Definitely a bit cold blooded. If it doesn’t sound right I’ll turn the key off, give it a sec and then it’s much less grumbly. Asked my salesman about the spark arrestor and he suggested swapping it with a regular flapper. Seems boneheaded to have one on there to allow water into the muffler and increase back pressure!? If your locale allows it that is.Just got one on a 18xp, runs great but first cold start after a foggy night it grumbles. It skips at 350rpm for 5 seconds, then catches. Going to put a bucket over the spark arrestor at night to see if that helps. 30hrs on machine, plenty of power though, very pleased.