Bored/stroked gy6 bogs at full throttle

Posts: 13 · Newbie Joined: 07 Jul 2008 Posts: 13 Pictures: 0

hey everyone my blade was running perfectly for 2 consecutive hours after the stroker crank install.... but for some reason when I give it full throttle the engine wants to die. I can however accelerate slowly but it just lacks power now. I even put the old jet (127.5) back in, but it still did it. I am thinking that my valves need adjusting since it backfires after I let up on throttle. Would my valves need to be set to different specs than a stock gy6? -Jerad

Posts: 4307

check your plug, most poked and stroked gy6 engines need a BIG main jet. I have sen as big as a 190. change the jet before you run it much more or you could run it to lean and burn it up

Posts: 13 · Newbie Joined: 07 Jul 2008 Posts: 13 Pictures: 0

Well I am currently running a 140 jet in there... hmmm.... I just cant help but think it's something besides that sine it ran fine for the first two hours. I am not saying that I don't need a bigger jet, but it bothers me that its just now doing this thanks for your response. -Jerad

Posts: 201

Your jetting is too lean,what type carb are you using,if its stock you may have to go larger like 30 or 32mm.My sons kart has a 2mm stroke and 62mm hole and and a 30mm carb,we currently have a 174 main jet,and plenty of power at top end however it will pop out the exhaust when you let off the throttle at about halfway down the power curve.This is due to the slow jet being lean.We had to take a 160 main jet and drill it to the desired size. The slow jet I have two larger sizes and are in the process of working on it.First though you will have to get the main jet right.Your plug should read a medium brown,now to check it you need to take your kart somewhere you will be able to make a 100yard sprint.The important thing to remember is that you don't want to read a plug with any idle time on it.To accomplish this ,take your kart to a spot with a 100 yard strait and flat,accelerate to full throttle for the 100 yards +or- a couple feet,while at full throttle cut the engine off while holding at full throttle untill engine kills than stop and pull plug to read,it should be a medium brown,if not increase the jet size until the brown color is reached. When the main jet is correct you can than work on the slow jet,this is probably your backfire out the exhaust when decelorating.Be patient and take your time and once you get it right its done.The size of jet will depend on your bore size,cam size ect.