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Originally Posted by henryanthony
In the J.R. Nelson book, "Bonnie", changes to the 1970 engine includes, "Engine breathing was now achieved by drilling three breather holes in the drive side crankcase below the main bearing housing, allowing pressure relief into the primary chaincase chamber, at the same time maintaining a constant residual oil level in the chaincase."

The three holes are far too small to be "breather" holes and as already mentioned they are far too high to be "level" holes.

Originally Posted by henryanthony
Changes to the 1971 engine includes, "A new engine drive sprocket without the ground oil seal shoulder face and an associated distance piece to compensate for the fitting of primary chain alignment shims, was introduced to ensure more positive and accurate chain alignment. The drive side crankshaft seal was deleted.

Other authors say 1970. JR Nelson says 1970 in his Tiger 100/Daytona book.


Originally Posted by henryanthony
Could it be true that elimination of the oil seal had nothing to do with engine breathing?

I'd say removing the seal had everything to do with engine breathing as the three tiny holes on their own would be useless.

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Hi, Of course removing seal had to do with breathing. Thing is managing pressure inside the crank case is important for power. It it well know in racing motors that unwanted crank case pressure can rob horsepower. Lots of mods were/are used to improve crank case pressure. Racing is simple really as how long is the longest race? It only needs to work that long.

Street bikes must stand the test of time with only the simple maintenance, basically no maintenance other than changing oil. That's a lot more complicated. For sure primary breather essentially eliminated oil being spit on the street as the timed cam breather could do. I have no idea which gave more power.

Interesting John's observation on T120RT primary chain issues. The 3 row on T140 seems to last fine. I can see how 2 row would give more power as there is less mass to move & less frictional losses. Again it only has to last long enough to win the race. Do the math. .1 MPH faster on 50 lap race. How many feet is that? Depends on course, but how often is 1st & 2nd place within 2'. Any slight advantage in racing makes a difference. Any!

Street bikes are another thing. Good running & strong performance is a must, but long service life & Trouble free operation is very important. Triumph for as bad as they are were fast & as trouble free if not more & lasted slightly longer than many British makes. A very important thing was a good dealer network that did good work. Even in the early 60s when I was old enough to ride my bicycle to look at bikes, Triumph, Harley dealerships were head & shoulders above all others. The Japanese makes partnered with Triumph dealers best they could for this reason.

No British make kept up with progress, even though they knew they should in engineering.

The Primary breather was a big improvement over the oil puddle from timed breather.

Still.... How did they figure out the placement of the 3 holes & exactly how is oil level regulated.

Web search of Dickie Bender comes up empty for me. I had a ray of hope an interview or something would show up. Anybody have an success in searching for Dickie. I don't know if he's still with us here on earth or not. Anybody know & could ask him?
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There is a Cycle News article from January '81 that mentions the passing of a Richard Bender that received the P.A. Sturtevant Company's Master of Mechanics Trophy.


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Seems as if we hadn’t had this discussion at all!

I would have imagined by now that it would have been realised that chaincase level control isn’t by any simple liquid drain.
Eliminating that mechanism leaves the oily vapour exchange as the only available alternative (other than magic).

As the 3 holes are at most only about 2% of the available open area of the main bearing, I don’t think they have any significant role in breathing.

I can only think they are present at all, and more precisely where they are, is to provide a minimal level of lube to the chain, should the level in the chaincase be below chain level (so it wouldn’t be generating the normal splash).

They seem to be roughly in a position to spray oily vapour onto the chain just before it goes over the tensioner blade.
This is the only frictional surface for the chain.
Triumph may have been concerned that this should never run dry.
It has been mentioned that earlier unit models had the trough/tube arrangement feeding the chain, possibly for this reason?

Was the trough/tube eliminated when the later system was adopted? If so, I can see a reason for the 3 holes in that position.

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Originally Posted by koan58
It has been mentioned that earlier unit models had the trough/tube arrangement feeding the chain, possibly for this reason?

Was the trough/tube eliminated when the later system was adopted? If so, I can see a reason for the 3 holes in that position.

No, not until sometime during 1978 as the tube and parts are in the '78 parts book but not the '79 book and my late '78 model (the crankcase in my previous photos) doesn't have it.

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Originally Posted by TR7RVMan
Hi, Of course removing seal had to do with breathing. Thing is managing pressure inside the crank case is important for power. It it well know in racing motors that unwanted crank case pressure can rob horsepower. Lots of mods were/are used to improve crank case pressure. Racing is simple really as how long is the longest race? It only needs to work that long.


