Motor good at half throttle but bogging at full??


New Member
May 18, 2023
Kind of lost as to what’s going on, I have a reed valve + windowed piston on a 80cc 2 stroke engine. I’ve got an HP carb with a #70 jet installed. I can ride the bike and when I first start riding the idle is fine but when I get it going to WOT and then come to a stop the idle is really high. I also have the issue of my bike bogging out when trying to get to wide open throttle, half throttle is fine but as soon as I turn it past the whole bike slows down and starts 4 stroking. My reed valve screws kept backing themselves out so I put threadlocker on them and it hasn’t been an issue sense. I tried messing with the air/gas screw and it has no change. Any ideas? Pictures below ⬇


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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
Los Angeles, CA.
I concur with Larry... That carb is junk, & you'll be much happier with a stock carb!
The main problem you're having is the jetting is too small... Whenever you have a reed valve you need to 'throw gas at it'!!!

Get the stock carb & install a much bigger jet. ;)

Larry Trotter

Well-Known Member
Nov 26, 2017
I have had carburetors that never could be made to work right. Your observation that it idles normal when started and then really high after it has run some would be a really big clue that it’s got an issue. What’s the bolt pattern on the adapter that goes from the carb to the 4 bolts on the reed assembly? I have a couple of flange carbs and an adapter that might fit.