Iwould pull head it an easy to remove inspect values and you also can inspect cylinder and piston some

 

Yea I was afraid of that. Sounds like possibly complete tear down maybe. I’ll take head off and inspect. Going that far I may as well buy new timing chain and tensioner and put on it seeings how the head is off I can get the tensioner out

 

Not sure why you claim to be able to get at the chain tensioner, on the 450 it is inside the clutch housing. On the 400 it is outside, hidden by the cylinder and head fins. You don't need to touch the bottom end of the engine to take head and cylinder off, nor any need to remove it from frame, so going for a new timing chain is pointless unless you can hear it slapping away once you get the engine running. Only exception to that is if the piston has broken up, I'm rebuilding a 400 King Quad at the moment, where the piston skirt had gone, amazingly still ran and didn't smoke, though made a terrible racket. I had to remove engine and split cases to get the broken bits of piston out.

 

merryman...... im not an expert on any of this... all that i have learned is from reading other posts... i seen where someone mentioned taking head off to get tensioner out to replace.. the timing chain and tensioner replacement was from where is seen a possible jump time due to stretched out chain from the skirts cracking and/or breaking..... so might as well replace tensioner as well if im gonna do the chain right?.... im learning as i go. this 4wheeler was gaven to me. i dont mind putting a little money in it (which original post will show what ive put in alrdy) to get it going and hopefully lasting me for while to use when im hunting.

 

Update:::: Papa Hogg Scoot... so ive pulled the head and the cylinder... i found the problem.. one side of the piston had some really hard wear to it and i believe the rings were stuck in place and wouldnt move. the cylinder wall had alot of wear to it as well. Looks like this bike was possibly run really low on oil from the damage to piston and cylinder. With that.. i tore everything down... wrist pin gave me a fight. alot of heat and 3 different bolts(first 2 end of snapping) it finally got it out of the rod enough to get piston off. The rod journal looks nice and shiny.. no marks are scrapes. So now to order top end rebuilt kit and start getting this thing back together. I am gonna replace the valve seals(which ill have to order engine gasket kit for those) while the head is of because of alot of build up on bottom side of head. Thx for all the help on my problem. ill update once again once it back together with the results.

 

Love to hear from you after the build and Thanks for the update

 

If the pin was tight coming out it usually does score the con rod eye, try the new pin through before fitting it to piston. If it doesn't go through, I clean up the eye as best I can (I have a reamer but that rod is hard) and finish off with the old pin covered in metal polish. Slide it in and out and round until the new pin will just slide through. Clean all traces of polish off before fitting piston.

 

Merryman.. no doubt.. I plan on checking the pin in the rod before I do anything. By feel and looks.. it seems ok to me but I’ll fit the new pin before hand to make sure. I’m not doing this again