Engine Trouble Splutering after 35k/h

[2strokejosh]

Hi there peeps need a little help,I've got a rock solid hp2 50cc ( has billet head, dellorto carb, head porting and new ngk plug cold one) and have ran her in about a week ago on my 4th or 5th tank now.
It is very smooth and responsive in the revs and when I was running it in I never went past 30 k/ph..
Now that its run in I've been starting to put the throttle down and its still verry smooth and picks up nice until it hits 35k/h exactly.. when it hits 35 it just starts sorta splutering like its top speed and its not even reving that much feels like there's heaps more to go..
if I hold it for a little splutering at 35 it Kicks in reving smooth for a sec or so but still doesn't feel rite.. I know its got way more in it as my old 49cc (had been around for years) went around 60k/h and sat at 45 pretty nicely, that was just an old untouched 49cc.
I am useing the stock cdi that I have had for years and a old bosch 8mm lead I was thinking it may be the cdi as its the only thing that hasn't been replaced and may not be keeping up at higher rpm? maybe a jag cdi or get rse to make me one idk?
Any help would be great! can't belive I just wrote that on my phone.. o . O
thanks heaps Josh.

 

[Deleted member 12676]

Sounds like you need to reduce the size of your main jet by one or two sizes. If you do that and the top end becomes right but then the low rpm power is weaker then you'll have to drill a miniature hole between the bottom of the atomizer column and the first hole. That's what I had to do with my Dellorto. Its a super great design that gives a more atomized mixture than a standard carb but lacks the ability to fine tune for each rpm range.