A helicoil will work fine if the instalation is done correctly. You will need to come up with a drill and tap guide to keep the insert perpendicular to the base surface. You will of coarse need to make sure no chips are allowed to fall into the crankcase. Clean the hole with carb spray and apply a little green loctite or sleeve retainer to the outside of the helicoil. You will need a small needlnose plyers to hold and break the install tang at the bottom of the coil. Studs are designed to have an interference fit, so give the loctite time to set up before threading the stud in, making sure the insert does not thread in. Its a pain of a job, but if you take your time and do it right it will work fine.