I recently purchased a 150cc GY6 mini buggy for $100 with the brand name JEHM on the gas tank. The buggy has not been started for 3 years and has been sitting outside, unprotected.

The engine is so close to starting but acts as though it's not getting spark. It just won't turn over.

I have installed in a brand new CDI box, ignition coil, spark plug, ignition switch, battery, and carburetor but the dang thing still won't start. I grounded out the spark plug and everything works there. We cleaned the lines and replaced the old gas. I can't figure out why this thing won't start for the life of me. The kill engine switch is missing from the dash, so we tried starting it with both the wires hotwired together as well as disconnected from each other. Still won't start. We removed the air filter, still won't start. Next I'm going to replace the wire harness, but if that doesn't work, I'm spent.

Does anyone out there have any ideas?

does it have spark at the spark plug? if so do a compression check

If the plug sparks while grounded then do as BigE said. You could also spray some carb cleaner in the intake and see if it fired. 3 years is a liong time to sit. You could have rusted rings or stuck valve.

Do a compression check and adust the valves, then check it again if it was low the first time.

The plug does spark while grounded. I've sprayed carb cleaner into the intake and nothing.

I guess I'll run to Sears and grab a compression tester. If it does turn out to be a rusted ring or a stuck valve, how much do you think that will run me to repair? And what is the difficulty level? I am just learning engine repair.

Thanks for all the help by the way.

A set of rings is maybe 50 bucks. I built my first motor a few months back. It seems harder than it is. If you do have to we can give you all the help you need. If you have spark and fuel it should fire. Maybe the timing is off and it's firing at the wrong time. Check all the ground conections as well

If your firing constant, take the plug out and pour some transmission fluid in it and walk away for a day or so. This will get your rings back in shape. Old shade tree trick.

Thanks for all the help. I really appreciate it.

I don't know much about engines but it really seems like the problem is electrical. Haven't run the compression test just yet. Gonna try the new wire harness first since it needs it anyway. The old one's plastic bits are all brittle and breaking apart.

The wire harness I bought was listed on ebay as a GY6 wire harness for a 150CC engine. Unfortunately it looks a tad different than what I have on there. I thought all this GY6 stuff was standard and compatible? On my machine there is a big blue cube that looks to be a fuse box that is attached to the harness which states "12V - 40 Amps". It rests directly above the engine in the mess of wires next to the starter. I have no idea what that fuse box is for but this new wire harness doesn't have a spot for it.

Are the 150CC Gy6 wire harnesses standard or do they differ from machine to machine? Working with this one is like wrestling a tiny octopus that's playing in spaghetti.

Why do you say, "it really seems like an electrical problem" when you get a spark from the plug? If the plug is sparking, that rules out an electrical problem, plain and simple. Now, that doesn’t mean it is sparking at the right time. So I agree with the others in this forum, start checking compression, valves and timing. The carb could probably use a little more attention too.

Also great advice on the Marvels Mystery Oil or should I say transmission fluid, which I am convinced are one in the same. If the compression is low, adding trans fluid or Marvels to the cylinder will “fix” your compression temporarily. At least long enough to get it running, if compression is indeed the issue.

Also, don’t forget that valve train. Considering what you have done so far, I think you should definitely remove the valve cover and make sure the valve train is still working. This would be a great time to find top dead center and making sure your overhead cam is in the correct position with both valves completely closed. Good luck!

Update. The plug is not getting spark now, which is so strange. It got spark the first time I tried it (just before I bought it). The engine was being jumpstarted from a car battery then, so maybe that's why???? But as it stands right now, it is not getting spark.

The reason I thought it might be electrical was because of the condition of the wire harness. It just looks awful. If you touch a connector, the brittle plastic literally turns to powder in your hand. That is the only reason I suspected it to be electrical. But I am just learning, and I honestly don't know enough about engines to back up anything I am saying.

Anybody know if the 150CC GY6 has a standard wire harness or do they all differ?

the wire harnes for each buggy is a little different main the connectors. double check all the connections and the spark plug boot