Where is the Crank Gasket?

In my previous post I was having electrical problem with my bike I have since changed my CDI now the bike runs again, ( but it stall immediately instead of idling and runs hot) but on on of my cold start attempt the bike backfired but not very loudly.

Someone suggested that it was the crank seal which could be carefully pushed back in with a flat screw driver

I have one small problem were is the crank seal???

Marc,

There are 2 crank seals...one behind the small gear on the clutch side, and another behind the magnet on the magneto side.

Remove the clutch and magneto covers and look to see if either one of these seals appears to be standing out. They should be flush with the engine case, or slightly recessed. Use a flashlight so that there is no doubt.

Jim

How do you undo the small main cog? Do you use a flat head and turn it in a particular direction?

Yep turn the big screw in the middle of the cog anti-clockwise while holding the cog in place.. but be careful not to damage the teeth of the cog. Then it should just pull out with little effort. Good luck..

Is there a special type screw driver to buy to fit that big screw in the middle?

Its hard to turn with a normal sized screwdriver, get the biggest one you can find probably the long handle type will do..

....or find an appropriately sized flat piece of metal, and put it in the slot and turn it with a large adjustable wrench.

Use a piece of leather or heavy cloth between the gear teeth to keep them from moving.

__________________
If it ain't broke, and you mess with it long enough, it will be.

Also, check for an air leak in the usual other areas....intake and base gaskets, intake to carb junction, ect.

__________________
If it ain't broke, and you mess with it long enough, it will be.

Did it in 5 mins to take it apart...The flat head looking screw in the middle of main cog is not flat..Its flat on the ends then starts to get deeper as you go in the middle..It's a bit like a slight V shape which makes putting the largest flat head screw driver in hard and slip easy. What I did was chocked it with some riggers leather glove between the clutch ring gear and main cog, got a screw driver thats roughly half the length of the screw, put it on the end of screw , got a hammer and gave it a light tap anti clockwise direction. This was enough to unscrew it over by finger pretty much. Then I took the star washer out that sits in ther, used a sprocket remover tool that came with my engine kit which is similar to a harmonic balancer removal tool. That pulled the main cog out easily. What you have to watch for is that on the shaft, there is a little key which holds the sprocket to stop it from slipping. Don't loose, if it comes off with the cog like mine did, just press it back onto the shaft with the semi circle bit into the shaft and the flat bit on top. Use a flat head if you need to press it down more.. The new seal can pretty much press in. I didn't have to remove the clutch cover/ring gear to get it on as it's not that much in the way..Installation is basically reversing the removing procedure..Also put a light dab of grease or 2 stroke oil on the new seal so it slips into position easily. Don't over grease it, just very lightly...