increased intake duration=upjet?

It seems very logical, but I want to hear from someone who has done this.. My setup:

50cc tccd ported

16mm phbg dellorto-68main, 48 idle

16x45 gearing

timing full advance

20mm intake

high comp head-180psi

bullet pipe

50mph . The bike runs great when I first fire it up. Good acceleration, midrange, and revs pretty high. But when it warms up, it stars bogging really bad at takeoff. This kit was 100 bucks, so I'm using it as my guinea pig to learn about porting, timing etc.. so if I turn it into a paper weight, it's not that big of a deal to me. Im learning a ton. So anyways, I read graham bell and jennings, and I decide to cut my piston skirt to increase my intake duration to get more power up top. I took 2.5mm off of my intake side of my piston. Results= slower takeoff, weaker midrange, and I lost about 3mph. Not what I was expecting. So I wanted to see what it would do with a 21mm del, so I throw it on, jet right (76 main, 38idle), and I'm off. gained a couple mph back and have even better midrange than with the 16mm. But the lowend is horrid. Bogging really bad. Have you guys seen power increases with this kind of mod? My bike accelerates hard from 37 to 49, and then feels like it hits a wall right at 49mph. Right at 11k rpm. Will not rev higher. Did I take too much off of my piston skirt? Was thinking about taking a mm or 2 off my cylinder and raising my ports up, but I'll save that for another thread. Advice about mods that you have done to get more power out of a 50cc setup like this would be much appreciated. Thanks..

Re: increased intake duration=upjet?

Did you solve the problem with bogging after it warms up?

I'm having the exact same problem, both with a 12mm Bing and a 19mm PHBG with my 50cc treats kit. :/

Re: increased intake duration=upjet?

someones pants are on fire!!!! 50 on stock gearing, no.

Re: increased intake duration=upjet?

Yes. 50 on stock gearing. no i didn't figure out the bogging yet, Im sure its just a jetting issue, my question is about the piston modification.

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