snapped backplate screw - ok??
 

hi all,

i decided to pull apart my 353-09 and one of the heads of the backplate screw snapped off. the remaining thread of the screw is deep inside the engine case body, and there is no way i can get it out. :eek:

so it means that only 3 screws will hold my backplate on. do you think this will be a problem? should i put some gasket sealent around the backplate?

any tips or advise??

did i just stuff my 353? :cry::cry:

Maybe try to carefully apply a drop of CA at the end of another screw (not in threading), screw in until it contacts with the broken part
let it some time and hopefully by unscrewing, the piece will come off. Just an idea...:nod:

If the tread is that deep a new screw on the right size should fit on top of it, if it is that deep that even a new screw can not screwed on top of it then use a dremel with a cutting disc to make a sleeve into it so you can use a flathead screwdriver to get it out.

Hate to say it, but if you can't drill the screw out you'll have to buy a new crankcase. Otherwise, you'll have an air leak that can't be resolved by using silicone to seal the backplate.

This happened to me. I have a friend that races with me and works in a machine shop and was able to get it out. The screw was not deep enough to allow another screw nor out enough to dremel it with a disk.

I am not sure what method he used to remove the screw, I know it was just possible to. You might have a chance to take it to a machine shop and they might know what to do.

I also recommend to fill all holes in the crankcase with cloth so no debris enter the bearings.

You can try a 'counterclockwise' drill bit. Don't know if this is the proper english name for it, but basically it is a drill which cuts the other way around.
When it cuts into your screw it grabs it and unwinds it.
Most of the more advanced hardware stores will carry this kind of drillbit.
The best solution is a counter-clockwise tap, but the screw is properly too small for it and it is kind of expensive if you have to buy a set.

But I think you could still run the engine with 3 screws without a problem, I ran an engine with 2 screws in the backplate for a day because the other two were to damaged to use them. The O-ring makes the engine air-tight, the backplate won't buckle or anything because it misses one screw.
You could buy some 'lucky 7' engine sealant to be 100% sure, this has been made especially to use on a assembled engine.

Yes, a counter clockwise, aka left hand drill bit, spun by a drill motor (backward of course)

I suggest-


Heat the crank case up to around 200-220 to expand the aluminum to make the steel screw easier to remove. also use a penetrating lubricant,

Drill into the remaining part of the screw, with fresh new drillbit, apply pressure to drill hopefully the bit will "bite" into the remainder of the screw and back it out.

This can be tricky if the screw has broken off at a weird angle (not very flat) as it may cause the bit to wander and drill into the crankcase threads. Turn the drill motor slowly.


good luck! heat is your friend! :flaming: