ac vs lc 125 barrels porting (and lc ignition swap)

Discussion in 'Maxiscooter Tuning' started by seancullen, Nov 30, 2016.

  1. seancullen

    seancullen Member

    Messages:
    126
    Rides:
    et4 125,px80,dna50
    Hey guys, just looking for some info about this if there are any tuners still lurking about here.

    basically im interested in doing the lc ignition swap on my typhoon (and ac dragster)

    I understand the mikuni carb needs a slight upjetting, but just how much from standard?

    this got me wondering about the difference between the AC and LC barrels, bar the obvious cooling part. are they ported and tuned to roughly the same map or are they completley different cylinders internally?

    im also kinda wondering about the dellorto carb and airbox from the lc engines ive heard they dont really work on the ac engine but could this change with the ignition swap? if the porting of both the barrels are identical then i could see the dellorto stuff working without any issues. (ive got both sets to chose from at the moment but havent actually done any experementation with running them yet)
     
  2. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    LC is built to a closer tollerance due to it being a water cooled system so its said they make a little extra power from this, port wise i would say they are near on the same, ie in degrees and layout . sitting for an hour in still traffic the liquid cooled motor can see temps rise as there is no airflow over the radiator to help convect heat away ( not like we dont filter traffic jams)
    if the water pump fails in the closed loop system your in some trouble, temps will shoot to the roof and the water will start to boil , replacing means tearing out the pump fitting new parts and then getting it sealed water tight.

    AC is more simpler with less to go wrong , if the fan fails its a simple remove shroud bolt new one on and way you go, so its less of a tear down. i would also say theres less tollerence built into ac cylinders/heads , in traffic the same the motors gonna overheat if that fan cannot spin upto its optimal flow rate rotation, but its aided in a way by heat convection to having the larger fin surface area to allow heat to convect away
     
  3. seancullen

    seancullen Member

    Messages:
    126
    Rides:
    et4 125,px80,dna50
    ah okay, i found out today that the pistons are not the same part number, so it is somewhat possible they are not the exact same however i would wager that they are not too different even at that, that lower tolerance could explain the need to slightly upjet these to prevent detonation on the typhoon engine then?

    might also explain why ive been told the dellorto dont run properly on a typhoon, could be already at that slight bit richer to account for the higher state of tune, will investigate this more when i have the dragster engine in.
     
  4. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    5,466
    following this thread...
     
  5. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    lc piston would be built to a higher tollerence , so in a ac could be a little bigger or smaller.

    carb is a carb if its set up right, thats always what i have thought. like a hemi big block you can throw on stock carbs from factory or a set of webbers as long as they are set up correct to give the maximum fuel rate required to the motor it should work.
     
    scubabiker likes this.
  6. seancullen

    seancullen Member

    Messages:
    126
    Rides:
    et4 125,px80,dna50
    Thats what youd think alright, but i definitely heard/read somwhere,
    possibly even on an older thread in here that the dellorto and mikuni carbs are not a straight swap(I assume theres no reason it couldnt be jetted to run right)

    I havent done any experementation myself to confirm this year so ive been trying to narrow down the reasons why this would happen on 2 engines that are identical bar their top ends.

    if the top ends are fairly identical bar tolerance's and cooling system another theory I have is could the air boxes have somthing to do with it? the LC airbox is a lot bigger than the AC one so perhaps the carbs are set up best to work with these from the factory, Luckily ive got one of each to play with :)
     
  7. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    5,466
    what he said, a carb is a carb, as long as its dialed into the engine it will work.
     
  8. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    possible but a larger air flow just means you have to either up the fuel amount to be in that golden 12-1 -13-1 ratio, anything about 14-1 is going to be boardering seizure limits. or somewhat start to restrict the extra flow with baffling or a restriction inside box.

    Another thing is this you can only compress so much air and fuel in the cylinder before you either hydrolock or blow the seals . i would say the alrger LC box is due to it being able to make more power at a more stable temp range than the ac setup. adding the lc box to an ac motor just means your need to upjet a little more to compensate for that extra airflow you now have.
     
  9. seancullen

    seancullen Member

    Messages:
    126
    Rides:
    et4 125,px80,dna50
    interesting so im wondering will the delly and larger airbox be able to just bolt on and go with the lc ignition then,engines in the drag now, will investigate when i get a completley running stock engine as a baseline to work from, shouldnt be too long :)
     
  10. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    lc ignition is going to be a differing curve compared to the ac ignition, not a good swap in my eyes. your running a differing timing and possible advance to given the lc will produce that little extra go . could find the lc stator and likes is differnet to the ac to the looms will be for a start , as your reading heat temp sensors and the like also.
     
  11. seancullen

    seancullen Member

    Messages:
    126
    Rides:
    et4 125,px80,dna50
    just an update since i finally got around to doing this mod recently on another scoot, as the drag has been shelved until i can afford to do a proper job on it, I havent tapped the threads for the flywheel yet so i havent driven the bike more than up the street and around the garden.

    First impressions cold starting is now a little easier, the scooter just feels a good bit more responsive now and any lag which might have been introduced when going full throttle from a standstill of very slow has now been reduced and greatly dimished (although it was never bad on this engine anyway it was there and noticable)

    pipe seems to be warming up fast so im a little weary of this until i start to investigate the jetting, and its half to be expected since i havent been able to attatch the fan to the flywheel just yet, overall im fairly impressed so far, and thats only really with half a mile of driving on it to see how it would run.

    Also noticed that my flywheel side oil seal is looking a bit sorry for itself and might not be long for this world, so that needs to be added onto the project to do list whilst i got the flywheel off to tap threads.
     

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