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XT 350 ... I wanna EFI it

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  • XT 350 ... I wanna EFI it

    So we are getting into riding season here in the Rocky Mountains. I got the bike out the other day and it gave me all sorts of fits with the carb. These are notorious for being a PITA due to the dual carb design.

    I'm thinking it is possible to EFI it and make it dead nuts reliable, but I cannot fing any info on EFI'ing a motorcycle. I know the new WR and XT 250's are EFI, but the whole intake is a different design.

    I know MS makes the MicroSquirt which is more than capable of being hidden on the bike and controlling 350 cc worth of engine. But how and what do I use as far as timing control etc?

    Bench race this with me guys. It needs to be economical and reliable ...

    Here's the vehicle in question:

    Click image for larger version

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    Whiskey for my men ... and beer for their horses!

  • #2

    Re: XT 350 ... I wanna EFI it

    I'd leave the timing side alone and just go with microsquirt controlling one or two injectors off some kind of cheaply welded together intake manifold. Probably be some serious trial and error on the tune without an O2, but I'm sure it's doable.
    Escaped on a technicality.

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    • #3

      Re: XT 350 ... I wanna EFI it

      I don't see why you couldn't put a standalone wideband on it for tuning? A 14# injector would probably be enough and you could "Y" or maybe use 2 but Y for the Throttle body? I'd think you could pick up a tach signal from the Ignition? The fuel pump / battery / alternator might be an issue, but I see it runs lights so it's already got one I'm guessing. If the alternator isn't up to it, there are some guys doing big alternators for dirt bikes -> super motard conversions. I'll see if I can remember / find them again.

      There's a lot of talk on here: http://www.msruns.com/viewforum.php?f=93.
      Flying south, with a flock of bird dogs.

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      • #4

        Re: XT 350 ... I wanna EFI it

        The stator/alternator is working perfectly so I don't think that'd be an issue.

        As far as sensors go, would I still need all of the typical ones that are used when efi ing a car? I know a TPS is a given, but being that this is an air cooled engine, does that change things?

        Thanks for the link Beags ....
        Whiskey for my men ... and beer for their horses!

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        • #5

          Re: XT 350 ... I wanna EFI it

          You can probably get away without a TPS since all I really use a TPS for is for an Accelerator Pump shot, and as far as I know motorcycle carb's don't have an accelerator pump because the high rpms and relatively low load.

          You'll want an air temp sensor for sure, and I'm sure there is a work around for the coolant temp, perhaps a oil temp? Or there is the mass air flow route too, find a suitably small MAF might solve some vacuum signal pulsing issues you may run into on the small engine.
          Escaped on a technicality.

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          • #6

            Re: XT 350 ... I wanna EFI it

            I was thinking oil temp as well. There are several areas on ther case that will accommodate a sensor.

            Any ideas on a small MAF? The local MC junkyard seems to think the used stuff is still worth big $$$. Could the MAF be considerably larger than the throttle body and still function properly?
            Whiskey for my men ... and beer for their horses!

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            • #7

              Re: XT 350 ... I wanna EFI it

              Any ideas on a small MAF?
              3-cylinder Geo?

              Could the MAF be considerably larger than the throttle body and still function properly?
              I would think it wouldn't have any problem. They work at idle on small'ish engines and that is relatively small volume movement. Definately no issue at WOT.
              Escaped on a technicality.

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              • #8

                Re: XT 350 ... I wanna EFI it

                what do the efi bikes use factory

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                • #9

                  Re: XT 350 ... I wanna EFI it

                  what do the efi bikes use factory
                  Most are Speed Density. Much easier to implement. MAP sensor, TPS and Air temp should get the job done with the MSI (I personally would use a MEFI since Im not that familiar with the megaS stuff) You should be able to pick up a throttlebody or two at the motorcycle junk yard for cheap (BMWs are pretty plentiful where I am) and the MAP sensor too. (I dont know how youd easily hook up a TPS to a slide carb). MAF requires a MAF sensor sized to the airflow requiremetns of your bike. A car sensor would "stream" and not give you the signal you need due to its very large size (even for a very small car).
                  BKB
                  www.FBthrottlebodies.com
                  Bruce K Bridges

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                  • #10

                    Re: XT 350 ... I wanna EFI it

                    I would ditch the MAF idea, speed density all the way - or maybe Alpha N, that's how many of todays EFI bikes run.

                    Microsquirt for sure. MEFI would require you to fit a "compatible trigger wheel" which is a pain in the butt on something that small.

                    Randal has a good idea about just controlling fuel, but remember you're going to need enough DC voltage to power a high pressure fuel pump.

                    Somewhere out there, the MS guys have a sticky on their forums about motorcycle parts that are usable and plentiful for small engines. The first thing I'd do is figure out if you can get a decent stator upgrade or ? to handle the 6-10 amps or so that you might need to run things.

                    With the MS you can do like the other air cooled guys, and either use Cylinder Head Temp (cheap sensor mounts to sparkplug), or oil temp (using a standard GM coolant temp sensor) as your "Engine Temperature" input. Air temp will be easy, just hang the GM sensor somewhere out of the way.

                    NExt thing to look at is, what type of trigger system is available for your ignition right now? how does the factory ignition work, is it locked timing or computer controlled advance with RPM? Knowing those details would give me more ammo to help move the project forward.
                    www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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                    • #11

                      Re: XT 350 ... I wanna EFI it

                      And then... when it's just about tuned... get one of these and start all over! A turbo... hmmm, is that an approved spark arrestor?

                      Click image for larger version

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                      Flying south, with a flock of bird dogs.

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                      • #12

                        Re: XT 350 ... I wanna EFI it

                        You know Beags ... I have really been thinking about a turbo. The only one I ever found was a company called Blouch(?), but the cost kept me from actually doing it. IIRC,. the small one that would work on that size Engine would have been around $1100 .... American! That MBE seems more reasonably priced at $350 ..... Hmmmmm
                        Whiskey for my men ... and beer for their horses!

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