| Without the rest of the numbers,, It's hard to tell.. Did you try a 5/16??? It wont be metric because it's a techumseh... Did you try a coarse thread bolt in it?? Has it been sitting or used as an application where the bolt wasn't used... Maybe you just have to chase the threads to clean them up...Clean them up with a spray type cleaner & blow them out with compressed air & try to get a pitch gauge in there.. I think you're right,,but lets make sure first... Roger |