Don
Ha, not exactly...the engine needs to survive intact, not with the crankshaft red hot and smoking laying there on the racing surface.


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Thanks for that LAB, as you will have realised I don't know much about the units!

However, I still think the purpose of the trough/tube and 3 holes may have been similar, if over-lapping.

The leading edge of the tensioner blade is the most frictional surface in the chaincase.

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My take on this mechanical mystery is that the crankcase acts like an oil mist generator. Those with industrial experience with oil mist systems will see the similarities. Every crankshaft revolution experiences a 650 cc. decrease and increase of volume in a sinusoidal cycle. The resulting pressure pulse breathes out then in through the left side bearing cage. The outflow carries oil in aerosol and larger droplets through the bearing cage, back and forth. The three tiny drillings won't carry much vapor at the pulse speed that the engine generates. Oil mist deposits oil droplets on stationary surfaces which then drips to the bottom of the primary. The rate of deposition is unknown, but eventually liquid oil will flow back into the crankcase through bearing cage and drilled holes. The air-oil mixture sucked back to the crankcase will have less oil, and at equilibrium the oil will flow through the tiny holes. Till equilibrium is reached liquid oil will accumulate in the primary and flow through the bearing cage. Excess oil hanging around in the primary will lube the primary chain, clutch plates and clutch bearings. The net flow of oil back into the crankcase is evidently very small, as evidenced by the small flow area of the holes. In practice the hole area probably doesn't matter much but only affects how quickly equilibrium liquid oil volume is reached. Of course, it will change all the time with varying crank speeds. At the end of all this huffing and puffing, the net outflow of vapor out the vent pipe only equals the blow by from piston rings. On shutdown, everything will drain to the bottom of crankcase or primary case and in that condition the holes will let excess oil drain to the crankcase if the primary level is higher. In the overall scheme of things, the primary is just a strange resonating chamber in a dry sump oil system.

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Originally Posted by John Healy
Breathing through the primary, and the three holes, was originally done by Dickie Bender (TriCor Service Tech), on the 750 long rod bikes he prepared for Gary Nixon for dirt track.This was before Triumph pick up on it. Dickie Bender, who was given Mechanic of the Year

As a dealer we didn't start having primary chain problems under warranty until they introduced the T120RT. Not a lot, but if you had an engine that was lugged a lot we would see some problems. Thus I believe the reason for the triplex chain when they introduced the T140 short rod. We always used a duplex chain on the 750 short rod racers we built. We were lucky enough to find some HP and never had a chain problem.



Interestingly, Stan Shenton advised drilling the 3 holes on trumpets, in line with the chain....................................(tuning for speed)

A bloke i knew who raced a pukka 66 or 67 Thruxton bonny used to top the oil level up by adding
to the primary case as otherwise you had to remove the seat to access the tank. So triumphs used
the setup before '69 on race bikes.

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Hi, I don’t believe the oil is just running back. The holes are too high & overfill lowers much too quickly.

Somehow it gets sucked back.


Here’s a question. Suppose you blocked holes... replaced cover. Added 150cc oil. Rode bike 300 miles in every day riding. Some city, some highway, some canyon riding.

What would primary level be?

With the 3 holes it only varies by 1/4” or so. On rare occasion it can get near an inch deep. Mostly I see it at about 1/2”.
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Originally Posted by henryanthony
In the J.R. Nelson book, "Bonnie", changes to the 1970 engine includes, "Engine breathing was now achieved by drilling three breather holes in the drive side crankcase below the main bearing housing, allowing pressure relief into the primary chaincase chamber, at the same time maintaining a constant residual oil level in the chaincase."

Changes to the 1971 engine includes, "A new engine drive sprocket without the ground oil seal shoulder face and an associated distance piece to compensate for the fitting of primary chain alignment shims, was introduced to ensure more positive and accurate chain alignment. The drive side crankshaft seal was deleted.

Could it be true that elimination of the oil seal had nothing to do with engine breathing?

The 1970 parts book includes the oil seal. In the 1971 parts book, the oil seal is deleted.

However, we all know, or should know, the accuracy of Workshop and Parts manuals is subject to errors.

Regarding comment by JH, I have also read that the three holes were performance related with regard to air volume beneath the pistons. If I can find the thread again I will post a link.

The three holes existed in 1970, as did the seal. Which begs the question: what oil was specified for the primary chaincase in 1970?

Can't one of the more enthusiastic Britbike members install some pressure sensors and some datalogging?

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Originally Posted by NickL
Interestingly, Stan Shenton advised drilling the 3 holes on trumpets, in line with the chain....................................(tuning for speed)

Phil Irving also used the title Tuning for Speed, for a book.


