1978 Yamaha Enduro 100 that won't start HELP!!!

[Zechariah]

Hey everyone,

I've got a 1978 Yamaha Enduro 100 that won't start

I've done the following to it:

-checked the compression 120psi
-cleaned the carb out
-put a new battery on it
-and put fresh gas in
-checked for spark
-checked the reeds
-took the exhaust pipe off and dumped about half a quart of oil out of it (Yikes don't know how that got in it do you?)
I got it running for about one minute the other day and it sounded great and smoked a lot then died and now it's flooding and won't start, I am really stumped now, can anyone tell me what else to try?

Thanks.
~Zechariah

[MagicRat]

The oil in the exhaust may be from the oil injection tank. Check the tank and make sure it's got 2 stroke injector oil in it. Sometimes the injector system leaks oil into the engine and out the exhaust if the bike was stored for a long time.

If it does have such an injector system, use straight gasoline, not pre mix.

This would cause all the smoking you saw. IMO you will need to run the engine for at least 20 minutes before all the oil is burned off.
Because the engine and crankcase is saturated with oil, expect it to oil foul the spark plug a few times in that 20 minutes.
So, try changing the spark plug with a new one. If/when it oil fouls again, remove it and clean it up, install it and try again.

[Zechariah]

Alright well I got it started.
It was the spark plug although it looked like it was new it was malfunctioning and not giving a good spark (I found this out by taking the spark plug out and turning it over, the tip wasn't sparking, but there was some little sparks come from around the tip.) so I replaced it with a brand new one and it started right up.

Now with it running I get this constant clacking noise coming from the engine,
what could that be? I am not positive that the oil injector is working (should I just plug the hose and try a fuel mix? could this be why it's clacking?)

Any help with this problem would be greatly appreciated.

~Zechariah

[MagicRat]

Well, if the injector tank is full and there are no air bubbles in the oil line then assume it works, and do not bother plugging the line.

As for the plug....... 2 stroke engines are notorious for using up plugs pretty quickly. It's not unusual to benefit from a new plug with as little as 20 hours use.
Get another plug as a spare so the next time it is hard starting, try the new plug first.

As for the noise, are you used to air-cooled 2 strokes? They tend to make lots of engine noise because there is no water jacket to dampen the sound, and the cooling fins act like a loudspeaker for the engine.

I expect given the age of the bike, the piston and rings are probably pretty worn and loose, so the noise is probably 'piston slap'. 2 stroke engines do not last as long as 4 strokes, so it may be time to remove and rebore the cylinder and install a new piston and rings. Unlike a car, this is an easy job on an air cooled bike.

[Zechariah]

Alright thanks the injector is working, thanks for your help.

~Zechariah