ORIGINAL: Quikturn
Hobbsy, thanks for the info! I have a Saito 91 that turned out to be not such a good deal. I was going to clean it up before I used it and came across discrepancies. One of them being a stripped out screw on the lower left rear cover plate. I believe those are 3mm screws. The cylinder hold down screws are slightly larger at 3.5mm so I thought I would re-tap the stripped out screw for a 3.5mm one. Initially, I wanted to modify a 3.5mm screw into a tap using a cutting wheel but a purpose made tap would be better. I would hate to mess up a crankcase with something not up to the job. I just wanted to be sure which tap I need to order.
Joe
The stock rear cover screws do not go all the way to the bottom of the hole in the case. (at least not on te FA150)
There may be enough thread left to use a longer screw. I think I used the length screw that was used in the FA150 cam housing.
Anyway, check the depth of the hole against the length of the OEM rear cover screw. If there is enough depth, try a srew that is 1mm longer or better yet instal a stud in the hole. No dangerv of bottoming out & breaking off a screw W/a stud.
A "bottom tap" may also get you enough additional threads to get a better hold.