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Originally Posted by Dibnah
The three holes existed in 1970, as did the seal.

The seal "existing" for 1970 seems to be an error. JR Nelson saying the seal was removed for 1970 in his Daytona book.


Harry Woolridge says in his Triumph Trophy Bible for '1970'

"A revised breather system required a drive-side crankcase with three holes below the main bearing housing, maintaining a constant oil level in the primary chaincase.* To allow engine breathing, the oil seal between the crankcase and the engine sprocket was deleted.".

*(or not, as the case may be?)

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My '70 T120 Bonnie had no seal. I know because I fitted one and drilled a 1/2" hole next to the main roller bearing. I did this because I was concerned that a bearing issue I'd had might have been caused by contamination getting into the bearing with the blowing and sucking through it. The mod made no difference to the self levelling in the primary.

I was able to fit a seal, where there had not been one before, because the '70 casing was still being machined to take one and the crankshaft pulley was machined to run in a seal, as had been done with pre '70 models.

The '70 parts book did indeed show a seal (E3876), I've just checked a '70 T120R parts book and it is there. The rest of the later breather system is correctly shown. The crankcase also had the 3 small holes. I can confirm No Seal was fitted as the engine was originally built. This is clearly another Triumph error in the Parts book.


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In a running engine, any oil level above the bottom run of the chain will be picked up a thrown around the case. Some will run down the case again and some will be a mist carried in the air. The crankcase also has a mist from the oil being thrown off the crank. The air/mist in the crank case and primary are exchanged with each up and down stroke of the pistons. After a time the mist in the primary will equalize with the mist in the crankcase so when the engine stops the oil drains back down in the primary and this is what you are measuring. If you check it right after running it will be low because there is still oil on the walls that has not drained down. Any oil lost through the vent pipe will decrease the amount of oil in the mist which will be increased again by oil from the crankcase mist. If you overfill the primary the oil content of the mist will be higher and it will be exchanged with the lower oil content of the crankcase mist. After a long enough run the primary oil will be back down to its normal level.
The three holes are likely an attempt to blow oil onto the primary chain. Oil should be introduced to the inside of the chain which is what the original catch cup and pipe did. Blowing oil on the side of the chain is not as effective.

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When I bought the 72 it had a LOT of problems so I was always tearing it down. The first year it did more miles in the back of my truck then on the road. When I put it back together I would put 350 cc's of oil in the primary "like the book" said, then I would go for a very short ride just to test for leaks and see if I had actually fixed anything. That excess oil was quickly sucked out of the primary and back into the crankcase where it was just as quickly pumped back into the frame. When I unscrewed the cap, oil would go everywhere. I quickly learned to keep a turkey baster handy to remove what was left, made for some interesting Thanksgivings. That's when I first start asking the question that started this thread. I'm not sure I know yet.


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yep , +1 to what dmadigan said ... and to what others are alluding too .


the amount of air blown into the primary is equal to the amont of air sucked out of the primary .

but the amount of oil-mist made by the crank-case (blender )
... is not equal to the amount of oil-mist made by the primary-chain (blender )

so the oil mist moves to the side with less density . ( gas equilibrium )

more oil moves back to the crankcase ... when the primary oil level rises
more oil moves to the primary ... when chain level drops .
( somewhere in here ... the primary oil level finds a balance per rpm )

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Originally Posted by triton thrasher
Originally Posted by NickL
Interestingly, Stan Shenton advised drilling the 3 holes on trumpets, in line with the chain....................................(tuning for speed)

Phil Irving also used the title Tuning for Speed, for a book.


Ah yes, Triumph Tuning by Stan Shenton. I think was the runner of the Boyer racing team, not sure though.

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Hi All, Did a 70 mile ride today & did a few experiments. Also I did some checking of primary oil motor off.

First motor off. With motor off & you let bike sit until it cools some, the oil on clutch & walls of primary, chain etc. drain down. It does not continue to fill or empty at this point. It stayed the same level.

Motor stopped on side stand the oil level lowered about 1/4" as the dip stick is against inner wall. That is what I'd expected.

After last week I topped oil with heat soaked motor & frame to even with lower rear edge of filler neck. This is right on full mark on my dip stick (hooked into filler cap).

I rode 22 miles & pulled over on level parking lot. Checked oil, not fully warm. Still a little under the neck. Idled motor maybe 20 seconds bike vertical & level on center stand. RPM 1000-1050. Occasional blipping of throttle if motor wants to slow.

Oil maintained level, return tube spurts very even.

