70cc kit jetting

Discussion in 'General Tuning' started by jakeh, Oct 14, 2011.

  1. jakeh

    jakeh Member

    Messages:
    53
    hi, i installed a 70cc kit on my yamaha neos yesterday.
    i was told to keep the same jet as it has before (81) for the first 10-15 miles to bet it in well....
    so far its going INCREDIBLE slugish... maxing out at around 35mph - i've ordered a size 90 (about 10% increase) jet but i feel like even with this it still wont go as fast as it did with the standard 50cc cylinder.

    did i do something wrong?
    or should this kind of speed be expected from bad jetting?
     
    DW28 likes this.
  2. jakeh

    jakeh Member

    Messages:
    53
    just took it out for a ride, i got to about 55mph down a slight hill, but then it cut out. my size 90 jet should've been here today but now i'll have to wait till monday to get it soreted.
     
  3. gary2011

    gary2011 New Member

    Messages:
    12
    u will need to ware the new 70 kit in, keep it to 30 for a few 100 mile or it might go bang
     
  4. jakeh

    jakeh Member

    Messages:
    53
    so i wont see any performance increases until its worn in?
     
  5. Jonnymarrw00t

    Jonnymarrw00t Moderator Staff Member

    Messages:
    3,243
    Rides:
    Piaggio Zip 05 plate
    1. Don't be a tit. You never do 50mph on a new kit! 30mph for 300 miles quater throttle!! or you're blowing more kits. Is it a 13ml carb ? If so standard jet would be 72, 10% would be like 79-85 range for exhaust, 5-10% for the 70's, What 70's is it ? What Roller weight you using ?
     
    Paul Smith likes this.
  6. jakeh

    jakeh Member

    Messages:
    53
    it was properly jetted when it had a 50cc cylinder, i bought the 70cc kit from a shop, it said something on it but no brand name.. i was told that its capacity is 72ccm.
    i'm not sure about the carb size but i guess 17.5ml

    roller weights are 3g which i think should be alight

    i've done about 100 miles so far so i'm still wearing it in
     
  7. TuningMatters

    TuningMatters New Member

    Messages:
    15
    Rides:
    Gilera Runner
    Every change in your engine components needs adjustment. You absolutely need to change the main jet. Instantly. Everything else is the biggest bull**** I've ever heard! Get a set of main jets. Stage6 has those nice and cheap ones. The cylinder will go fast at any time, it has nothing to do with wearing in.
    Also adjust your variomatic rollers. 3g seems to be too light. Also get an adjustment kit: Polini or stage6...
    You have removed all your engine restrictions, right?
    After 100 miles the cylinders i worn in. You should anyways take it off again and have a look at it. This downhill ride doesnt sound so good to me....
    Also make sure to use a cold sparkplug like a Bosch 3 or NGK 10!
     
  8. jakeh

    jakeh Member

    Messages:
    53
    adjustment kit..???

    and yeah its fully derestricted.
    the cylinder came with a spark plug, i believe it was an NGK iridium plug
     
  9. Jonnymarrw00t

    Jonnymarrw00t Moderator Staff Member

    Messages:
    3,243
    Rides:
    Piaggio Zip 05 plate
    Are you on crack ? It's a IRON KIT Yes you can run them in at 100miles but you shouldn't do it unless you build bikes and know what your doing! You should always do the 300 miles. Are you going to pay for his new kit if he goes pins it from 100 miles ? no. Do the 300 miles to be safe. You can buy a large kit full of rollers to see which set to use (Polini) but they are only to setup (Don't last as long) So you'd have to buy the right weight when you've got the right ones. Use the plug what came with the kit. But as said make sure you upjet.
     
    Paul Smith likes this.
  10. lshigham

    lshigham Member

    Messages:
    250
    This man talks sense. Running in a iron kit for 300mi at 30mph? Don't be daft.
     
  11. Jonnymarrw00t

    Jonnymarrw00t Moderator Staff Member

    Messages:
    3,243
    Rides:
    Piaggio Zip 05 plate
    So you're going against what it says in all the manuals ?
     
  12. lshigham

    lshigham Member

    Messages:
    250
    Yup. It's called arse covering.
     
  13. boweze_runner

    boweze_runner SR172 amazing but sold !!! dragster again soon :D

    Messages:
    57
    Rides:
    Italjet Dragster 180
    no its called being a fuking wanker but its you whos wasting the money not me....
     
  14. xplicit vehicle

    xplicit vehicle Member

    Messages:
    268
    Rides:
    PGO Big Max 50
    its not the speed u run the kit in but the revs
     
  15. jakeh

    jakeh Member

    Messages:
    53
    its pretty worn in now, but literly takes a mile to get to top speed, accel is shite, and top speed is less than before..

    and i feel that it was running better on the 81 jet :confused:
     
  16. jakeh

    jakeh Member

    Messages:
    53
    today it was going particularly slow, then after about 3/4 mile on full throttle it started loosing power then kinda backfired out the exhaust... i killed the engine immediately, and it started again fine, i'm just worried about riding it...

    what do??
     
  17. DW28

    DW28 New Member

    Messages:
    1
     

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