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Thread: Anyone experienced with m40d carbs in Yamaha 25

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    Default Anyone experienced with m40d carbs in Yamaha 25

    I haven't done anything else. I wanted to do one mod at a time. After installing the carbs and matching the ports to carbs I lost about 500 rpm and 5 mph. Kinda wondering if it's because I need to open up the exhaust too. Anybody have any experience with this

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    2010 SRG 3 CYL CHAMPION 88workcar's Avatar
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    If you have not done anything else, that is not the place to start. Save them for later. It slowed down becuase you don't need it right now. I will help if you jet those down a little.
    Helping folks out around the globe.

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    I may just take them off for now until i can figure out what to do to my tuner. I know it can be shortened but not sure what else can be done. What size jets would you suggest.

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    2010 SRG 3 CYL CHAMPION 88workcar's Avatar
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    I will suggest do not touch the tuner. Most of what you hear and see for tuners is bull. Start with compression and 40hp reed cages with CCM reeds. Then porting and rework the compression again then a light flywheel. Then you can use the big carbs. Set up, props and weight removal is tremendous on smaller engines. Always remember that.
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    Xpress2830 Xpress2830's Avatar
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    Default Yamaha 25

    Good morning. If you have a 25 3 cylinder order a 30 tuner and leave it stock. My best results with the 40 carbs is with the .122 high speed jets. You will need a set of 40/50 reed cages. Order a set of Boyesen or CCMS reeds. Run boat bone stock record speed and RPM. Install 30 tuner and record #'s. Do reeds then carbs record each change you make. These carbs, tuner and reed cages wake these motors up. After this is done you should a significant increase in performance. These motors like all the timing you can give it. You can also start with your setup first. Jack plate prop weight distribution etc...Good luck..

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    What is the part number for the Tohatsu carbs?

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    Xpress2830 Xpress2830's Avatar
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    These carbs are hard to find. Look around on ebay etc... 40 carbs for MD40 or Nissan ND40. I will check also and let you know..

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    Xpress2830 Xpress2830's Avatar
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    I just read you previous post again. Have you put 40 carbs on this motor already?

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    I asked because I bought a Yamaha 30 that supposedly has "40hp carbs" but it wasn't a deciding factor in me purchasing it nor did the seller really know as he bought it a few years back that way and was just relaying info. I just want to check mine out soon and have a part number to compare to.

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