My Newporti is a 1.5hp with a biturbo.. the original jet for that engine was 50 I upjetted to 58 and it ran ok but when I tried a 60 and removed the plug in the back of the airbox it made a huge improvement.. the plug is the key.. if it's out it wont run at all with a 58 and if it's in it dies with a 60.. its tricky and believe me Ive tried like 30 combinations 12 &15mm carbs with 12/15mm intakes.. I found the smaller 14 intake worked much better but either carb is fine on that engine... aand the HI perf air filter works great with the larger jets...
I tried upjetting the Newport from the 60 to a 62 but it boggd bad... 60 is the largest it would run with.. but it screams now... mebbe youre overjetted and the warmer weather is makin it run richer?
now the magnum is a different story.. mine is driving me nuts at the moment..
I'm having the same problem.. I just put a Biturboon the Magnum and changed the carb to a 15mm Bing which I upjetted from 60 to 62,64 and finally 68. I have a Hi perf air filter too.. the problem is my manifold is only 12mm and it's the tall one no one sells 14/15mm for so I have to bore it out... but untill I do it will boggs at every setting..
BUT when I put the 12mm Bing back on it with a 68 jet it runs awesome.... smooth acceleration and shifting with a full throttle from a dead start... I did a plug chop and it was whitish gray so it's running too lean so I ordered the next few larger sizes and I'm not running it till they come..,
The thing thats driving me nuts is I'm wondering if I upjet the 15mm to an even bigger jet if it will smooth out.. or if the 12mm intake is just too restrictive to let it run properly. I pulled both carbs today and completely cleaned them and reassembled them.. I reek like carb cleaner and gas lol..
If anybody has any suggestions I'd love to hear them...
Fred... sorry I spaced out on the Middle East show.. I remembered it on Sunday DUHHH I was so pissed at myself.. cause I love that place and would have definately come if I remembered.. too may gas fumes I guess lol