1975 hondaXL 250 Rattles and smokes

[TAK]

I have a 1975 Honda xl 250 and it rattles and produces greyish white smoke that wont go away, I have been been told that the rattling is normal, but I don't think so. is it my valves? or is there something else?

[Johnj]

Sounds like you need to rebuild the engine.

[GS_in_CO]

Did you buy it in this condition?
Is this a resurrection after sitting for 20 years?
Was it parked because it was doing this?
Did you find it in a junk heap?
Did you put oil in the cylinders when you prepared to start it up?
Did somebody before you do that?
Did you put fresh fuel in it? Could it be old fuel that someone might have mixed oil into thinking it was a 2-stroke?

Rattling could be most anything. Get a service manual.
Start with looking into how the cam chain is tensioned.
Then see how to adjust the valves.
Then see if you can check compression.

BTW- oil smoke is blue, unburned fuel (too rich mixture) is black, gray smoke is usually coolant but in your case it's air cooled so....... you probably should check the smoke color again. Well, condensation of exhaust into cold air is white but could look gray. So if it's cold where you are and the engine is cold you might get a steam cloud.

If you have the time to work thru the issues this will be a good learning experience. (believe it or not)

[TAK]

I have corrected the valves and still have the same problem. the smoke is a greyish white, and it will go away after riding it for a while, but when I stop the smoke starts to slowly build back up when the RPMs return to an idle.

[GS_in_CO]

I have corrected the valves and still have the same problem. the smoke is a greyish white, and it will go away after riding it for a while, but when I stop the smoke starts to slowly build back up when the RPMs return to an idle.

Possibly valve guides/valve stem seals.
High vacuum at idle pulls oil thru the worn/hard seals.
(Or it's a Ford V8 and the head is badly sludged.....)

Smoke is probably blue if you get the light just right.

Or it's gas that someone thought needed some oil in it because they thought the bike is a 2 stroke.