Hi to all: new member. I signed up to try to get some help from guys that know about polaris atv's. I bought a 91 polaris trail boss 350 for my grandson. brought it home, told him to go ride it for a while, after no more than 10 minutes of easy riding it seazed up. I tore it a part to find the water pump bearings had fell a part and it tore a whole in the 2 engine crank cases, I had the cases welded only to find out that the cases had worped. and the water pump counter balance won't fit all the way like it needs to. I'm having huge trouble trying to find a set of 350 cases.
So here is my questions will a 95 400 exployer xp take the parts that I have bought for my 350, will the crank and water pump counter balance from the 350 work in it. and will it bolt up the same as the 350. looking at pictures which is all I have to work with, they look the same. I no you can swap out cylinders and pistons with 350 to 400 but not sure if I can swap out internal parts as well.
also will a 400 water pump counter balance fit the 350 case I have a really good one I would like to use, if I have to stay with the 350 cases. thanks for any help you might be able to get me.

 

Welcome! The crank shaft and rod are the same on the 350 and 400 along with the the internal parts. Major difference is the larger cylinder bore and piston on the 400 versus the 350. Plus if you found a 400 engine to mount in the 350 frame you would have to use your stator,flywheel,etc because the two ignitions will be a little different. Engine cases do show to have different part numbers though,but don't think they are that different. Never did much swapping around engine parts from a 400 to a 350 or 350 to a 400 engine. OPT

 

okay I found what looks like a good used 1995 400 exployer case, that I can get afforably. as long as it will take my internal parts and bolt up. I can easly use the stator and flywheel from the 350 no problem. one last question. is the water pump counter balance the same for both engines. they look the same. but I'm wondering if they spec out the same. thanks a bunch for your help.

 

Water pump and counter balancer shaft are the same in both models. OPT

 

great info great site as well thanks again.