Recently my 670 pilot started to run lean and would occasionally hang and not immediately come back down to idle. I suspected the intake to be cracked again, and sure enough i was right. They all end up cracking in the same spot, and i cant figure out what exactly is causing it. I believe i have posted here before about this same issue, but this time i wanted it to have its own thread. Ive got 2 theorys.
1. The weight of the carburetors is too much sitting on top of this thin intake manifold causing the cracks. When this intake was used in the SeaDoo, they had a brace that ran from the top of the carburetors to the head. I have tried to copy this on my setup using a bent piece of aluminum that bolts to the top of the carbs, and uses longer studs on the thermostat housing to attach to the head. I thought this solved my issue since it worked great for quite a while, so maybe the weight is not the issue?
2. The 670
Engine in a buggy has a greater amount of Engine harmonics that are rattling the aluminum intake apart. Ive never road a JetSki, but i assume the water makes a fairly good vibration damper?
Since this is not my first time breaking one of these, its one of the spare parts i always keep on the shelf so i wont have much downtime, but i would like to try and remedy this issue so it does not happen again. Ive been thinking of filling the upper center cavity (top in 3rd picture) with an epoxy or JB weld to try and hold it all together.
What are your thoughts? Am i overlooking something? Im taking some time to rewire some things and build an input shaft support bearing for my gearbox, so i have a little time before i will be bolting the Engine back in the frame.