T140V Low Oil Pressure

[scottholl]

Hi everyone

So followed Rudie recommendation and rebuilt the engine. One of the conrod bolts was coming loose. At the time I got new bolts but used the old nuts torqued to spec.
So I got new conrod bolts and nuts. No signs of damage on the journals rechecked with a caliper and placed new big end bearings which weren't replaced last time.
Oil pressure is back up and seems alright for now.
thank you all for the help!
Now I probably start another post on the carbs which I am struggling at the moment

Hi Why would a loosing conrod bolt(s) cause the oil pressure reduction?

 

[Rudie]

Why would a loosing conrod bolt(s) cause the oil pressure reduction?

Loose conrod bolts allows greater big end clearance, reducing the restriction that causes the oil pressure.

Triumph T120/140 engines don't usually have high engine pressure and you can tell by watching the oil return line that comes up from the engine back into the engine oil reservoir. Steady stream is a good sign, sputtering oil return tells you the oil pump needs to be reseated and the crank sludge trap needs servicing.

This is wrong.

All oil pumps - including the two types fitted to Triumph engines - have a greater scavenge than feed capacity. In a dry sump system (oil reservoir separate from the engine), the greater scavenge capacity is essential to ensure oil never collects in the bottom of the crankcases.

Because the scavenge side of the pump has a greater capacity than the feed side, the scavenge side will sometimes suck vapour from the crankcase, the variation of oil and vapour appearing in the reservoir - "sputtering" - is absolutely correct and normal.

Dry sump engine, steady stream of oil returning to the reservoir is normal when the engine is first started, because oil has drained within the engine after it was last stopped. If the engine had been started previously only recently, the "steady stream" should become "sputtering" within a few seconds.

If the engine has not been started previously for some time, before starting, the oil level in the reservoir should be checked. If it is very low, it should not be topped-up automatically, the oil from the reservoir can have drained into the bottom of the crankcase. If this oil is not drained from the crankcase before starting the engine, the "steady stream" can continue for longer before become "sputtering". However, "steady stream" never becoming "sputtering" is a problem.

If the oil return to the reservoir is "sputtering", almost nothing can be deduced about the inside of the engine:-

. if the sludge trap is empty, oil will reappear in the reservoir as normal "sputtering";

. if the sludge trap is almost completely blocked but some oil can get through, it will reappear in the reservoir as normal "sputtering";

. if the sludge trap is completely blocked, the oil pressure relief valve will divert the 'feed' oil straight into the sump, it will reappear in the reservoir as normal "sputtering".

use only 20/50W petroleum oil and not synthetic

Nothing wrong with synthetic ime. Particularly its high temperature stability compared to normal dead dinosaur juice will be useful to o.p. @Migsan and other owners riding in high ambient temperatures.

 

[grandpaul]

Working strictly from reports I've read, several folks have reported previously non-leaking bikes started leaking immediately after converting to synth on classic Britbikes.

Also from reports I've read, several folks changing over have had no issues.

Take your pick.

 

[Migsan]

Migel,

You answered your own question - Removed the oil pump and was super clean had good vacuum and would squirt oil on both sides with good pressure.
When you removed the plunger pump did you dis-assemble and reseat the steel balls into the seating area? This done using a brass drift, seat the ball into its cavity and gently give it a tap. This reseats the ball into the cavity, and do not over tighten the end caps. You will find the oil pressure will rise. Triumph T120/140 engines don't usually have high engine pressure and you can tell by watching the oil return line that comes up from the engine back into the engine oil reservoir. Steady stream is a good sign, sputtering oil return tells you the oil pump needs to be reseated and the crank sludge trap needs servicing.
Just one question about your engine rebuild did you remove the dreaded crank oil sludge trap? This is a must when ever you do an engine rebuild!
Good luck in your quest and you will find these engines are robust if maintained properly and use only 20/50W petroleum oil and not synthetic!
Merry Christmas and may you have a fruitful New Year.

That's good information that I will hold for future issues. I ended up replacing the pump in the process.
indeed everything seemed fine on the old pump but being the first time checking it I just wasn't 100% sure.
yes the sludge trap was removed and cleaned!
Thank you for the help!
Have a great Christmas and a Happy New Year

 

[Migsan]

Regarding this matter is it truth that synthetic oil, besides the temperature stability, will allow the suspension of particles and therefore be more adequate to use with modern filtering systems?
thanks

 

[Rudie]

is it truth that synthetic oil, besides the temperature stability, will allow the suspension of particles and therefore be more adequate to use with modern filtering systems?

No, any oil will do that; until replaceable filters that would not restrict oil flow could be made small enough, a common way of 'filtering' particles collected during circulation through the engine was a large oil reservoir; the oil spent a relatively long period in the reservoir between circulation, allowing many particles to settle to the bottom of the reservoir.

The Triumph twin engine is archaic in not having a replaceable full-flow filter. After the prototype triple engine in the early 1960's, succeeding developments incorporated a filter. A filter was added to 71 singles. All long before synthetic oil for road vehicles was widely available.