ak-guy
Senior Member
I have a small Yanmar with a dual foot alternator. I get some belt dust and the belt is difficult to get tight because of play in the pivot bolt. Also the 8mm bolt has sleeves to bring the size to 10mm or 3/8" for the holes in the alternator feet. This also causes some slop. This quote from another forum describes the situation.
"One of the biggest issues on Yanmars is that the M8 pivot bolt fits VERY sloppily in the engine mount hole and the alternator mount holes. If you are brave you can drill the engine mount to accept a larger bolt that fits more snugly and is not a "sloppy" fit...."
So if I wanted to drill out that 8mm pivot bolt hole to 3/8" what would be the best method? The casting is aluminum I think. My fear is that rather than drilling a perfect hole the bit would wander slightly and result in worse alignment. Perhaps a gradual increase in bit size?
"One of the biggest issues on Yanmars is that the M8 pivot bolt fits VERY sloppily in the engine mount hole and the alternator mount holes. If you are brave you can drill the engine mount to accept a larger bolt that fits more snugly and is not a "sloppy" fit...."
So if I wanted to drill out that 8mm pivot bolt hole to 3/8" what would be the best method? The casting is aluminum I think. My fear is that rather than drilling a perfect hole the bit would wander slightly and result in worse alignment. Perhaps a gradual increase in bit size?