That makes sense. I'm not happy about it, but it makes sense. Time for more troubleshooting.

 

Keep us updated as this crankshaft/flywheel has me wondering. Most all Chinese/Taiwan 2 strokes kinda revolve around the same patterns on cranks,cylinders,and other mechanical dimensions on the 50 and 90 engines,but this one is strange if the flywheel wont snug up ??

 

Messed around with it a little this morning. The old and new cranks are exactly the same size except for an EXTREMELY slight difference in angle of the sloped cut from the threads to the machined shaft. I guess that's enough to make the difference.

Anyway, I took out the plastic gear used to turn the oil pump, and the outer snap ring since I am not using the oil pump anyway. I was able to get the flywheel slightly snugger on the crank. It's still not tight enough to require the puller to remove it, but it is snug enough that I have to work a little to pull it off with my hand.

Fired up the bike, most of the rattle noise was gone, rode it round the yard for about 2 minutes, loud rattle came back, lasted for about 30 seconds, went away. Bike was back to as quite as when I started it.

Rode it around for 11 minutes, and it shut off. Would not restart for 20 minutes.

And to top it all off, I had a new problem show itself this morning after riding it for several minutes, the throttle seemed to "stick". The throttle lever returned to its idle position, but the rpms still stayed high enough to make the bike move on its own AND none of the kill switches (tether, ignition, or handlebar switch) would shut off the engine. It did not do this every time I applied throttle, but it did it enough to be a problem. The only way to get it to return to idle was to hold the brakes for several seconds, then it would drop to idle. It did this several times...sometimes the kill switches worked after the idle dropped, sometimes they didn't.

What the heck would cause the kill switches to not work ????

 

Well, with the help of OPT, I'm getting closer to having this thing road worthy for the grand kids.

Put the new coil on yesterday, and rode it around the yard for almost 30 minutes with NO cut off problems !!!!! And again this morning...YA !!!!!!! I was hoping this would be the solution despite the old coil testing ok.

HOWEVER (there's always a "but"), I still have the issue of it just accelerating on its own, and none of the kill switches working when it does. I actually rode it enough this morning to describe it a little better. After about 10 minutes the speed would "stick" some, and I was able to move the choke to get it to idle down. So naturally I thought maybe the choke was sticking, but didn't see anything strange. After riding it some more, the throttle eventually just stayed at a "high idle" and I could not get it to idle down. I didn't need to be moving either. I could be sitting perfectly still, and it would idle up on its own. I still don't see anything that looks like its sticking, but I didn't pull it all the way down yet. The warmer the engine gets, the worse it gets.

The more I think about it, the more it sounds like it's leaning out as it gets warm ?? Air leak ?? It's possible I nicked the crank seal on the stator side of the crank when I was installing it. Is there a way to test that ? Spray something on the seal while the bike is running ? Can I change that without tearing down the engine again ?!?!?!?!?! That's the only questionable area I can think off, but I'll recheck the torque on the case bolts too.

The thing that confuse me about this:
When it's stuck on "high idle", none of the kill switches work at all. I had to pull the plug wire to shut it down. I thought the purpose of all the kill switches was to shut off the engine in the event of trouble.

I found on another forum where a guy was having an issue with none of the kill switches worked after the bike warmed up (he wasn't having any "high idle" issues). He said his problem was a bad ignition switch. If that was the problem, why didn't the other kill switches work?

And my final issue (for now, lol), isn't this thing supposed to have a working tail light? The brake light works fine. I put in a new bulb and still didn't have a tail light. The wiring from the tail light has 3 wires (I assume a low side, high side, and ground). The plug from the bike has 2 wires..a constant hot, and a ground. I assume when you apply the brakes, it completes the ground circuit ? Why wouldn't it have a tail light ?

 

Okay now... Does sound like an air leak or perhaps the carb slide is sticking in the bore that you might want to check out. Plus the black wire from the cdi is the kill circuit to the cdi. You can trace any wiring there back to the ignition switch. As stated the ignition switches can go bad,plus you can pull the plastic boot back from the ignition switch and see if any connection has come unsoldered. I've found that a couple times. You can change seals without having to split the engine,BUT sure would help if you could get a leak down tester to help eliminate the problem. Could be the seals leaking,base gasket,intake manifold,head gasket,or even the crank case itself sucking air. And yes if it gets to "screaming" when it's hot,then at times NO switch will always stop it because it starts the "dieseling effect". That is the cylinder/piston can get so hot, just the heat from it will keep it running when fuel is drawn in and will keep igniting as long as it has fuel and air. Not good on the engine as you can imagine. I had that happen on several dirt bikes and watercraft over the years. You only have a brake light on the older ones that work off the plunger on the left hand brake. It's a combo starter interlock/brake light plunger.

