Well winter is long gone for me, actually it never started because of the poor weather. *So I decided to dig into the top end of my 74 tnt 340 fan. *WOW what a mess. *I can't believe I had this thing actually running this year. *The owner before me did a hack job with it, so anything I say i had nothing to do with, i'm just trying to fix it.

Forgive me I don't know the name of everything here I just need some advice. *I took the heads off. *You have the spark plug hole, the dome, and then a thick ring around the outside of the dome I think this is what make contact with the gasket. *It looks like someone took the end of a flat head screw driver and started poking into it, HARD. *There are dings and burrs all over. *Can this be fixed or am I better off replacing? *Also, if I were to machine this area, is this what they call machining the head for performance? * On the same piston there are only a few small similar dings on the dome of the piston, can i take some 400 grit paper to this area and remove some carbon and these dings? *As you can see I'm trying to get by as cheap as possible and yet still have a functional sled. *Also, the same cylinder has 2 huge (at least .025" deep) score marks. *Is it cheaper to find a used cylinder or to have a sleeve put in? *Does anyone think the damage was caused from motor failure or human abuse? *I've never seen a motor cause the stuff I saw on the head http://www.snowmobileworld-s2.com/forums/iB_html/non-cgi/emoticons/sly.gif

Could you post a pic of what the head looks like? Where are the marks located ? If it's on the dome and piston, this would be due to some dirt or something comming from the air intake and being knocked between piston and head, it could also have caused the scoring marks. If it's really bad, you might want to machine the dome and you could shave the head but I'm not sure if I would put that much money for a 28 yr old sled. You could bore the cylinder and put oversize pistons if someone still makes them. Check out wiseco and only go in kimpex if you are desperate.

I'll try and pics tomorrow

I no exactly what you mean, i have seen that more than once on thoes old doo's. AC is right, thoes marks are caused by something that got in there, could be the rings, how do they look ? *If you look around you could probably find a used 340 for parts pretty cheap ! i have a 440 fan sitting in the garage but its a bit far for you. It came out of a tnt 79. I have seen guy drop new pistons in leaving the head like that, and still have thoes thing running, They were not fast but Strong. Good luck

I think you guys are right. *It looks like something blew up and put debris up into the head. *That piston is long gone, the person who had it before me put another piston in there. *So i'm going to sand that area off and put her back together. *I was wrong in my first post, that area does not make contact with the gasket, it was full of carbon. *So I see no problem cleaning the burrs off and putting it back together. *

Kind of makes me wonder where all the pieces that did that damage went http://www.snowmobileworld-s2.com/forums/iB_html/non-cgi/emoticons/wow.gif http://www.snowmobileworld-s2.com/forums/iB_html/non-cgi/emoticons/confused.gif??? *Hopefully the exhaust?http://www.snowmobileworld-s2.com/forums/iB_html/non-cgi/emoticons/confused.gif?

Correct me if i'm wrong but the ring where I have all kinds of nicks and burrs is the squish? *I think??