Just fitted a 70 kit and 21mm carb, running like a bag of bolts lol. The carb has a 90mm main jet which is the smallest size which came with it. What should be a rough size to work from? mid 70's down? The bike is running rich and also black deposits come from the exhaust, I have found winding the air mixture screw all the way in helps but it still just about runs. The bike is running premix (40ml castrol synthetic ester to 2l 95 ron) I would book it into taffspeed but at £70.50 an hour id like to get it close myself. Any help appreciated
You have the same problem as me I have a 86 jet in it at the moment and haven't a clue whether to go up or down :msn1: Have searched through all the jetting threads and can't find anything as we have near the same set up. I have a 70 jet and it didn't really like that.
ok you both have different bikes so jetting will be completely different, trust me it will!! although for both, the air box will need to be modded. ive tried and tried to get it running ok without modding it, but for the time and hassle its not worth it so just get a dremel/knife/drill out and start cutting. the carbs are normally provided with a template showing where to cut and there pretty accurate too for the piaggio drop the needle height down by two notches, and set the idle mix 1 1/4 turns out, forget bout touching the idle just yet, it should be set fine. main jet should be bout 70ish with an airbox and bout 85ish with air filter for the aerox i usually drop the needle height by one notch, set the idle mix at 1 1/2 and main jet wise with an airbox its bout 80ish and with filter ive had a 90ish jet running perfect
Fitted a 72 jet with a 40 pilot, an its running really good, could do with a little tweak of the rollers/clutch springs/carb but otherwise its pulling like a train
Cheers for the help. The idle mix doesn't do anything when I turn it right the way in or right the way out :rtfm: Sorry to be a pain in the arse but I'm not too clever with carbs. How do I adjust the needle height? Cheers.
Undo the screws on top of the carb (or twist dependin on carb). Pull the throttle cable out completly. Remove the slider and spring etc to leave just the cable. Then look at the needle and there should be a small clip. This is what you move up and down. As for the idle screw make sure the bike is warm, leave it running. As you wind the screw in/out you should notice the revs rise/lower slightly.
IDLE MIX screw thats the idle minor said to wind the idle screw all the way in and then undo the idle mix screw untill the revs sound at there peak, then you can adjust the idle setting watch not to lose the clip on the needle aswell im always dropping the little buggers!!
Ohhhh. I know now. The needle from the top of the carb with the little white circlip?? I was always fiddling with it when I had my pitbike. Im running a 86 jet with open filter. Still running like a bag of shite. Think it may be my reeds as they do not lay flat on the block. They are about half a mm up. Could that be it?
have you changed your rollers, im guessing no... jetting wont make a bike not run unless its severly rich/lean (altho lean usually runs an goes bang where as rich doesent like to rev but will still full throtle) sort ya rollers with the carb as is.. will get it ridable enough to sort the jetting how many times do i have to say it, transmission THEN jeting :rtfm:
does it ride fine full throttle for a few yards then drop revs? if so no its not enough... should run fine with the 90 jet so your "running rich" identification is probably too heavy rollers
I had this problem when i installed my 21mm carb a couple weeks ago... listen to minor.... lighten those rollers..... i lightened the rollers...and it ran on a 90 jet.... (was really rich....but still ran fairly well).... with the rollers i used before, it would bog down when the clutch was trying to engage..... lots of smoke...coughing, spluttering etc..... now running an 80 Jet and open filter....tune is still not perfect, but runs pretty well. my new jets arrived yesterday, so ill retune it to run an airbox.
I wasn't disagreeing with him. I was saying no to the question "does it ride fine full throttle for a few yards then drop revs?" Cheers for the advice What weight are you using so I can get a rough idea? Cherers.
ive got a polini 9 roller variator.... at the moment ive got 3x4gram rollers and 6x3 gram rollers.... ill get a set the same after i get my pipe.
yeah... for me ill try and get some 3.3g rollers.... but for you...i dont have any experience with the 6 roller ones... so im not sure what to suggest.....
Well I went and got some 4g rollers today. Put them in, took the plug out, dipped it in a bit of petrol, cleaned it with a wire brush then cleaned any excess petrol/oil off with a cloth and stuck it back in. Went do the road for about 30 seconds 1/2 - 3/4 throttle as it was still a bit cold and it was coughing and spluttering a bit, then it started to clear its self a bit. So I turned around and opened it up, it cleared itself completey and it fucking flew!! the first time it has run good since I have had that bore on it... And fuck me it does an half pull!!!! Cheers for the advice :beer:
