Scoot won't climb hills

Discussion in 'Battle Scooters' started by ChipsonFriday, Dec 21, 2013.

  1. Cortez

    Cortez BAZINGA!

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    I've sold and ridden over 100 Speedfights in 2 years+ that I worked in a
    dealership and saw them come and go later with different mods and
    user experiences.

    One that "stuck" with me for a while was when a guy put in a rather
    cheap 68cc kit (I have no idea which manufacturer, but it was not the
    polini/malossi bunch) on a completely stock scooter.

    That bike was virtually as fast as the Speedfight 100 (air cooled 9hp,
    2 stroke), and still quiet as stock. Funny thing is, the cylinder/piston
    kit was cheaper then the stock 50cc replacement.

    He did over 12k miles on it before I quit that job, so it was reliable too.

    That thing would spin the rear wheel (bare in mind that this scooter is
    only 200lbs or so) at full throttle from stand still. Ridden at a normal
    pace the fuel consumption also wasn't any worse then stock.

    I'd never use a sports variator or exhaust on mine. Mine DID come with
    the Leovince ZX pipe, but I took it off. The scooter had same MPG figures
    as my 650cc Kawasaki with it which makes no sense.

    Anyways, SF and SF2 were rather specific scooters and a lot of knowledge
    of different scooters doesn't apply here. The stock CVT and carb are good
    enough even with a tuned engine.

    I just wish Dr Pulley sliders were available back then so I could have experimented
    with those too as I have in my Downtown 300 (and it did wonders).

    Long story short, to the original poster, I'd get just slightly lighter rollers
    and take it from there.

    I hope there weren't many differences between different markets
    regarding CVT parts. I'm not sure if the stock weights on mine were
    9gr, that sounds a bit high.

    I'm sure 5.5gr would blow the engine up in a few hours.
    #61
  2. bikeridermark

    bikeridermark Long timer

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    I think the smaller the engine, the smaller amount in roller weight change is needed. Best to think of it in a % change.
    Clutch springs are more of an engine powerband thing. Raise the powerband, raise the strength of the cultch springs to raise the take-off rpms.
    #62
  3. k-moe

    k-moe Long timer

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    Only at the bottom end of the powerband, and it depends on whether you want to have control at parking lot speeds, or are only interested in hard acceleration.
    #63
  4. Motovista

    Motovista Parts is Parts

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    If someone put a pipe on, they may have gone to a lighter roller too. That's a pretty common swap.
    It miight help to know if this is an lc or ac speedfighter the OP is trying to sort out. Either way, he's not trying to make a reliable daily driver, he's trying to tune it to go up a hill that it's not going up now with the present set up, and enter a drag race, and ride it to work. 5.5 is not a very light roller in the world of 50cc scooters, and at the end of the day, the OP can put them in, try to go up the hill, and then ride it around a bit. And if he puts in heavier weights and it works better, that's okay with me too.
    #64
  5. Motovista

    Motovista Parts is Parts

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    What anybody who knows scooters knows iss that clapped out Ditech pos you are trying to unload on someone is a bad experience waiting to happen. Apparently you've figured that out too, and are trying to make it someone else's problem before it goes south. That's the smartest thing I've seen you do on this forum, a much better use of your time than making nonsensical remarks after I post a comment. Cortez didn't indicate 9 grams was stock.
    Finding a link to something on the internet is not the way to prove something works or doesn't.
    The owner of the SF is a motorcyclist. He can try lighter weights, and if the motor is screaming, remove them. It's that simple. What he has in there now isn't working, and 5 or 5.5 grams are not crazy light for a 50cc 2T.
    #65
  6. Chillis

    Chillis Land Barge Pilot

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    I can't think of what my Ditech bike has to do with this thread. Great to see you contributing more unfounded clutter based on ass'umption.

    Keep going. We need more Ivy league posts.
    #66
  7. blugg1

    blugg1 Been here awhile

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    I noticed these "low" weights on rollers some of you have mentioned. Made me a bit nervous as I have 16 gram 20x15 Dr. Pulley sliders on my SYM HD 200 EVO and they seem to work just fine. Peppy acceleration and a top speed near 80mph. But then it's a 200cc scooter. I suspect that makes a difference.
    #67
  8. Chillis

    Chillis Land Barge Pilot

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    All depends on variator design and HP.