Took bike off center stand & put on side stand. Looked like oil return stopped.... then ok. Oil level in frame started to drop rather quickly. Dropped about 3/4-1". Then seem to stabilize. Let it idle a full 3 minutes. No smoke. Wasn't sure but oil level continued to drop, but very slowly. Hmmm.....

Put filler cap back on & road bike to next parking lot about 5 miles. Oil level was about 1/2" lower than neck so had come up some, but not all the way. Again on side stand dropped quickly about an inch, but since it started lower it ended lower. Put cap on & continued.

Next stop was about 12-15 miles. Oil was nearly to bottom of neck & motor was getting heat soaked. Again on side stand, quick, then slow drop.

Next stop was home & garage with proper light ruler etc. I'd done several miles open highway 55-60 mph & some canyons & some city. Pulled into garage without shutting off & put on center stand, with bike level. Motor, frame, oil all heat soaked. (90f) Oil right to bottom of neck this time.

This time I had cap off the whole time, rolled off center stand. Let idle, oil level stable. Revved motor some level still stable. Let idle again, oil level stable.

Rolled off center stand & carefully watched return spurts. Put on side stand. Moment later oil return stopped, then started again. 1-3 seconds. Now level started dropping quickly. About 3/8-1/2" I put bike vertical. Dropping stopped, spurting was more volume. Oil level came right up. Tried this again but let it drop about 1" only 20-30 seconds, put bike vertical. Oil came back up, but not quite as much....

Put on side stand again for 3 min. Went down quickly as expected, then slowly as before. Yet again put bike vertical, oil came back up. However... this time oil stayed a full 1/4" lower than neck. Even with some revving it stayed the same.

Doing some more experiments, revving motor makes oil rise faster as expected.

No smoke ever from either exhaust pipe.

Conclusions... The lack of spurts is pump sucking air as oil now starts to puddle away from suction tube. In a few seconds, suction tube gets some oil, but as motor runs the oil continues to pool on left side of crank case until it has enough to spill over to the suction tube. Putting bike vertical the return pump quickly empties the pooled oil & all is back to normal.

When I wait 3 minutes I think?? oil is transferring to primary case. That's why it doesn't return to full in frame. But after riding several miles & primary self levels oil is to full mark again.

I'll have to do confirmation tests with dip stick on primary.

Truth be told I did expect oil to transfer into primary case that quickly at idle.

Another question which this seems to lead to a yes answer is if motor sump has too much oil, does that make primary oil too high? I still don't know, but from the very little testing I've done so far, it's looking that way. Still we mustn't jump to conclusions. They must be verified.

To be continued..... when time permits. Anybody else want to jump on board & do some testing, I'd appreciate to see your results. Thanks!
Don


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We need minicams inside the frame and the primary chaincase wink

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Originally Posted by Dibnah
We need minicams inside the frame and the primary chaincase wink

With tiny screen wipers.


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Here is a pic showing the position of the three small holes on a T100 500 with the alternator in position. A PO had fitted a belt drive, which has now been removed and the conventional chain drive fitted after a belt failure.

The chain effectively runs in the same position as the belt had been, so any oil or oil vapour coming through the holes would be a little above the inside of the chain. Incidently, the 500's were not fitted with the trough and pipe arrangement of the 650's/750's.

https://ibb.co/0BBPRw3


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Just read an interesting article in this months Classic Bike magazine where it described the exploits of Buddy Elmore's win in the 1966 Daytona 200 on a Triumph T100. Apparently it was Hele himself who initiated the deletion of the drive side main oil seal for breathing purposes and introduced the mysterious three holes to provide extra lube to the primary chain. Unfortunately it doesn't go into any detail on primary oil level.

"Because the T100 crankcase breather - a timed valve on the inlet camshaft venting to atmosphere - might not be able to cope with the increase in rpm, Hele adopted the solution used on Triumph's ISDT bikes. The timed valve was discarded, along with the oil seal from the drive-side roller bearing. This allowed the crankcase to breathe through that bearing into the primary chaincase, which was vented to atmosphere by a big-bore clear plastic pipe. Three 1/16" (1.6mm) holes were drilled in the crankcase wall, level with the bottom chain run, so that oil mist would spray onto the chain."


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Originally Posted by TR7RVMan
Hi All, Did a 70 mile ride today & did a few experiments. Also I did some checking of primary oil motor off.

First motor off. With motor off & you let bike sit until it cools some, the oil on clutch & walls of primary, chain etc. drain down. It does not continue to fill or empty at this point. It stayed the same level.

Motor stopped on side stand the oil level lowered about 1/4" as the dip stick is against inner wall. That is what I'd expected.

