I bought a 1999 Sport 400 (basically a 4x2 Scrambler), non running, no compression to speak of. I rebuilt the top end by honing, new piston, new rings, new gasket set. I filled it with coolant and after a few minutes of checking everything over for leaks before firing it up for the first time (I had to remove and re-install the gas tank too), I noticed coolant coming out of the stud on top of the head. So I figured I probably didn't clean something up good. Removed the head, cleaned off everything again, put the head back on (double checked that the "UP" was up on the gasket) and filled it with coolant again. This time no leaks. Cool. Or so I thought. I turned it over and it fired right up (grins), backed it out of the garage and rode it around the yard to give it a little test. Stopped and looked it over and I noticed that the exhaust was burning coolant and coolant was coming out of the head studs again.

What's goin on?

Bad head gasket? (just bought it new)

Bad head? (a friend has one laying around that he said I could try)

Bad jug? (god, I hope not)


Tony

 

someone in the past over tightened the head ,causing the stud/studs to pull up slightly and create a high spot around them that the gasket cant seal letting coolant into the jug ...maybe???
or the head is warped ?? , are you using a polaris OEM head gasket?

 

Ok, so if I overtightened the studs, what's the solution? This could be the issue, as I don't have a torque wrench and snugged them up. Do I just take off the nuts and re-tighten them to the right torque?


Tony

 

IF that is the problem,if. you need to remove the studs and have the top of the jug trued
send it to ritter cycle racing to "take a little off the top" send the head too or i have heard of people using a mirror with some 400 wet and working on it themselves . i chose the ritter option for the one i had done

 

I'm gonna throw that extra head on tomorrow and see what happens. If it still leaks I'll pull the jug and take it to the race engine builder down the road. This guy near me used to build all the factory engines for the Honda national moto x team and knows his stuff.

Tony

 

Anyone know the torque specs for the studs on the 400 head?

 

18-20 ft lbs

 

Which is about the twist of a wrist.