A couple of years ago I acquired my 624 with a bad carb one that could not be fixed. Seemed impossible to find one. Didnt know about this forum till recently. Being a small engine tech I came across a briggs 6 horse engine at work that the carb looked like it would fit. And it did. The only issue was getting the intake butterfly to go in the reverse direction. Using the upper part of a throttle shaft from another carb and a small screw and nut was perfect. The gov linkage lined right up and worked perfect. Runs incredibly smooth. Now did I get lucky or what? Does anyone find anything wrong with doing this? And believe it or not the carb I used can be purchased on Ebay for $7. I bought one for a back up but ended up putting it on anyway. The carb intake box I had to do a little cutting for the choke lever and am still goofing around with the best cover. I have attached pictures of things. Live in Wisconsin and need to sell the machine so if anyone is interested let me know.
Can you link the carburetor you used?
Best price for yamaha replacement was about $270 with shipping (I think) and I'm still waiting for my replacement. I have a couple $20 amazon models in my cart, and was gonna buy one just to take a shot. Nobody lists a cheap alternative that works, anywhere..
6 horsepower Wisconsin Robin carburetor Almost an exact fit except to thread holes in carburetor for air Box you must use nut and bolt Wisconsin Robin is made by Fuji heavy industries which is the same identical engine as the Yamaha go figure About $50