Swapping CDI boxes

Discussion in 'The Garage' started by TheRadBaron, Dec 1, 2012.

  1. TheRadBaron

    TheRadBaron Been here awhile

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    I just drug home a beat up old Suzuki 4-wheeler. It's an '85 LT250EF, four stroke single. It's missing the CDI box and there aren't any available for a decent price on Ebay. I think this quad will run if I get a CDI for it, so I'm wondering how feasible it would be to swap a CDI from a different model onto it. I imaging that the variables are initial timing, total timing, and the advance curve. I don't know any of the specs and I don't imagine that they're be easy to find.
    I wouldn't think that the timing would vary much between different models and sizes of 4-stroke Suzuki quads, would it? Would it be doable to swap a CDI box from maybe a LT185? They're pretty similar other than their displacement.
    I know that there might not be anyone here that knows about these quads, specifically, but how about just general CDI swapping. Is it something that's commonly done, and is it usually sucessful?
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  2. stainlesscycle

    stainlesscycle Long timer

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    generally the cdi just needs power and a trigger. as long as you stay with ac or dc (depending on what the cdi needs/your stator output) and the trigger type is similar, you can pretty much make anything work. if you can figure out the pinout of the cdi you (in theory) could swap a $10 chinese cdi into it. look around for other models with similar timing...
    #2
  3. RickS

    RickS Been here awhile

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    I have seen a CDI on a klr 250 used on a klr600. It was plug and play. So it could work
    #3
  4. concours

    concours WFO for 41 years

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    Stator poops on those frequently as well. Be carefull, it (engine) may be all used up, like, as in an oil burner. Is the exhaust oily like a diesel? The mud caked the cylinder on those, no cooling, crazy overheating, worn rings/bore. $$$ Have fun! :1drink
    #4
  5. TheRadBaron

    TheRadBaron Been here awhile

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    I haven't looked at it too much, but there doesn't seem to be any oily residue in the exhaust and the compression seems good. I have no intention of restoring this thing or even making it nice. I just want a beater old quad that I can use like a tractor around the property and let the kids tear up.
    I have a really nice, original, '85 Honda ATC250ES Big Red 3-wheeler, but it's too nice and I can't bring myself to subject it to hard use. I don't think I'll have problems treating this hideous troll of a 4-wheeler like a tool.
    #5
  6. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

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    CDI's are either 4 or 5 wire, do you know which one yours is?
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  7. TheRadBaron

    TheRadBaron Been here awhile

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    There are 6 wires coming from the CDI, so probably 5-wire? Is the ground wire counted in the 4 or 5 wires?
    Can you tell me the purpose of the wires? I would imagine that there's a power wire, ground wire, trigger wire, a wire to the coil, what else?
    Sorry for all the questions. I'd like to learn more about CDIs in general. Thanks.
    #7
  8. stainlesscycle

    stainlesscycle Long timer

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    some cdi's have an additional direct wire to kill switch.
    #8
  9. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

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    OK, here is what appears to be the wiring for your quad:
    [​IMG]

    I'd just purchase a cheap CDI from one of the china bike companies and wire it in and see how it works. There are stock CDI boxes on ebay but they are $275 it appears, so I'd try something else first. You can probably find a newer engine for less than that.
    #9
  10. TheRadBaron

    TheRadBaron Been here awhile

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    Man, thanks for the picture! That's very righteous of you. The number of wires and wiring colors look like there are a few differences from the pictures of the units on Ebay, though. The ones pictured on Ebay have six wires, while your diagram only shows five. The ones that I'm looking at have a plug with a green wire and an orange wire that isn't shown on the diagram you posted. Also, your picture shows a blue wire serving as the trigger wire, but the Ebay units don't seem to have a blue wire. What model is the diagram that you posted for, specifically? The wiring harness on mine has been cut up a bit so it's hard to tell what went where.
    There's a guy who's parting out a similar quad on Ebay right now, so hopefully I can grab the CDI from him for cheap. I'm hesitant to put a Chinese CDI on anything. I really don't trust that stuff. Plus, I plan to use this 4-wheeler to ride up to a secluded cabin that I go visit from time to time and a breakdown while I was up there would be most inconvenient.
    Since it looks like you might have a manual for these 4-wheelers available, would you mind telling me the valve clearance specs while you're at it? Thanks again.
    #10
  11. Worroll

