aprillia rs 28mm carb on a 172

Discussion in 'Maxiscooter Tuning' started by rideorcollide, Dec 15, 2009.

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  1. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    I won a 28mm carb on ebay today.. 25 quid, but its off an rs.

    i know i need to drill it out for a vacuum and run premix, but i was wondering if it will run really shit.. and if ill need to change everything in it to get it running good..

    could anyone tell me out of these thing, which ones i will and wont have to change:

    main jet (obviously change this)
    pilot jet?
    atomizer jet?
    needle?
    slide?

    thank in advance for any help :mrgreen:
     
    rideorcollide, Dec 15, 2009
    #1
  2. seanwhite06

    seanwhite06 New Member

    Messages:
    358
    Rides:
    runner 172, zx6r
    using the rs carb also myself and the main thing was changing the needle.
    idle jet seems to be alright.
    running a main of 109 and plug seems a nice colour.
    specs a 172, pm59, 28mm etc etc.

    definetely harder to setup right compared to a 25mm dell but not rocket science just follow the quides etc. Def worth the power gains though! :grin:

    also dont forget to check the slide opens all the way as my standard throttle assembly would only open the carb about 3/4 of the way!
     
    seanwhite06, Dec 15, 2009
    #2
  3. 172runn3r

    172runn3r New Member

    Messages:
    72
    I was using 1 off a nsr 125 same carb

    55 idle jet, 117 main jet, needle 2nd from top and ran fine.
     
    172runn3r, Dec 15, 2009
    #3
  4. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    erm, the rs carbs HAVE an oil feed....only need to drill for a vac... dont HAVE to run premix atall. if it doesent have an oil feed its not an rs carb.
     
    MiNoR cOnFuSiOn, Dec 30, 2009
    #4
  5. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    i wanted to run premix anyway..

    would i be able to take out the oil nipple and make the hole a little bigger so i can stick a vacuum nipple on there? or does it have to be the same place as it is on a malossi carb?

    i've just been test riding it and it only runs with the choke on... when its off the engine will bog and die when i open the throttle quickly. (rides about 10m before this starts happening)

    i've got the vac connected to the casings next to reedblock atm with a t-piece.

    and im running a 110 main jet.
     
    rideorcollide, Dec 30, 2009
    #5
  6. breamy

    breamy New Member

    Messages:
    532
    Rides:
    Typh 172
    needs upjetting
     
    breamy, Dec 30, 2009
    #6
  7. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    ive gone from a 102 to a 110 already.. u reckon i really need to go higher? ive got up to 120...
     
    rideorcollide, Dec 30, 2009
    #7
  8. nrgandy

    nrgandy New Member

    Messages:
    2,180
    surely if it bogs it needs less fuel it took me ages to get it to run right on the last 125 typh i had im sure minor said the best way is to use a diff needle im not sure if one out of a 25mm would work or not.
    just read up on the carb guide and have a play till you get it right way worth taking your time to get it right
     
    nrgandy, Dec 30, 2009
    #8
  9. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    dunno, im gonna buy some needles soon though when i find out what the letters mean lol.

    what does the choke actually do?? more air or petrol?? because that would help me work out if need to upjet or downjet coz it runs fine with the choke on
     
    rideorcollide, Dec 30, 2009
    #9
  10. adz452

    adz452 Member

    Messages:
    710
    Rides:
    Vespa T5
    the choke richens the mixture
     
    adz452, Dec 30, 2009
    #10
  11. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    ok, the problem you have is a mix of a couple things... first BLOCK THE OIL NIPPLE UP. its past the slide and draw's air straight in (where the carb cant add fuel) so its lean as fuck, hence you need the choke on.

    the choke works by BYPASSING the slide (see it open from the front down a hole) air go's through this hole (easier than through the small hole in the slide when the throttle is closed) then the air hits a jet (the choke jet) this then feed's the set ammount as per the jet of fuel to the air rushing past, this is dumped back into the carb just past the slide (obviously) and the engine runs of THAT mix.

    the needle is another big blunder wiht these carbs, as andy said there too thick unless you run them high (like second from bottom) with a silly big jet and then your just making heat and no power just to rev. needs a thin needle (73 i belive it is, dont quote me) at the top, at most second from top wiht a smaller pilot jet (correct the mix wiht this so the perfect screw setting is around 1 and a half turns out... dont just turn the screw all the way in/out and hope) and yes start big on the jet, bigger carbs need roller ajustment (could be up or down, depends how its acting, only you know that) but ye, this should keep you going
     
