I know it's a 2stroke, but this is definitely an abnormal amount of smoke coming out thru the exhaust. I ran it hot on our last trip because the heat sensor that turns the fan out apparently went out at some point that day. It boiled over and steamed out thru the overflow tank. I let it cool and filled it back with water and bled the bolt in the head. While it cooled I strait wired the fan so it would make it the rest of the weekend. After all of this it ran fine for the rest of our trip. I went out to start it last weekend and noticed a bit of odd smelling smoke bellowing from the back, bad enough that it looked like a leaf fire. And today I hopped on for a short ride thru the neighborhood and fogged the whole place for mosquitoes. Compression is still great but my water was a little low when I got home. Any ideas on where to start? I'm thinking head gasket but will entertain most other ideas as well!

 

Sounds like a leaking head gasket,plus I'd have the head and cylinder checked for any warping.Plus if you do this might as well check out the piston for any scoring,etc.Guess you kinda see where I'm heading. I wouldn't just throw another head gasket on it since it got hot,but that's just me.

 

That's where I was leaning as well. I've already ordered a set of cyl/head gaskets and hopefully that purdy weisco piston still measures fine as well as the cylinder Thanks again OPT!

 

Well, it wasn't a head gasket leak. I drained the crankcase and about a cup of grey thick milky goodness came out of it after I tipped the 4w up on it's nose. So, I guess I'm a third case gasket and a water pump housing gasket away from being good to go now. Could it be anything else? That's the only other thing I can think of unless there's some sort of seal in there somewhere I can't remember

 

Bad inner crank case seal behind the stator would be the only way to allow c/b fluid and coolant to get by other than a base or head gasket failure.If you're getting coolant in the crank case it's got to be coming from one of these three. Item 24. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

In replacing that seal, will I need to replace the 3rd case gasket(#25) or can I get to it without removing the outer case(#28)?

 

Gotta remove the third case to get to the crank seal because of the big third case bearing #26. If you can save the gasket,then ok. May or may not be the problem as I'd look for any cracks in the cylinder or engine case also. Seal is the only thing I can think of if crank is full of milky coolant and you said the head and base gasket wasn't the problem.

 

I'll go ahead and get both gaskets and the seal. I've been looking thru some other stuff in the web and some other microfiche, where would coolant go if one of the seals behind the water pump went bad? I guess I'll know more either tomorrow or tuesday when I open the side and start digging, I'm just trying to make sure I have every possible culprit known to me so I know where and what to thoroughly inspect as I take parts off.

 

If water pumps seals leak,the coolant would go into the counter balancer cavity and contaminate the 75-100 ccs of oil. It would usually pump out the c/b vent tube if leaking is excessive. That's how most people realize their water pump seals are bad. For this coolant to get into the crank case it has to get by the big bearing in the 3rd case and through the crank case inner seal which is kinda hard to do.That's why I said to double check the cylinder and head themselves for any cracks along with any burnt spots on the head gasket or for any obvious base gaskets leaks. Plus not a bad idea to have the head and cylinder checked for any warping since you have it apart.

 

I don't have access to the machining and testing equipment I used to, but I checked the head and top of the cylinder with a good straightedge and tissue paper and both seemed to be very flat. I had an odd idea cross my mind as I'm typing this, is there any way for the cylinder sleeve to come loose from the jug? It's just an idea, I haven't ever heard of it but I'm sure it's happened to someone at some point. Otherwise, I'll be opening up the c/b side tomorrow evening when I get home and report back here.