    My stock variator in the SR50 came with 5.3g weights. The Malossi Multivar 2000 came with 7.2g but 6.75g are optimal for most folks who are heavier.

    One size does not fit all engines.

    My RV250 comes with 22g rollers which are as heavy as rollers for bikes that are almost double its cc.

    A Burgman 400 uses 19g weights. Yet again proving variator design and not engine size are the determining factor behind correct weight usage.
    #68
  9. Motovista

    Motovista Parts is Parts

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    You suspect right. Here is an excellent table about the differences roller weights can make in Scooters ; http://fc.greensboroday.org/~epaynter/brcvt
    #69
  10. Dan V.

    Dan V. Been here awhile

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    Ouch. A lot of over-analysis here, and some over-reaching. Fact is - CVT tuning is a balancing act. Change one thing, and it affects the operation in one way or another.

    Facts = OP is a hefty guy. Mechanically, the scoot can't climb a certain hill. To climb a hill, the CVT must be in "low gear". To lower the "gear ratio" the belt must ride higher (larger diameter) at the torque driver pulley when the load of the hill slows the scoot down. The torque spring controls the effective diameter of the of the pulley. If the effective diameter does not increase under that load then the torque spring is too weak, or the variator weights are too heavy. To remedy, you need a stronger torque spring or lighter vario weights.

    Thus, the original suggestion to lighten the roller weight would be the first place to try and remedy this situation - as the OP mentioned he had replaced the Torque Spring. If the Torque Spring had not been replaced, that would have been prudent, as they weaken with age. The key to tuning at this point is finding the right roller weights.

    Still no go? The Torque Driver itself may be in need of greasing or replacement. Aftermarket TD's usually have several different ramp angles that alter the way the TD "shifts". This can make a noticeable difference in the performance.

    The belt must be the proper length - even slightly off, longer or shorter, can affect performance markedly.

    Increasing power will greatly help in getting up hills. Easiest way is with a de-restricted performance pipe. Piping up raises the powerband to higher rpm's. You must use lighter rollers, and stronger clutch shoe springs with a pipe as you have to get the motor revved faster to get into the powerband. If this balancing act isn't done right the scoot could run worse.

    You must remember that with a twist and go scooter you have to tune to keep the motor in its powerband. The engine rpm's will be fairly steady as the CVT ratios control the scooter speed.

    I'm think most of this has been mentioned in this lengthy thread. Hopefully, I have clarified the CVT operation some. Tuning these wee beasties to get everything balanced and working well can be frustrating, but it is worth it when you have a sweet running machine :clap
    #70
  11. Cortez

    Cortez BAZINGA!

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    Dan said it.
    That's the bottom line.

    Also, with a 5hp engine, that scoot can run up vertical walls, it just needs
    lighter rollers, and very little can do a lot.
    #71
  12. ChipsonFriday

    ChipsonFriday Adventurer

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    Thanks for the input guys.

    Dan, Your post nicely summarises my conclusions after reading through all of your posts. I suspected I needed to make/force the ratio into a low gear to get me up the hill. As I said early on, if I have a bit of speed when I enter the hill I can get to the top. However starting from a standstill I have no hope of even moving forward.
    It's a bit like peddling a bicycle up a hill in a high gear - the same principle. Put the bicycle in top gear and try to peddle up a hill, it's not going to happen.

    To clarify a couple of points then:

    The SF is air cooled.
    I have a new stock belt and variator with 8g weights
    The torque spring is new (1000RPM). I have two other new torque springs which came in the set, a 1500 one and a 2000 one. (I haven't tried these)
    The clutch springs are Mallosi Red.

    So I agree that I need to keep the variator plates apart and the torque spring end closed to produce my low gear ratio at the same time as producing some power from the engine.

    My only frustration is not knowing when the engine is in that powerband. No rev counter on the scoot.