After last week I topped oil with heat soaked motor & frame to even with lower rear edge of filler neck. This is right on full mark on my dip stick (hooked into filler cap).

I rode 22 miles & pulled over on level parking lot. Checked oil, not fully warm. Still a little under the neck. Idled motor maybe 20 seconds bike vertical & level on center stand. RPM 1000-1050. Occasional blipping of throttle if motor wants to slow.

Oil maintained level, return tube spurts very even.

Took bike off center stand & put on side stand. Looked like oil return stopped.... then ok. Oil level in frame started to drop rather quickly. Dropped about 3/4-1". Then seem to stabilize. Let it idle a full 3 minutes. No smoke. Wasn't sure but oil level continued to drop, but very slowly. Hmmm.....

Put filler cap back on & road bike to next parking lot about 5 miles. Oil level was about 1/2" lower than neck so had come up some, but not all the way. Again on side stand dropped quickly about an inch, but since it started lower it ended lower. Put cap on & continued.

Next stop was about 12-15 miles. Oil was nearly to bottom of neck & motor was getting heat soaked. Again on side stand, quick, then slow drop.

Next stop was home & garage with proper light ruler etc. I'd done several miles open highway 55-60 mph & some canyons & some city. Pulled into garage without shutting off & put on center stand, with bike level. Motor, frame, oil all heat soaked. (90f) Oil right to bottom of neck this time.

This time I had cap off the whole time, rolled off center stand. Let idle, oil level stable. Revved motor some level still stable. Let idle again, oil level stable.

Rolled off center stand & carefully watched return spurts. Put on side stand. Moment later oil return stopped, then started again. 1-3 seconds. Now level started dropping quickly. About 3/8-1/2" I put bike vertical. Dropping stopped, spurting was more volume. Oil level came right up. Tried this again but let it drop about 1" only 20-30 seconds, put bike vertical. Oil came back up, but not quite as much....

Put on side stand again for 3 min. Went down quickly as expected, then slowly as before. Yet again put bike vertical, oil came back up. However... this time oil stayed a full 1/4" lower than neck. Even with some revving it stayed the same.

Doing some more experiments, revving motor makes oil rise faster as expected.

No smoke ever from either exhaust pipe.

Conclusions... The lack of spurts is pump sucking air as oil now starts to puddle away from suction tube. In a few seconds, suction tube gets some oil, but as motor runs the oil continues to pool on left side of crank case until it has enough to spill over to the suction tube. Putting bike vertical the return pump quickly empties the pooled oil & all is back to normal.

When I wait 3 minutes I think?? oil is transferring to primary case. That's why it doesn't return to full in frame. But after riding several miles & primary self levels oil is to full mark again.

I'll have to do confirmation tests with dip stick on primary.

Truth be told I did expect oil to transfer into primary case that quickly at idle.

Another question which this seems to lead to a yes answer is if motor sump has too much oil, does that make primary oil too high? I still don't know, but from the very little testing I've done so far, it's looking that way. Still we mustn't jump to conclusions. They must be verified.

To be continued..... when time permits. Anybody else want to jump on board & do some testing, I'd appreciate to see your results. Thanks!
Don

i have done similar running on new to me 71 tr6c, and seen same things happen
2 morals here - dont let it idle on sidestand and check oil after running a few min.

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Entertaining three pages.

Seems to me, the obvious features of this design are, the three holes are at more or less the highest level of the lower run of the primary chain where it runs over the tensioner, while the chain goes about 1/2 inch above the bottom of the case at its lowest point, below the clutch sprocket--the level that the oil seeks for itself.

Thus, the only answer can be that the three holes at the level of the chain atop the tensioner take oil carried by the chain back into the crankcase due to the pulsing of crankcase pressure in and out of the chaincase. And the oil is picked up by the chain at the level of the lower run of the chain at its lowest point, behind the tensioner, basically below the clutch sprocket, about 1/2 inch above the bottom of the chaincase. The chain picks oil up from lower in the case, setting the level low, and carries it higher, up over the tensioner, and then out the holes. That is, the level is set lower, by holes higher, because the chain works as a sort of water wheel, carrying oil from low in the case, 1/2 inch off the bottom about where it is under the clutch sprocket, to a point higher in the case over the tensioner at the level of the three holes, where it is blown/sucked back into the crankcase and scavenged back to the oil tank. This is not a super efficient process, it takes a little time to adjust itself, and the levels are only approximate, but it works well enough.

Perhaps the proof of the pudding is in the eating--the parts work precisely as designed.

Last edited by linker48x; 06/15/21 12:16 am.
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