    MiNoR cOnFuSiOn, Dec 30, 2009
    #11
  12. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    ahh kl that helps a bit,
    i blocked off the oil feed earlier..

    what about the vacuum though??

    can i leave it connected to the casing with the 't' piece, or should i drill out the oil hole and put a bigger nipple in there, or just do it on the top where they put them on the mallossi/polini carbs
     
    rideorcollide, Dec 30, 2009
    #12
  13. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    never run a tap off the pump vac (the one under the reedblock) wihtout a one way valve (basicly dont do it) that pipe sucks and blows as the piston go's up and down, the one in the carb is the other side of the reedblock so ONLY sucks.. running the tap off the pump with a t peice will just open and close the fuel tap with EVERY SINGLE revoloution of the engine (soon kill the fuel tap) and they CAN suck fuel through them, so no, drill your carb, check your fuel tap/float are working and sort the needle (lift it right up and throw a big jet in untill you can get yourself a thinner needle)

    you drill it the same as any other dell carb, the oil fitting on them needs blocking up WELL and forgetting about.
     
    MiNoR cOnFuSiOn, Dec 30, 2009
    #13
  14. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    ok so ill drill it out on the top, needle clip on the bottom notch, idle mix nearly all the way in and then mess about with the jets..

    kool, should be on road pretty soon now.. just got a garage to work in aswell so no more cold hands and getting dark at 4 :cheers:
     
    rideorcollide, Dec 30, 2009
    #14
  15. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    no, the screw will sit right out usually as the pilot jet is too big (the small one) some have stupidly small ones in for some reason (fuck knows) cant remember what sort of size your after, havent done one in nearly a year now (fuckinell) but ye, ajust the idle mix till the engines happy (well, least unhappy really) will usually need a diff pilot jet tho. but ye, should get you going for now... if not you need a needle/possibly a slide, a set of pilots and a few hours. OH and a few fresh plugs for when they burn out LOL
     
    MiNoR cOnFuSiOn, Dec 30, 2009
    #15
  16. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    ahh slide was the other thing i knew i had heard someone say you need to change that, will do pilots when i get it dyno'd.

    im suprised the plug thats in it is still alive tbh.. im running it at 35ml to a litre, i swear thats quite alot
     
    rideorcollide, Dec 30, 2009
    #16
  17. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    if its good oil it will burn off, some cheaper oils are good for this, altho even wiht a shitty oil you dont need THAT much... i swear by high grade semi synthetic, its road fuel at the end of the day, that shit kills engines quicker than poor oil... just rebuild it more often. simple. dont need to run so much oil it clogs up... too much and it leans the jetting out (if running premix, think about it, if 5% of your fuel is oil, your getting 5% less fuel, so effectivly by adding more oil your doing more harm to your engine as its running lean wiht lots of oil = no power)

    so ye, drop back to 20ml or 25ml at max to a litre... will run miles better
     
    MiNoR cOnFuSiOn, Dec 31, 2009
    #17
  18. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    ok, only put this much for the 1st litre because i thought there mght be a bit of petrol in the tank, when i actually fill up to ride ill run 25 per litre ;)
     
    rideorcollide, Dec 31, 2009
    #18
  19. rideorcollide

    rideorcollide Active Member

    Messages:
    2,122
    Rides:
    TYPH 172
    right, ive drilled the carb.. fitted vac nipple, blocked off oil, 115 main jet, needle clip on the bottom notch , idle screw 1 turn out and it still only runs on choke..

    is the vac from the petrol tank supposed to go straight to the carb.. and the one from the fuel pump meant to go to the reedblock vac??
     
    rideorcollide, Jan 4, 2010
    #19
  20. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

    Messages:
    14,276
    Rides:
    et2 monster
    yep.... if its only running on choke then ether theres an airleek or the pilot jet is wrong/blocked up with shit.. MAYBE its so rich the choke is actually leaning out the mix? wind the idle screw out a few turns (leans out the mix) remember to warm it fully up befor you attempt to ajust the idle mix and have it on a FAST idle..
     
    MiNoR cOnFuSiOn, Jan 4, 2010
    #20
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