    Worroll Been here awhile

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    The main difference in CDI boxes is at what RPM it starts advancing the timing. That schematic has only one pickup, so it's got to be either mechanical timing advance, or done inside the CDI box entirely. I've only messed with the CDI on my 80 XT500. It had two pickups, one was initial timing and the other was advanced a few degrees. Inside the box was circuitry to determine what rpm to switch over. It was a few years ago, so I forgot the details. I actually built a CDI box that worked well for a few bucks worth of parts.
    In my initial testing of the bike, I bought it with the CDI dead, I actually wired the pickup and ignition coil to a GM HEI ignition module (automotive part) and a battery to make sure the thing ran. It did.
    #11
  12. tntmo

    tntmo Been here awhile

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    Find another Suzuki single cylinder model around the same year that has a bunch of CDI's for sale cheap, then find the wiring diagram for that model. If it looks like it will work, take a shot.

    I thought my DRZ250 CDI was bad, none on Ebay for cheap but lots of cheap DRZ400 CDI's. I compared the wiring diagrams and they were pretty close, so I borrowed my buddies DRZ400 CDI and it was plug and play and worked. Turned out my CDI wasn't bad, but it confirmed that you could use another model CDI.
    #12
  13. tntmo

    tntmo Been here awhile

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    Can you post a few pics of your CDI, including the wires/plugs? I have a DR350 CDI and if it looks similar we can maybe make something work here. I have the wiring diagram to compare with yours.
    #13
  14. stainlesscycle

    stainlesscycle Long timer

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    that diagram tells me that just about cdi from a 4 stroke will work. search xr70 cdi on that other site or "5 pin cdi" buy one for $20 - then google the pinout. match 'em up and go.

    actually all you really need is right here

    http://www.chinesescooterreference.com/electrical.htm
    #14
  15. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

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    Baron, I'm sending you a PM.
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  16. dentvet

    dentvet Long timer

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    Does the CDI care what kind of voltage is running in from the source coil and trigger? I ask because while many CDI are wired in a manner similar to that schematic shown earlier, many bikes have different specs regarding the stator coil windings.
    #16
  17. stainlesscycle

    stainlesscycle Long timer

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    99% of the time, the cdi just cares if it's ac or dc. .
    #17
  18. speedshop

    speedshop n00b

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    I'd say you'd be lucky to find a unit from a different bike that runs on another. The Japanese toyed with the idea of producing a 'one box fits all' in the early 1970's however they quickly realised their folly and set about coming up with as many devices as possible to prevent one unit working on another bike.

    True there are so many different boxes out there you may find one that runs on a different machine but its a shear fluke if it runs 100% OK.

    I've lost count how many CDi boxes I've taken apart over the years and there are as many different designs of 5, 6, 7, 8 or 11 wire Cdi units as there are bikes. There is no one set up that gives any advantage over another so its very clear this has been done to ensure you must have a specific box for that bike.

    Its different for the racing bikes never intended for the road market where what works best is king, you wont find all these silly different designs!
    #18
  19. Twin-shocker

    Twin-shocker Long timer

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    If you look on Ebay you will see 5 pin and 6 pin CDI units, intended for pit bikes. The 5 pin CDI is an AC unit, intended to work on bikes where the CDI is powered by an AC coil within the stator. The 6 pin type are for DC systems, where the CDI is powered from a battery.

    As long as you have the right one (AC or DC), and its wired correctly these units will work on almost all bikes. The value of the capacitor inside the unit, determines at what RPM the spark advances, and in many cases the pit bike units advance earlier, which tends to work well if you have things like higher compression or different cams.
    #19