I have a 17.5mm carb (dellorto PHVA) that runs with a good mixture when I have my standard airbox mounted (92 mainjet). When I simulate to go with open airfilter (just take away the airbox), it just bogs when I hit the throttle. Therefor, my main is too small. But before I spend 100$ on 20 different mains, I want too hear what main you think, so I can come close and dont need to spend more $ than needed. According to Dellortos magic number, I should have mainjet 88 (17.5*5), and this is correct if I have original airbox with airfilter (92 main is good if I take out the airfilter). Please dont give me an answer that its got too much air and so on. If I let the carb have the amount of air that it can take in, then its my job too feed it with fuel. The carb cannot have too much air.
Like I said on the other thread, airboxes are complex things, I had a customer who just HAD to have a sports filter on his aerox, I had a 120 jet in there, bored out to about 130 then had to tape up nearly the whole filter... The only time I use sports filters is if I cant use an airbox, or for high end racing engines....
What carb was that? 17,5 aswell? Im not going with open air, but that Will give me a good guess of what I need.
Great to know, thanks! Have 92 main in and its not near to bog... the cylinder I have (70cc) seems to need a lot of candy to go to topspeed. (Original airbox with no restriction)
