Hi, i have just purchased a dellorto phbg 19mm carb to replace my 17.5mm carbs the bike and specs a zip sp with mhr rep 70, yasuni r, polini filter anyway my 17.5mm was running a 112 main jet so i tried all jets from 100-120 on my 19mm and no luck at all just bogging out on full throttle but i just thought id try the 72 tht came with the carb and it ran a lot better, i no this is probrably very lean so i dint run it for long im just thinking its starnge downjetting when going to a bigger carb so im wondering if the needle settings wrong as its currently on the top clip/ lowest point, am i going wrong anywhere?
yes, the mainjet was STUPIDLY huge wiht the 17.5 in the first place... this was down to the incorrect rollers being installed, the problem has been exagerated by a larger carb... start out wiht an 85 ish jet and drop some weight off the rollers. everyone thinks this is "bogging" fact is an auto engine needs a silly big jet or bad idle mix to actually "bog" out... the thing your exxperiencing is transmission stall... lower your roller weight, needle at top notch, 85 ish main jet (to start) and drop down from the stock rollers (assuming youve never changed them) to around 6g (could well be lower) if its not revving and "boggin" its amlmost cedrtinaly bogging out... id be supprised if the kits still in good nick after you ran it wiht heavy ass rollers and DOUBLE the stock jet SILLY big. ive never used a 112 on a 50 even wiht a 28mm carb its ALL rollers m8, sort that then worry abut the carb. lots of usefull guides in the guides section. worth a read