 

Thanks OPT !!!

Nice info, but I don't have the equipment for a leak down test. I guess I'm using good old soap and water, lol.

I'll try to spray some water on it tomorrow. We're getting ready to head out for a weeks vacation, so I might not have time. I'll post back if I get it done.

I know engines will diesel if they get to screaming, but this isn't screaming. It idles high, but not that high. Honestly it's really just enough to engage the clutches and roll about 5 mph. And, the kill switches work fine until I get the high idle syndrome. I guess I'll be tracing some wires, but it still doesn't make sense to me. I'll try to hit one of the kill switches as I'm accelerating to see what happens. If it works as designed, then I'm assuming that issue is likely associated with the air leak (if I have one).

I've got to figure a way to wire the low side of that tail light. I want a tail light on it. The wire is already there. I just wasn't sure exactly how to do it since it appears the brake light is ground activated. Would just wiring it to an ignition hot, and ground to frame work, or will that mess up the other wiring if they are ground activated ?

 

Don't think I'd try to get a tail light as you could cause more problems,tying into a hot wire. Brake lights were just mainly to alert anyone riding behind and Polaris at the time thought that was all that was needed.

 

While Surfing the site, I realized I had not updated this. So here it is:

I ended up pulling the engine back out, and tore it all the way back down. I discovered I had nicked one of the crank seals when I installed them. So apparently as the engine warmed up, it made the split open up and the engine run lean...thus making the engine "high idle". I never did figure out why none of the kill switches would kill the engine as the rpms increased.

Don't know why the flywheel wouldn't snug up, but it snugged up appropriately after I reassembled the engine.

The rattle noise I kept hearing was the top edge of the piston hitting the head. Luckily, it did not damage the piston beyond use. I saw this when I tore down the engine, but wasn't sure why it was happening. A little research and I discovered there are a couple of crank/ rod assemblies available for this engine with different strokes. So naturally, I thought I might have ordered the wrong one. However, according to the number stamped on the crank, I have the right one. Anyway, took the new crank assembly, old crank assembly, old and new jug, piston, and head to a machine shop. He found the new jug was slightly shorter than the old one. He machined the head's bore to match, everything works GREAT.

I never did figure out the tail light not working. I'm almost positive it worked before I tore everything down. Either way, not a big issue for right now.

The only "issue" I have now, is that occasionally the float will stick open and flood the engine. After pulling off the bowl, and spraying the needle with carb cleaner, it works fine for a couple of weeks. I guess I have some dirt in the system somewhere, but don't know where. The tank has been cleaned twice, and it has a brand new fuel filter. Either way, small issue in the grand scheme of things.

 

Glad you finally narrowed down the major problems to the seal and the head/cylinder. Tolerances on the Taiwan/Chinese parts can vary from machine to machine,one of the reasons I was leery on ordering after market parts,even if the parts are way cheaper than oem. On the switches not killing the engine,I've had that happen on some two strokes and water craft when they ran lean. They get hot quicker than you realize and nothing hardly outside of choking down the air supply will kill em.Scary thing if you ever have one run wide open! As far as the carb float sticking open,you might check the clearance on either side of the float arm to the float arm posts. You can file a little down on one side of the float arm to allow a little more slack,might help on the float sticking.If it doesn't help,these carbs are cheap on Ebay.

 

Well, I probably jinxed myself with that last post. Had the grand kids out yesterday, and it just died. She was riding along, and it just cut off. It's getting fuel, but doesn't seem to be getting fire. I pulled the plug and grounded it to the frame. I can't see any spark on the plug, except every now and then. And then, it is a very weak spark. I haven't put a meter on anything yet, but I replaced the CDI and coil with known working units, and it still won't start. Like I said, haven't tested the stator yet, but the electronics on this thing only has about 40 hrs of riding. It better not be another bad electronic item !!!

I thought I read somewhere that some people had issues with either the ignition or handlebar switch that wouldn't let the machine start. Anybody know which wires signal (I assume the coil) to energize ? Is there a way to bypass the switches to isolate the issues ? I'm not sure if this is true because the engine will spin, it just won't fire.