Carb Question for xp150

[hunter85]

I have a 87 xp150 with carbs from an 85 xp150. I was having issues with starting and once it started it would fall on its face when going on plane so when I removed the carbs to clean I found that the timing advance bushings where broken so I replaced then with the ones from my junk 85 model but I believe I may have switched my top and bottom carbs around but when doing a parts search it shows that I have a top and two middle carbs the part numbers a 394741, 394742, 394742 in that order. My question is what is the defferance between the 41 and 42 carb. Any help and advice would be greatly appreciated!
Thanks
Nic

 

[KCJ]

I have both an 81/150 and an 85/175, with the same setup. Though I am not 100% sure, the most obvious difference is the linkage plate on the strbd side of the middle carb. I believe that I have read that the jetting might be different from top to bottom but I would have to verify that. The 85 was put up wet and needs carbs cleaned, and the 81 had carbs rebuilt last year by previous owner (he was and idiot!) won't idle below 1500 rpm and smokes like hell, I think it might have other issues too. I'm just waiting for spring to get started.