Holy Crap!!!!!

my 400ex is a 1999 and it has never been rebuilt. its stock except a t-4 slip on and jet kit. when i start it when it is cold it smokes. some black and some white. what does this mean?

i think it means your rings are worn and oil gets by them till the motor heats up and causes expantion..time for a 416 kit

[Dave400ex]

Yeah, just get a JE 416 Piston and a XR400 Cam from Marcum`s ATV. You can have a New Rebuilt Motor for around $300. Plus you will have More Power, which is always good.

Yup your rings craped out.

[Pro400EXC]

My 400ex is a 2001 with a T-4 slip on and a 155main jet. Mine smokes too,but I think it cause it's tooo rich,but my 400ex smoked since new. Those XR mills are known to smoke.

Heck my 400ex is a 1yr only while my buddies is 4months, and mine smokes, and we both have the same pipoe and jets,but my 400ex feels more powerful.!

what is the best 416 kit? how much and what all does it come with and what else needs to be done to the motor. thank you

call marcums the site sponsor. he'll send everything needed to you for 148 dollars. only thing is it takes them about 2 weeks to bore your cylinder and sen it back

[Dave400ex]

Yeah call Marcum`s. Since you are getting a 416 Piston Kit I would just save and buy a XR400 Cam too. I think the whole 416 Kit from Marcum`s is around $300. That`s what I would do.

does just the piston come with the 416 kit from marcums, or do you get anything else with it? is it ok to run the 416 piston and cam with no other motor mods(stronger connecting rod, etc)? for 300 bucks i guess you cant go wrong. also, does anyone know what kind of compression you'd be running with that piston? im hoping to keep it under 11:1 so i can run on pump gas. thanks

Mike

[Dave400ex]

The Kit includes a 10:8:1 (I think) JE 416 Piston, XR400 Cam, Viton Valve Seals, and maybe more. I`m not sure. This Kit is fine to use with the Stock Rod and Stuff. You can run Pump Gas with this Kit too. If you want to know anymore on the Kit, ask Rico. He has the Kit from Marcum`s.

[big-guy]

Black smoke is unburned fuel, the white is water vapor.
You might be a hair rich, but if it stops once it warms up, I wouldn't worry about it.
Throwing money at a "problem" won't always solve it.
If it's using oil, and giving off blue smoke, chances are the rings and cylinder are worn, and a rebuild may be in order. I don't think that's the case here though.

thanks WarriorMan :D