triumph t100 oil coming out breather tube

[kbass]

I bought a 1979 triumph t100 last year. It ran great. I put it up for the winter, This spring I changed the oil and when started up it spit oil out the breather tube. Where do I look to see what the problem could be?

[L.A.B.]

1979 T100 ??

[Matt]

What oil did you put in it?

[Rex]

No such bike. Is it a typo for 1969 C range, or a 2009 T100?

[kbass]

My error. It's 1970. Castrol 4t motorcycle oil sae 20w-50 recommended by old knowledgeable bike dealer.

[R]

When you changed the oil, did you drain the oil out of the sump, as well as out of the oil tank ?

Lotsa bikes with dry sump oiling, including probably your Triumph,  are famous for the oiling draining down into the sump when standing - and puking out the breather or overflow when subsequently started.

[Bomber]

Even not so old bikes "wet sump", my wifes 2003 Harley Sportster does!

[wetdog]

oil pump ball valves not seated

[Rex]

I bought a 1979 triumph t100 last year. It ran great. I put it up for the winter, This spring I changed the oil and when started up it spit oil out the breather tube. Where do I look to see what the problem could be?

As has been said, possibly you've over-filled it so either drain and refill or go for a run and leave the excess all over the country-side..

Triumphs aren't known for suffering from drain-down  (totally different from wet-sumping, incidentally) but they do spit oil from the breather if the bike has been parked (or had the oil changed when parked) on the side-stand as the oil collects in the pockets around the inlet cam end and affects the breather on start-up.
I doubt there's anything actually wrong with your bike that a quick blast wouldn't sort...

[L.A.B.]

Triumphs aren't known for suffering from drain-down  (totally different from wet-sumping, incidentally) but they do spit oil from the breather if the bike has been parked (or had the oil changed when parked) on the side-stand as the oil collects in the pockets around the inlet cam end and affects the breather on start-up.

But, a 1970 model T100 should have the open drive side bearing and primary case breather.

[Rex]

Good point. I presume then that "breather" in the OP's post refers to the tube going out over the rear mudguard, therefore the spitting is probably down to the oily residues in the breather pipe condensing and collecting in the lowest point, ready to be blown out on start-up?

[Bomber]

http://www.classicmotorcycles.org.uk/technical/technical_wet_sumping.htm

[L.A.B.]

http://www.classicmotorcycles.org.uk/technical/technical_wet_sumping.htm

If that was a reply to Rex's comments about "wet sumping" then he's correct in that what is generally referred to as "wet sumping" these days is actually oil draining from the tank to the sump, or: drain-down.

Wet sumping in the original true sense of the term refers to the inablity of the scavenge system to return the oil from the sump back to the oil tank while the engine is running. 

[Bomber]

"Wet sumping in the original true sense of the term refers to the inablity of the scavenge system to return the oil from the sump back to the oil tank while the engine is running.  "

These days, I would have called that a knackered oil pump or a blockage 

[Rex]

Don't know about "these days" but Triumphs (with thier double-plunger oil pumps) can suffer from wet-sumping for a variety of reasons but unlike gear oil pumps as used by BSA, Norton etc etc) they don't (as a rule) suffer drain-down; it's the design of the oil pump.
They also don't tend to ever wear out ("knacker") the oil pump either, so were you to rush out and buy a new pump, you'd likely waste your money on an unnecessary purchase and not fix the original problem. But that's "these days" I suppose....