I've seen a lot of time's people don't torque the bolts to spec or they over tighten and stripped threads if the machine has been tore into more than four to five times the stud bolts need to be replaced. Tighten and loosen over and over can pull threads causing them to back off from vibration and heat. Hope this isn't your case maybe they just didn't torque it down right. You can search online and find out what the torque specs are.

 

How will i know If the stud bolts need to be replaced ? And if they need to be replaced , is it hard to replace them? And what should I replace them with? Also how do u replace them? Thanks for all the help

 

33 foot pounds is the torque that I found they need to be torqued to if you cannot torque them down. Meaning they stripped use two of the nuts jamming them together turn the bottom nut you use to screw the stud bolt out I've had some luck using vice grips. But jamming the nuts is the best way to do it

 

You should be able to purchase the stud bolts on eBay and also make sure the washers are on all the nuts if I'm not mistaken they should all have a flat washer if the washer is missing they may torque down but it could be because you ran out of threads on the stud the washer is a spacer and is a certain thickness. Hope you getter going.

 

Got the ex tore all the way down to the cylinder.. haven't took the cylinder off yet.. all the bolts seemed good , not stripped.. head gasket was just fine... but there was oil on the top of my piston, which leads me to believe I need new piston rings. Any advice would be greatly appreciated

 

And the guy lied he said it was a 416.. and on the piston it says 85.47 which is a 402 I think.

 

Be sure you mic the cylinder with a caliper I'd recommend you order new top end gasket set..and the right rings and torque the cylinder nuts in a criss cross pattern go to 18 lbs first on all 4 then in the same pattern 33 lbs also be sure that you have all the washers on them too.. good luck hope I've helped you out I traded my 01 400 ex for a 06 outlaw 500 but still missing the 400ex

 

If you can afford it I'd order the hot cam stage 2 and a jet kit and a Rev box and hmf exhaust you can get it the color of your bike it made my 400EX run around 80 miles per hour if nothing else by a part here and there it will really wake it up oh almost forgot 15 tooth front sprocket and I believe 36 tooth in rear you can feel the difference

 

Thanks for all the advice.. how do I know what piston rings to order? It is a 85.47 piston.

 

It's a namura piston go to eBay type 400ex 85.47 piston rings it will pop-up I just looked at them $16.00 roughly me myself I haven't really liked namura brand they seemed loose fitting.. I'd recommend that you get a weisco piston kit that is 85.47 if there is no ring Groove in your cylinder and cylinder is good and slick