50cc 2 stroke engine poor compression

[Junior64]

Hello,
I'm new to the site and have problems with my engine. It began when I was riding at night and the engine stalled on me. Pedal my way home and notice the exhaust was blowing weak smoke and some of it was coming out at the chain transmission. I called my mechanic and said I might of blown a gasket around the crankcase. Just want to get a second opinion.
Thanks!

 

[LewieBike]

When you start the engine, is it turning over far easier when you engage the clutch while pedaling, that it was when new?

 

[Junior64]

It is now harder to start, I changed the spark plugs and the result is the same. Also forgot to mentioned that the engine bogs down on idle and have to throttle it to keep it going.

 

[LewieBike]

It could be anything then. I doubt it's compression if it's now harder to pedal against.

Are you using the 16:1 gas-oil ratio?

How many miles do you have on it?

 

[Junior64]

I'm using 16:1 mix ratio and it has 500 miles on it

 

[LewieBike]

You should go to using a 24:1 to 32:1 ratio. Use Non ethanol and some semi synthetic like Lucas or Motul.

These bikes call for a far too rich oil mix because the quality of oil in the Far East is generally a poorer grade.

What you'll discover is: when changing to a leaner oil mix, that now your bike runs much rougher because it's now running a far richer fuel mixture. It will be "4 stroking" which means it is firing on every other revolution when running under road conditions and loads.

You may have to open the carb top and move your metering needle's, ( in the throttle slide or piston..) clip up a notch or two. Do it one notch at a time. and test your bike afterwards. Be carefull as the tiny E-clip you move on the metering needle can go zinging off to the darnedest hiding places.

I do mine inside a gallon ziplock with my hands and pliers inside it, so if it does elect to fly off it doesn't fly across the room.

 

[Junior64]

I will try this later, however I noticed that there's exhaust smoke coming out from the chain transmission. Is that a problem?

 

[LewieBike]

It could be you have a leaking main seal(s). This could be a big job as it will require pulling the primary reduction pinion and (or) the the magneto coil and magnet. Pulling the right side gear cover off your reduction gearing and seeing if it smells and looks like gasoline has been leaking into it would be the first check.

Have you been adding a small, pea sized ball of good grease on the primary gears every few hundred miles?

It also could be that your clutch needs adjustment and is slipping and smoking a tiny bit. Slipping clutches tend to smell really bad like burning tar or tires, and they will smoke if there's too much grease on them. Doesn't exactly smell like a 2 Stroke engine exhaust.

 

[Junior64]

Will check the engine for the seals as they might be the problem, however the clutch is fine. It's located on the other side rather where the chain goes

 

[LewieBike]

Yeah it's weird that you're having smoke come out of that part of the bike.

Do you know about greasing up the clutch actuator/bucking bar and ball bearing on the clutch cover side?

You could be having smoke from friction of not having those parts lubed up well. It's pretty much required pre-setup on these bike engines.

Pull the sprocket cover and the bucking bar is an 8mm sized metal 'pin' or rod about an inch and a half in length, sticking out from inside the sprocket and clutch shaft. There's a 8 mm sized chrome plated ball bearing further inside, that the bucking bar presses on when you pull the clutch in. All of those mechanisms including the clutch arm shaft, needs to be heavily greased.

It also would be a good time to pull off your clutch cable and unscrew the clutch cable stop under your carburetor and force a few cc's of grease down inside the cavity under the clutch stop, then reinstall,

It will take some work to do all this but you shouldn't need to do it again in under a couple thousand miles.