Engine won't start, runs only on choke and almost fully lean

[MotorBicycleRacing]

While I were fitting the carburetor back into the collector, my eye fell on this

This seems to be the only anomaly around the whole crankcase's gasket, how shall I proceed?

I know that I'll have to open the engine, and I'm kinda reluctant, I don't know how to proceed.

I might bring the motor to my trusted mechanic, which fixes any gender of bikes, and I'm sure that if I'll show him the problem,
he will get rid of it

Proceed and ignore it.
You might get some grease from the clutch shaft coming out
but that area is not exposed to crankcase gases.
Look at a pic of the cross section of an engine case online.

 

[gary55]

That could vary well be the problem, and if it's that far off there it may be off elsewhere as well. With the hole that far forward the gasket could be broke and leaking in the case as it is right at the transition from case to clutch shaft housing. Also with it that far forward the narrow portion of the gasket between the shaft housing and case may be that far forward as well and not sealing.Try sealing it there or use a unlit torch and blow propane on the suspected leak to see if it changes the way the engine runs. Here's what the gasket looks like at that area.
View media item 61452

 

[Otto Neumann]

Proceed and ignore it.
You might get some grease from the clutch shaft coming out
but that area is not exposed to crankcase gases.
Look at a pic of the cross section of an engine case online.

That explains why my clutch began to make a "quack quack quack" a bit of time ago

 

[Otto Neumann]

That could vary well be the problem, and if it's that far off there it may be off elsewhere as well. Try sealing it there or use a unlit torch and blow propane on the suspected leak to see if it changes the way the engine runs. Here's what the gasket l;ooks like at that area.
View media item 61452

I can't get my motor to idle, it runs exclusively in a prohibitive condition for a motor that has to be broke in (almost fully lean), and if I roll to a stop with the clutch disengaged, it dies out, I don't neither have the time to get off from the seat. At this point the problem should be that gasket, I checked any other gasket and everything looks just fine, except for this one

 

[Otto Neumann]

OOooh!!!

Now I see everything!

 

[gary55]

Try trouble shooting it as suggested abv. If it's at the narrow point between the case and shaft housing it will be hard to find. It looks to be nearly the thickness of a bolt to far forward. 6mm's forward at that spot would almost certainly have the narrower portion of the gasket below it inside of the case and not sealing at all. I could be wrong but that is what the picture is showing me and if I had a engine that wouldn't run without the choke and all else checked out well I would consider splitting the case. Eliminate all other possibilities first.

 

[crassius]

the case gasket used to always be a bit off, but not so much lately

as MotorBicycleRacing said, it probably makes a good seal where needed

if it is leaking a bit, you'll see oil stain there after a while and can address that then

if head gasket leaks, then you'll see oil up there too

usually, if it won't idle with idle screw all the way in, then it is too rich and dropping the needle can fix it to get you thru break in period

 

[Otto Neumann]

Try trouble shooting it as suggested abv. If it's at the narrow point between the case and shaft housing it will be hard to find. It looks to be nearly the thickness of a bolt to far forward. 6mm's forward at that spot would almost certainly have the narrower portion of the gasket below it inside of the case and not sealing at all. I could be wrong but that is what the picture is showing me and if I had a engine that wouldn't run without the choke and all else checked out well I would consider splitting the case. Eliminate all other possibilities first.

Thanks, I'll try to tighten up the head in a better way and give it a test, if it will not behave properly, I'll proceed to visit the mechanic and get it fixed

 

[gary55]

OOooh!!!

View attachment 83320
Now I see everything!

If your talking about that gap at the head it's normal. The inner portion of the head has a raised ring called a crush ring to aid in sealing. Just make sure it's torqued well I go 162 in. lbs.
View media item 60542

 

[Otto Neumann]

the case gasket used to always be a bit off, but not so much lately

as MotorBicycleRacing said, it probably makes a good seal where needed

if it is leaking a bit, you'll see oil stain there after a while and can address that then

if head gasket leaks, then you'll see oil up there too

usually, if it won't idle with idle screw all the way in, then it is too rich and dropping the needle can fix it to get you thru break in period

Until now I never noticed any form of leaks around the gasket, as I'm a 4 stroker, I'm just learning to play around with the needle x3