Derbi senda 50 running issues

Discussion in 'The Workshop' started by paul2k11, Nov 27, 2016.

  1. paul2k11

    paul2k11 Member

    Messages:
    51
    Hi my Derbi senda 50 is not running properly it's got a boggy set off so when vhanging gear it struggles to go right as the Rev needs to be there straight away can anyone help.
    It's a 50cc head standard carb with a 68 main jet
    It has a Doppler race exhaust
    It's got a metal mesh open air filter.
    Seems to be a jetting or air problem can anyone tell me what I need to try as I have had 2 new plugs which are going black too quick I would say
     

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  2. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    6,511
    put an airbox on it instead of the open filter, the airbox isnt restricted on those. 7hp from those with just a derestricted exhaust....
    try going up on the jet to about 72...
    im quite familiar with these bikes so just ask if you want to know anymore...
     
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  3. paul2k11

    paul2k11 Member

    Messages:
    51
    Hi thanks for your reply I got the bike with no air filter so was easier to get a open would it run better with a standard air filter? I just put a 70 jet in but need to go test it,and would I benefit from an upgraded carb or will that make no difference
     
  4. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    6,511
    try with the 70 jet and see how it is. we can go from there...
     
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  5. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    6,511
    i quite like the older sendas, the newer ones have piss poor quality, although the DRD pro is a great little bike...
    slow as hell when they are restricted, you can pull off in 5th gear....
     
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  6. paul2k11

    paul2k11 Member

    Messages:
    51
    Yeah I had the 2005 Derbi senda extreme it wasn't bad that had standard air box and did around 50/60mph on flats just had the exhaust derestricted and I didn't mess with the carb on that. I got this as a project i put through mot .I don't mind the slight bog on straights but when I'm going up sloped roads not too steep it's not going into 3rd as it slows too much when I let off throttle and then drops speed.
     
  7. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    could try the cowboy mod to the open air filter.

    slide a tube over the air filter so only half of it allows air in, its going to somewhat restrict that huge amount of air your sucking in. and give it a try up and down the road at your home ( do not ride on main streets incase you break down and put yourself or others at risk), its going to mimic a some what restricted airflow stock airbox , if you find this does the trick and the bike starts to pull nice through the gear range, you will need to grab a stock airbox to fit ( the above method is NOT a fix its just a test rig to see if a restriction will work )

    again do this some where safe and DO not rag the poor little thing if it seems to cure the lag/bogging, wait till you have a new box fitted.
     
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  8. paul2k11

    paul2k11 Member

    Messages:
    51
    Ok I have tried the 70 jet for 10-15 minutes and it was quite bad even on straights and I tried ajusting the air screw and no luck it was lacking power the 68 was better so would you recommend going lower. I tried a 56 before and that was no good.

    This cowboy thing what jet would you try with the cover up and what sort of tube could I use
     
  9. paul2k11

    paul2k11 Member

    Messages:
    51
    Hi again thanks for your tips I think the cure would be an origami airborne as I put some old filter sponge and poked into the bottom of my open air filter and it was still a little laggy /boggy but when through the gears perfect up hill and flat this was with the 70 jet which did not work without putting in any sponge in yesterday
     
  10. paul2k11

    paul2k11 Member

    Messages:
    51
    Origanal air box sorry
     
  11. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    sounds like you really need to get an original airbox buddy. standard cylinder and a derestrict pipe should not need a open air filter. your looking at more a high end bore kit wanting that sort of breathing into the motor.

    you may also want to look at the carb slide needle possible its been set incorrect to.

    Main jet = 3/4 throttle to wide open throttle
    carb slide needle - 1/4 throttle to 3/4 throttle
    idle/mixture screw = below 1/4 throttle

    Plug chop : use new plugs each time

    ride bike hard at wide open for 2-3 mins , then while at wide open turn off bike pull over and chop out.
    your not looking at the tip of the plug but the centre pole ceramic. down inside it should have a ring like stain you want this to be a milk chocolate brown stain ( running just right ) , if its white ( to lean ) if its black and wet ( to rich)

    to lean = move the throttle slide needle clip one ring down to richen mixture
    to rich = move the throttle slide needle clip one ring up to lean the mixture

    YOU MUST keep an eye on temps if your water cooled make sure she runs nice and cool , if temps start to peak up your running to lean and can seize motor / throw a ring / damage cylinder . if this happens its a whole new top end rebuild and possible bottom end strip down to make sure no metalics have gotten into the bottom end area and start mashing up the crank and bearings.
     
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  12. paul2k11

    paul2k11 Member

    Messages:
    51
    Yeah I messed with the needle as wasn't ticking over ,still doesn't properly I have to unscrew the adjusters on the throttle cable making me have not a lot of throttle left the idle screw can be put fully in and does not lift the slider to allow tickover that way??
    I will get a new plug today

     

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