my brother in law had one of these 600 grizzes. he had loads of problems with it.take the side plastic covers off.they just run too hot.another thing to check is,the tubes coming off the bottom of the carbs.they get clogged with mudd and wont let the float bowl fill back up.the tubes run down between the frame and swing arm.take them off and blow thru them. make sure they are clear.he also had a problem with the wiring harness,but you said your is new.some coneections melted under the front plastic by the steering stem.also,your valves,if adjusted too tight,as the motor gets hot,the stem of the valve expands.this will in turn push the valves some what off the seats,cuasing a loss of seal at the valve seats until they cool back down.if the motor ticks alot,then it is possible that the timing chain is worn and someone adjusted the valves too tight trying to get rid of the ticking noise.hope this stuff helps.i would check those tubes on the bottom of the carb first.very common problem.
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