Have a 400EX that ran without burning any oil and didn't smoke a lick until about a month ago when we put in a new timing chain and adjusted the valves. Also put on an exhaust and header about 2 weeks before we put on the chain.

It runs fine but, now it has a light colored smoke shoot out when under a load. There is also a lot of black sludge buildup inside the new exhaust. What would cause this problem?

Haven't yet ran compression test.

We changed oil types from Bel-Ray to Honda brand would this cause any issues related or not?

 

try running benol only 50/1 and you may have to get piston and rings
benol (beanoil) is more money but it will run forever...

 

blackness inside a new exhaust is normal but not sludge...

 

I have a 400 ex that smoked ( when I bought it) and had no power until I changed the timing chain and bored it out ...now I can't even get it to start... any suggestions...we have tried everyhting

 

since you just changed the oil, are you sure you didnt over fill it?? Also check to see if theres anything in the airbox, like oil from the air filter, etc.. if not, you probably have bad piston rings, thats what usually causes a smoking under load. smoking on deceleration would be valve seals/valve guides.

 

Ah, so valve seals smoke on deceleration and rings on acceleration. Didn't know that. Thanks quicksilver. Only thing is that it was rebuilt not even a year ago.

No oil in airbox and always very careful not to overfill.

rononahonda: You probably have the timing off. Go back and line up your marks and try it again.

 

Check your compression and do a leak down test. That will tell you about the rings....