well heres the story, i recently pick up a 2002 400ex for $900 with title from the original owner, the bike had a 416 kit with aftermarket rod with a whitebros pipe, k&n filter and ported head and was jetted, well it smoked real bad and sounded like it had marbles in the topend, well tore it down and with further inspection i found that the cam had ate the head it put alot of scoring where the cam rode and the oil rings were shot on the piston so i pitched all of that. Well i got another engine that was apart with the bike it had come with a hot cam #51 the jug was freshly bored and honed to .25 over or a 86mm and the head was ported, well i bought a piston and rings for that 86mm jug and a top end gasket kit with cam bearings and valve seals, well after all was assembled i fired it up and she smokes and bad! it clears up a little as the bike get hot but it uses oil and it concerns me. Did i miss somthing? i just want a reliable bike just to haul logs with and trail ride but this 400's not looking so good right now.

also ive got another question about a noise, the noise is that the top end sounds real mechanical compared to my buddys 07, are the hot cams #51 make the bike sound more mechanical than stock.


Any input is greatly appreciated.

thanks

 

Did you have someone with a micrometer measure the cylinder and piston? That's the only way to tell if the clearance is correct, and the cylinder isn't tapered or out of round. Valve guides would be another possible source of smoke.

I would expect (but don't have any direct experience) that a high performance cam might make a bit more noise, but I wouldn't expect a lot.

 

I had the 40 over kit with hot cam in my 02 400ex- the only reason I put the 40 kit in was because I had to pull the top end off due to blown rings (lots of smoke)
I don't think it was a good idea to pull parts from one motor and use them in the other- and you should've had both cylinders mic'ed before buying any pistons- Now it sounds like a frankenstein motor
my bike was no more noisier with the hot cam then it was with the stock cam.

are you sure you stacked the piston rings properly?

 

Both were micd and. Checked before use same with all parts

 

Everything was done by the book. rings and all

 

The biggest mistake I see when I see posts like this are:

#1. Rings in upside down.
#2. New valve guide seals were put in but not new guides or valves.

Oil can really come from the piston rings or or the valves.

 

the rings go? numbers facing up with the shiny rimed ring on top correct?

im going to look into the valve guides this weekend.

 

I know you said "by the book" - but not stacking the rings properly on the piston will allow oil blow-by.

 

One thing I question is you said you bought the piston after the jug was already bored. My machine shop will not bore a block until he has the piston(s) in his hand. There is just too much room for error.

One or two thou can make a BIG difference in oil control.

Every ring I have put on the dimple goes up. As far as the ring order I have no idea on this engine.

 

Did you check the ring gap, or the valve guides for were?
Is there a chance that you used standard rings buy mistake?