Author Topic: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.  (Read 992 times)

Offline stevestriumph

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Well it's on to a different bike. The previous issue regarding the 1969 T100 was resolved when I found a piece of sludge sitting in the bottom of the crankcase drain plug. It was large enough to be drawn up and block off the intake scavenge return tube, causing the crankcase to fill up and blow out the breather. That was a first for me!
Now I have a similar problem but with a fresh rebuilt motor on a 1969 Triumph T120 Bonneville. Motor was completely gone through by a friend, (very qualified), who has passed on. My job was to get it running and sell it for his wife. Problem is oil is coming out the crankcase breather. I assumed "wet sumping" but did not have excess oil in crankcase. I pulled the top end to check rings and all was good. I re-honed and installed a set of rings and installed a new oil pump. Compression is good, I have good oil pressure and good return to the tank. I have put almost 50 miles on the bike. It runs great but continues to push oil out the breather. I have re-checked the sump and it's not over filling. Oil tank breather is clear as well. I am at a loss for what to do. Any thoughts? Steve

Offline Rex

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #1 on: October 15, 2018, 10:16:23 AM »
How much oil is being pushed out?  A smear? Continual stream? Put some miles on it and see if the problem remains. 50 is nothing.

A new oil pump though? Bit of an expensive suck-it-and-see approach?
« Last Edit: October 15, 2018, 10:19:23 AM by Rex »

Offline iansoady

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #2 on: October 15, 2018, 11:03:26 AM »
I'm not familiar with the model but does it perhaps have a timed breather?
Ian
1952 Norton ES2
1982 Moto Guzzi V50

Offline mini-me

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #3 on: October 15, 2018, 11:28:21 AM »
Breather on end of camshaft has not been assembled properly, or oil pump is not returning to tank.
the latter problem is more easily resolved, the former is an engine strip.

check pump and return first.

Offline Oggers

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #4 on: October 15, 2018, 11:46:58 AM »
50 miles is nothing to allow the new rings to seat properly. Drain the sump again, and as aforesaid, put some miles on it.

Another possiblity is the return vv in the oil pump is blocked, or the return line to the tank is kinked or blocked. Thus the pump delivers more than it can scavenge, leaving the residue in the sump and causing the breather issues seen.     

Offline iansoady

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #5 on: October 15, 2018, 12:32:07 PM »
I'm not familiar with the model but does it perhaps have a timed breather?

Yes it does:

"Retained behind  the  inlet camshaft  bush  is  the breather  valve  porting  disc, which  is  located  by means  of  a peg.  When  renewing  the  bush ensure that the disc  is  located correctly on the peg."

From the official Triumph manual.

Obviously I don't have enough to do today......
Ian
1952 Norton ES2
1982 Moto Guzzi V50

Offline TGR90B

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #6 on: October 15, 2018, 12:58:27 PM »
Just keep viewing the sites Ian. There's enough on most of them for a couple of psychiatric seminars.
Getting grumpy.

Offline iansoady

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #7 on: October 15, 2018, 02:27:01 PM »
Yes I've stopped contributing to ikba as it's descending into hysteria.
Ian
1952 Norton ES2
1982 Moto Guzzi V50

Offline stevestriumph

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #8 on: October 15, 2018, 04:02:39 PM »
Thanks one and all for the input. As stated, there is good return to the tank. Amount of oil coming out of breather is minimal but annoying. When sitting at idle it leaves a very small puddle. As for cam shaft breather, I checked the spring back on the cam when I had the cylinders off and it looked good. I guess I will ride it some more, but I have an interested party and I don't want to sell it like this. Steve

Offline Rex

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #9 on: October 15, 2018, 09:18:43 PM »
Ah... and would this idling be on the side stand? Grandma's eggs etc, but do you realise that on the side stand when idling oil collects in the inlet camshaft well at the breather end, and is subsequently pushed out of the engine via the timed breather?

Offline Rex

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #10 on: October 15, 2018, 09:35:52 PM »
Yes I've stopped contributing to ikba as it's descending into hysteria.


Shame...you're missing some world-class willy-waving over who has the most exotic holidays at the moment. I think it reached it's nadir some weeks back when some tw*t posted pics of his worn-out bike gloves... ::)

Offline iansoady

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #11 on: October 16, 2018, 10:01:30 AM »
I do have a look every now and then just on the off chance someone has posted something interesting (and hasn't had 30 inane responses).
Ian
1952 Norton ES2
1982 Moto Guzzi V50

Offline stevestriumph

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Re: 1969 Triumph T120 Fresh motor and oil coming out the crankcase breather.
« Reply #12 on: October 16, 2018, 04:36:40 PM »
Bike will leak on the center stand as well.