Hey everybody, I'm a new guy to the 4 stroke world lol. I had recently got a bike with a gy6 that ran fine, but needed a belt. and I was messing with it in my garage ( changing oil, plug, cleaning carb, etc.) and it still ran good, and as it was running it just kinda died, so I checked all connections, it's still getting spark, it's getting fuel because when I hold my hand over the carb its wet with gas. So next step to solving the problem... valves. I checked and re-adjusted the valves to factory recommendations, and as I was trying to start it, it sounded like it was running, but only while holding the starter, and when I pulled the throttle to WOT it still wouldn't start. I cant think of anything else to do to it. I need help lol
Post by wyopaniolo210 on Feb 13, 2014 14:20:15 GMT -5
I agree, it sounds like compression. However, go back and make sure your spark plug is in tight (don't over tighten it though) and double check your valve clearance as both of these can lead to loss of compression. Make sure you're at Top Dead Center (TDC) by lining up the T on the flywheel. I usually do 0.003 inches on intake (top valve) and 0.004 inches on exhaust (bottom valve). Yeah it might sound obvious, but in my experience with these 4 strokes, being off even by a little on your valves can make a big difference.
If it still doesn't fire after that, try taking the carb off and spraying starter fluid straight down the intake and try to start it. If it fires, you have compression and spark and you need to make sure the fuel is actually making it all the way into the cylinder. If it doesn't fire on starter fluid, you know at least either compression or spark (or both) need to be fixed.
Hey guys, I tried everything you guys told me, No luck! But on the bright side I scored an 80cc bbk. I also noticed when my bike WAS running, I had brake lights, head lights, blinkers, dash lights, etc. and when it was running all my lights just kinda went out?? and I just did the classic 'tap on things until something happens' trick and my dash lights flickered and a corner light on my headlight, and my high beam light came on, then went out again. still no blinkers, nothing.
-EDIT- And since I had ordered my 80cc bbk, I was removing my jug, head, etc. and my piston looked slightly scored. and I could put the piston back inside the cylinder, and hold my hand over one side and push the piston through and I could hear air seeping through the uncovered side. SO, having said that, It has to be a compression issue lmao.
Alright, so it was a compression issue, I got my 80cc bbk on the bike and she fired right up! but broke the belt not even a mile from my house. I'm assuming my rollers are worn because when I pulled the front part of the variator off the rollers were sideways and some sides were flat.
Post by junkyarddog on Feb 19, 2014 2:38:57 GMT -5
I'm wondering how a compression issue developed while it was just sitting there running. You said it was a GY6, but that you got an 80cc BBK. I thought a GY6 was 150cc.
I have been fooled by compression problems a couple of times, just going by feel. I wasted a lot of time fiddling with the carb/fuel system. If I have any reason to suspect a compression problem, I now check it with a gauge, to either confirm it or rule it out, before moving on. An engine with some compression may fire on starter fluid, but won't run. Many engines with borderline compression will run, but not develop much power. If there is damage to the piston/cylinder, there has to be a cause, and you need to find and correct it, or it will happen again.
3000 miles really isn't anything. How long have you been running on it with a broken speedo? There was a thread a while back about the miles people got on scoots, and if memory serves me correctly you should be able to get 10 - 15k on them if you take care of them. In other words check valves regularly, change oil, run at correct rpms ect......
I might be off a bit on mileage, but my 2 cents is take care of the gy6, and it will do ok.
2009 Kiat Velocity GY6 150CC
SS braided brake line, 14g roller weights, Uni-filter, Orange coil and wire, Fuse block install and bike re-wire, 11 pole stator upgrade.