Oil consumption

[BuB400]

I have a 1999 400EX. Quad is all stock and I always keep up on maintance(valve adj.,etc.). Last trip I took after 8 hours of hard riding I used about 8 ounces of oil. I forgot to change the air filter that morning, and by past experience it will use a little oil if it can't breath. Quad does not smoke at all, and does not normally use alot of oil. So my question is,time for a rebuild? How much oil do you guys go through on an average day?

[CJM]

None, I dont use any.

Could be as simple as the valve seals going bad, it will smoke a few puffs on a cold start if they are bad. Or its rings and you will consume alot of oil and smoke badly sooner or later.

If you have a good bit of hours and havent rebuilt it for years then it probably needs rings. Id also have the bore checked for proper size to make sure its not egged or worn out.

it has to be smoking even slightly because the oils getting past the rings somehow or another and being burnt. Otherwise if its not smoking either you didnt add enough when you changed it last or its leaking somewhere.

[BuB400]

No leaks, and I checked oil several times on the trip. Must be time for rings. If I have it apart how hard are valve seals to do?

[CJM]

Check compression first before you do anything. Stock spec is 120psi or so, if you have less than you know for sure its rings.

To do the valve seals is rather easy. You need a valve spring compressor (rocky mtn atv/mc sells one for like 35 bucks) and you compress the springs on the valves, remove the valves and simply replace the little rubber valve seals. While your in there clean off the valves and the head well with a wire wheel and carb cleaner. Then if you want to get fancy lap the valves using a power drill and lapping compound if you want.

[BuB400]

Hey CJM, thanks for the info!

[CJM]

Welcome Bub. Good luck with it!