I recently bought a 1991 xt600k. i have driven it about 200 miles.

the last 60 miles it has had a lot of smoke from cold start. its only when i start it cold. it smokes only for 2-300 meters then stops and behaves normal

i have had to refill about half a litre of oil on these 200 miles.

what can this be? do i have to do anything whith it or just check the oil ofthen?

My 1VJ (40,000km) intermittently behaves in exactly the same way: a cloud of oily blue smoke on startup, that goes away after a minute or less. There is negligible oil consumption.

I personally think it's wet sumping ie although it's a dry sump bike with a separate oil tank, sometimes extra oil runs into the bottom of the engine, so that when I start it up again, there is extra oil down there that is forced past the piston rings and causes the smoke. This only happens until the oil pump has had time to scavenge out the excess.

In my experience this is very common on old Brit bikes with worn oil pumps, but I wasn't aware of it on XTs (the admittedly new XT500 I owned in the early 80s never did it). Guessing again, perhaps it only happens when the oil pump comes to rest in a certain position?

One other cause I can think of is worn valve guides and valve guide oil seals. Perhaps I should change these (easy job) to eliminate that possibility.

Last option is oil getting into the air box via the breather, pooling somewhere when the bike isn't running, then being sucked through the carb on startup.

Basically oil is getting into the bore, and assuming the head/base gasket isn't blown internally (which would cause smoke all the time) that can only be one of those routes: up the bore, through the valve guides, or through the carb with the fuel.

Any other ideas?

Found this pic of the beasty behaving badly after an overnight bivvy in Morocco (near Fezzou) last year - is this what you get?

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yep, the picture illustrates it well. but it only lasts for 3-400 meters.

i have to reply on the first answer when im back from work, thanks for the pointers

this afternoon i noticed that one of the bolts that hold the foot peg on the brake side was broken. it was easy to see that both had been welded on earlier. do these ofthen brake?

now i have to get this welded. what type of weld should i do? i will ask a garage to do it. see picture

Bildr.no

The bike will do that if you overfill it with oil, one could hope it would be that simple. It doesnt take many 100ml to make the bike do that.

It can be hard to "read" the oillevel on theese bikes. You need to tun it good and warm, and then check oillevel almost instantly after shut the bike down.

Valve stem oil seals. When its parked up overnight a tiny bit of oil leaks past them and into the combustion chamber. Smokes for a moment when its started as it burns it off. My 86 bike did it until I changed them.
Although oil consumption was virtually nothing. It doesnt take much oil to make a bit of smoke.If you've used half a litre in 200 miles, sounds like you have another problem to go with it.

Often break? > not that I've ever heard

Difficult to tell with the paint on but it looks like those bolts may have been silver soldered in or brazed in judging from the brake lever as well. Hopefully it's silver solder. If you heat it up with MAP gas and the solder / braze melts allowing you to retrieve the bolts you will see if it's the threads that have gone in the frame. If they havent no welding should be neccessary at all. If they have I'd be tempted to use a bolt /nut combo thrather than welding.

oh, i thougt that they were welded in the frame origianally. so they are screwed in? then i can try to screw them out with help from some heat.?

if they have been brazed or silver soldered in you need to undo that first. Note the metal will need to be cherry red before it gives. However before doing that do check that it is a braze or solder job first and not a weld (or indeed not a stud. I only assume its been welded because you said it was). Clean off all the paint first. Brazing will have a copper/brass look to it and silver solder very much lighter v-light gold/silver and look like your photo of the repair on the brake leaver dogleg.