don’t exist. Either way, the Burgman is still the front runner as far as I’m concerned, but the Kymco has a lot going for it. When it comes time to make a purchase, it’ll likely come down to which I can have the cheapest.

  2. xactly, the best choice here is the one that moves you forward. The Burg is established enough that you have lots of options for actually getting it – new, used, salvage – and some options for tuning it – is a good reference. Not quite established enuf that there’s much of a market for ebay parts, so not much to recoup by parting out a nicer bike than you need. How much is in your budget for donor? Do you want something you can ride as is before cutting up?

    1. I don’t have a budget — at least in the sense that there is actual money set aside. What I do have is a design criteria to spend less than $10k on parts and materials. That hasn’t really been audited yet, so that $10k number may yet move. The guiding principle is to spend less than I’d spend for a really good motorcycle. The overall cost isn’t as much of a concern as much as how much I’d spend over a given amount of time. If the project costs me $10k and takes two years to build, that’s pretty reasonable in my estimation. Likewise, if it costs me $15k, takes me 3 years to build, but is completely brilliant, then who cares if it cost me $15k in the end? However, I’m not going to make any real material purchases until the whole thing is completely designed and priced out. It will also depend on if I could procure some sort of formal sponsorship. I haven’t even reached out for that sort of thing yet. Who knows? All that said though, if my cost audit shows that it’s going to cost something ridiculous like $40k, then I’ll probably just scrap the project.

      As for the donor itself, I already have a bike I love to ride (a Vespa GT200L) so I don’t feel a big need to have a rideable donor. I would like to ride a Burgman 400 at some point before I get a donor, just to get a sense for the power, but there’s not a whole lot of use in the donor being strictly rideable. That said, however, there are a lot of parts I want to harvest from the donor bike. Engine, electrics, brakes, gauges, and even precision parts of the frame (such as the engine pivot sub-frame). If the donor is wrecked up front so hard that the electrics are messed up and the front brakes are wrecked, then those end up being parts I have to get from other sources. Ideally, I’d like to have a complete, rideable bike, but what’s more likely is a salvaged Burgy, if not several.

  3. If you are debating the advantages of the different shock layouts, it might be worthwhile to consider the reason why most bike builders went from 2 shocks to 1 in the first place. See that section of this page.

    If both are coil overs it seems like it would be easy enough to get a different weight spring, but damping changes are another story. So it comes down to your priorities. Do you want lighter weight, less unsprung weight, and less shock fade, or a design where the shocks are probably easier to replace with a more tunable unit?


    1. Aaron, thanks for pointing that out. You’ve nailed it though, it’s about priorities. I’m not planning to track this vehicle or anything, so perhaps I’m overestimating my need for adjustability. The target weight for my vehicle is basically like carrying a passenger on the Burgy as is, so yeah, I could probably get where I need to go just on stiffer springs.

      Cal, I know just what you mean. I pass people on my Vespa GT doing 70 mph once in a while. The suspension is pretty good, so it’s not scary per say, but I can definitely tell that it’s not what the bike was designed to do. I often wonder if 250cc would be enough for this project, but what I keep coming back to is that very often a little bit bigger engine that doesn’t have to work as hard will usually outperform (in mpg) a smaller engine having to kill itself. Craig Vetter ran into this in his streamliner project (based on a Honda Helix 250). He’d have people ride with him on 650 motorcycles and get better gas mileage, even though he had the best aerodynamics of the group. My mpg target is 60 mpg, which from what I’ve been reading, the Burgy 400 already gets without any aerodynamic advantages of being streamlined. In a way it’s almost cheating, but I don’t care. This project is at its heart much more of an assembly job than a real optimization. I’m less interested in big numbers and completely uninterested in actually having to engineer anything.

  4. My first donor bike was an old Elite250 that I still ride – it was used as the donor for 600+lb Messerschmidt & Isetta replicas and owners reported good accelleration (top speed limited by those two designs). Driving that short wheelbase scoot @ 65 top speed is a little freaky, passing huge vehicles on the freeway is kinda surreal. But for the efficiency reasons you’ve talked about and because I live in a place w/ big hills and 80mph traffic, I went up to the Burg400. Got really lucky w/ a off-season ebay auction & for the same cost as the Elite250 ($1400) I almost doubled my power w/o losing any mpg (yay fuel injection). I commuted w/ the Burg400 for a year and am confident it’s a great choice for this kind of project. Expect to pay $1-to-3k for a salvage-to-used Burg400. If you get a rideable one let me know, I have an extra Thermoscud serving no purpose in my garage, makes the ride even more comfortable.

  5. I’ve been following Craig Vetter for some time too. I love what he’s doing, but personally think his goal is unrealistic. He wants to get 100mpg at 70mph into a 20mph headwind. That’s equivalent to getting 100mpg at 90mph on a calm day since rolling resistance doesn’t really scale with speed. It’s nice to have something to shoot for, but if your goal isn’t actually attainable it will turn into more of a hindrance than an inspiration.

    Nathaniel said:
    “My mpg target is 60 mpg, which from what I’ve been reading, the Burgy 400 already gets without any aerodynamic advantages of being streamlined. In a way it’s almost cheating, …”

    Here’s a way to make your goal a little more attention grabbing (you did say you were interested in sponsorship, right?) without making it unrealistic or unobtainable. Say you are shooting for 100mpg* (Canadian). With the measurement being in imerial gallons (1.200950 US gallons) that makes the US figure 83mpg. Since the Burgy already gets ~60mpg, its not unrealistic that some streamlining and perhaps a little taller gear (by simly changing the CVT roller weights) would get you over 80mpg at a constant “city commuter” speed of say 40mph.

    And 100mpg* has such a nice 3-digit ring to it.


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