Who's working on them

Discussion in 'Modifications' started by Karl81, Dec 8, 2018 at 2:04 AM.

  1. Karl81

    Karl81 New Member

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    I'm new to the 125. I have c70 1981 passports. I'm looking at getting the super cub 125 . I need to get more speed out of it. 55 mph is not going to get it. I need to have 60-65 Top and cruse 50-55 for a mile or two.
    I have changed a sprocket and beefed the little c70 up with big bore kit and it got me a little on top end. I just don't know about the fuel injected grom 125 they are putting on the 2019 cub. I know the new monkey hits 70mph but the cub is topping out @55mph. Has to be gears or injectors. I need just a little power Mr.Scott.
    Any tweaking on the grom motor to get another 5 or 6 mph?
     
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  3. OLD CT

    OLD CT Well-Known Member

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    I do not work on c70's BUT the CT70 stock exhaust is not designed to flow on power levels past 55. Do you have a better pipe yet? That is what I would get, and a stroker crank.
     
  4. Karl81

    Karl81 New Member

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    Trying to. Figure out how to tweak 5 or 10 more MPH more out of the new 2019 super cub. They put the 125grom motor on. It. top speed is 55 on it.
    I know the C70 and have gotten a few more mph out it by tweaking a few thinks. Any mods to the 125 moto? The new 125 monkey is doing 70 mph. should be able to get the super cub 125 to 60 mph by some tweaking. I know nothing about the grom 125 motor other than its built proof proven performer.
    I have a two mile stretch of road that is posted 55 but they run 65-70 on it. I need the bike to hit 60 so I don't get run over.
     
  5. racerx

    racerx Administrator
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    If you're looking for more top end from your `81 C70, add a stroker crank. A 52x51 108cc tune should give you an easy 60mph. You can go as big as 54x54...124cc which can easily deliver 65-70mph.

    OTOH, if you're talking about the new-gen, Innova-based, 125/EFI motored bikes...MSX125/Grom, Monkey and Super Cub, they're a world apart. Best info I've been able to find indicates that it's the same engine, across all of those models. The FI setup is as basic as it gets..."alpha-N", based on throttle position & rpm, plus O2-trim at part-throttle cruise. Changing the injector, on an otherwise stock engine is likely to do anything except increase horsepower. Might be possible to fatten-up the air:fuel ratio a bit, something best done with software, i.e. tweaking the fuel table(s) of the ECM. There's still little-to-nothing to be gained from such changes, unless something else is changed...like the cam, intake or/and exhaust which allows the engine to move more air, resulting in lean mixture. Some of the mph numbers owners have claimed are suspect, to put it politely. On the flat, there's enough hp for 60-ish top speed, depending upon wind direction, elevation and ambient air temp. 70mph...IDK...descending a steep grade, with a healthy tailwind, maybe. All things the same, 70mph requires ~70% more horsepower than 55mph. Somehow, I've never seen that kind of power increase from simple tuning tweaks, on a normally-aspirated engine. Honda overgeared these bikes, slightly. Going to a smaller countershaft sprocket will firm-up high speed pulling power but, since the speed sensor is in the engine, most of the "70mph" claims, from a sprocket change, are little more than speedometer input error. Any of these bikes should be able to deliver a rock-solid 50-55mph, with ~60 possible under most conditions. Anything beyond that is going to require substantial tuning revisions...more rpm, more displacement, or both.
     
  6. Deoodles

    Deoodles Active Member

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    The Grom I owned would do 55 on most roads but a hill could slow it down to 45ish so without a bore kit I wouldn’t expect more out of it
     
  7. Karl81

    Karl81 New Member

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    Thanks guys, I know I'm grabbing at straws. I just don't want to give up the cub to get 60 mph. Going over 50 on C70 gets a little shaky. I looked at the 125 lifan mod to the C70 but didn't want to mess with hydraulic stabilizer for the front end. With front sprocket and big bore I do 45-50. That's all I care for with the limits of its suspension on old school cubs. But the new dream cubs of the last 10-15 years have been 50-55 with the 110. The 125Fi should have a little more?
    I'm just stuck as I have my kid and favorite restaurant 4 miles way. I have to cross a causeway and bridge with 55mphh speed limit. Really need that 60mph. I ride the scooter all over town but can't. Cross the river. Same when I go to key west. My cousin lives off mile maker 9. Can't really make it across the causeway on stock island as it's a 55 mph. 4 lane.
    I guess that's just the scooter blues. 35 to 45mph Surface streets all day long but 55 mph connectors are just not worth it.
    2019 125 S-cub will do 55. I just need 5 more mph to not get run over.
     
  8. kirrbby

    kirrbby Well-Known Member

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    You could likely build yourself a nice 70mph CT70 for the same price you'd pay for the new 125cc scooter.
    Buy a good $1500 CT70. Build a good $1500 125cc motor. Add $500 worth of muffler and oil cooler...and ride.
     
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  9. fatcaaat

    fatcaaat Well-Known Member

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    There are bolt on motor kits for that new cub. You can bolt on to at least 190cc and regear and you will have 80-85mph power
     
  10. fatcaaat

    fatcaaat Well-Known Member

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    A new cub is like 4k and the bolt on kit is about 600. 4600 dollars to cross a bridge? Sounds like you need a different vehicle.
     
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  11. Karl81

    Karl81 New Member

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    LOL yea well I can ride anything but you meet the nicest people on a Honda Cub.
    Not many of the places I ride it are over 45mph posted speed limit. I only scooter ride on the beach, island, keys, intown... Just get to where you have to do 55mph posted road now and again. That's 60-65 traffic flow as no one does posted limits.
    Kiitts? What kits?
     

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