    The weather is set to improve and I have nearly finished the work I was doing on my other bike so I can soon restart the experimenting on the scoot.

    Thanks again for the support.

    Chips
    #72
  13. Cortez

    Cortez BAZINGA!

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    Oh, that's a bummer, that one is about 20% down on power compared
    to the LC version, uses the engine from the Vivacity/TKR/Trekker so
    those parts fit.

    Good news is, it has a wider power band with torque kicking in at lower
    revs.

    The LC has around 1000 revs between max torque and max power.

    I stick to my first suggestion, especially considering you already have a
    stronger spring.. 10% lighter rollers (or about 1gr).
    #73
  14. ChipsonFriday

    ChipsonFriday Adventurer

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    Thanks Cortez. I've just fitted 6.5g and now waiting for the weather to improve to test it.

    I'm not generally a fair weather rider but I'm not getting fully kitted up for a quick run out.

    Chips
    #74
  15. Cortez

    Cortez BAZINGA!

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    Good luck! :freaky
    #75
  16. Chillis

    Chillis Land Barge Pilot

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    On my SR50 with variator designed for heavier weights, a change of decrease of .5g will raise the rpm by 600 to 700 rpm. Since you don't have a tach, the way you know you have gone too light is your bike will be revving like mad without going anywhere. From 8g to 6.5 is a huge difference. Don't run it long if it operates as described above.
    #76
  17. Dan V.

    Dan V. Been here awhile

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    Chips - the Malossi red clutch springs are their stiffest. I would estimate that they hit at 8 - 8.5k rpms, if not higher (depends on the weight of the clutch shoes) You would use the red ones in a highly sport tuned or drag scoot. Using a stock exhaust with those springs probably gets the the engine rpm's past the power band before the clutch engages - which generally would cause the scoot to perform poorly. High clutch engagement rpms make the scoot hard to handle on the street, particularly when turning from a stop. I think you would like living with the yellow better, which would drop the engagement by 1000 rpms or so.

    Your recent post states you have 8gm rollers. I might suggest the Malossi yellow Torque Spring may work better with them as it would keep the faces closed longer.

    If you have to get into the clutch/torque driver I would suggest disassembling the unit if you can get the sleeve off. Check for smooth operation of the drive ramps. Any wear in the ramps can cause big problems. Luckily, some TD's have more than one set of ramps. Clean up and regrease the ramps.

    Trying to tune w/o a tach is damn near impossible, and adds to the frustration. I use Koso digital units that are reasonably priced. If you see the rpms drop a lot after take-off you know the CVT is not set up well.

    Good luck - you are on the right path. BTW, pedparts.co.uk has a great blog that has dyno charts for different pipes. Def worth a look.
    #77
  18. bandito2

    bandito2 Been here awhile

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    I pretty much addressed points in my post (#62) about forcing the lower ratio, but didn't think to add about the belt length.. Good call Dan V.

    Low cost way to check RPM is with an inexpensive little gadget called Tiny Tach.
    http://www.tinytach.com/

    Available from various places. Here's just one place.
    http://www.amazon.com/s/?ie=UTF8&ke...vptwo=&hvqmt=e&hvdev=c&ref=pd_sl_1jrgglvnzb_e

    Good luck with your scoot.
    #78
  19. JerryH

    JerryH Banned

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    I seriously doubt that a 50cc CVT scooter will ever climb a steep hill with a 240 pound rider. And the reason is gearing. 2 hp will easily pull the scooter and a 240 pound rider up a step hill, IF the gearing is low enough. I have never seen a 50cc CVT scooter with a low enough gear ratio, even if you could keep it in the lowest gear ratio it has.

    Put a tachometer on this scooter, and ride it full throttle on a level flat road. Note the rpms. To climb a steep hill with that much weight on it, the engine is going to need to be spinning about the same rpms as it was at full throttle on a level road. With a manual transmission you can do that. But not with a CVT.

    If you find a way to do it, I'd sure like to know what it is.
    #79
  20. blugg1

    blugg1 Been here awhile

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    Me, too.
    #80