73 Tiger 750 TR7RV - Much Improved

[speedrattle]

what does that "butchered hole" in the case look like?

i routinely file notches in the inner primary chaincase to allow me to fit 21-tooth gearbox sprockets. you can fit a 20 through the hole as-is, but thats it. a 22 requires you to hold it up there while you stab the gearbox mainshaft through. not easy, and not much point. very few 650s go 138 mph.

if you are halfway careful, you can file notches to fit the 21 while not disturbing any of the screw holes that hold on the trapdoor. if you are fitting a dry primary belt-- not all belts run dry-- then you can leave the trapdoor cover off.

i install a seal if i run a dry primary, and plug the three holes. this requires different crankcase venting.

if you keep the original open main bearing without the seal, then the three holes are mostly decorative. the only way that the oil level ever gets high enough to pass more than mist through them is if you have an overfill condition in an OIF tank and fill the primary through the forward breather line or similar. thats an issue only temporarily, as the excess oil will quickly be blown back into the crankcase through the open main bearing.

 

[NM Bonny]

Politely, this does not read correctly.

When Triumph changed the twins' crankcase venting - first engines late in the 69 model year, first drawn and listed in the 70 parts books - specifically the drive side main bearing oil seal was not fitted so that the crankcase could vent into the primary case. The main bearing seal was still drawn and listed in some versions of the 70 twins parts books but that is a misprint, the seal was never fitted.

The drive side main bearing oil seal was only fitted to earlier twin engines in conjunction with the hollow inlet camshaft driving the timed breather in the drive side crankcase, that vented by the gearbox final drive sprocket.

Primary oil level is self regulating only in engines venting through the drive side main bearing. Earlier engines, primary oil level must be set using the level hole towards the front of the primary chaincase.

Rudie,

I am glad to learn this because I'll soon be removing the primary on my '71 Bonneville 650 to install a three-phase Lucas alternator, inspect the primary, clutch, replace the rubbers and the final drive front sprocket with a new 20T version (and new tranny output shaft seal).

However, let me make sure I understand, please: aside from oiling the primary chain after inspection or replacement and installing the cover, I should not be introducing any volume of oil into the primary chain chamber. And instead merely adding the appropriate amount of oil to the sump and oil tank when refilling. Correct?

It sounds like the primary is oiled by oil (and vapor) venting through the main bearing--which has no oil seal--and that any excess buildup would return to the sump via the three holes. Or am I misunderstanding how the three holes work?

 

[Rudie]

However, let me make sure I understand, please: aside from oiling the primary chain after inspection or replacement and installing the cover, I should not be introducing any volume of oil into the primary chain chamber. And instead merely adding the appropriate amount of oil to the sump and oil tank when refilling. Correct?

It sounds like the primary is oiled by oil (and vapor) venting through the main bearing

No, the Triumph manuals (workshop and owner's) list 150 cc of engine oil to be added to the primary chaincase; this should ensure the primary chain is lubricated by running through some oil during part of the bottom run. This also splashes the oil around the primary compartment so some runs over the clutch to lubricate its rollers.

It sounds like
any excess buildup would return to the sump via the three holes.

Some oil does enter the primary chaincase through the main bearing, as droplets vented from the crankcase; however, the better the sealing of the piston rings on the bores, the less oil in the vented vapour, so this is not a certain way of lubricating the primary chain and clutch rollers.

Any oil vented from the crankcase should condense in the primary; however, even if oil vapour entered the original primary breather around the rear fender, as long as the oil condensed before the highest point of the breather hose, it drains back to the primary compartment.

Finally here, the o.i.f. also vents into the original primary breather around the rear fender, from the underside of the large diameter tube near the headstock; this is also usually vapour but can be oil under hard braking.

So, after 150 cc of oil is added to an empty primary compartment, the oil level could rise. The level of the three small roles from primary to sump should be just below the bottom of the alternator rotor; the three holes will allow oil reaching them in the primary to drain back to the sump before the oil can drag on the alternator rotor.

 

[NM Bonny]

No, the Triumph manuals (workshop and owner's) list 150 cc of engine oil to be added to the primary chaincase; this should ensure the primary chain is lubricated by running through some oil during part of the bottom run. This also splashes the oil around the primary compartment so some runs over the clutch to lubricate its rollers.


Some oil does enter the primary chaincase through the main bearing, as droplets vented from the crankcase; however, the better the sealing of the piston rings on the bores, the less oil in the vented vapour, so this is not a certain way of lubricating the primary chain and clutch rollers.

Any oil vented from the crankcase should condense in the primary; however, even if oil vapour entered the original primary breather around the rear fender, as long as the oil condensed before the highest point of the breather hose, it drains back to the primary compartment.

Finally here, the o.i.f. also vents into the original primary breather around the rear fender, from the underside of the large diameter tube near the headstock; this is also usually vapour but can be oil under hard braking.

So, after 150 cc of oil is added to an empty primary compartment, the oil level could rise. The level of the three small roles from primary to sump should be just below the bottom of the alternator rotor; the three holes will allow oil reaching them in the primary to drain back to the sump before the oil can drag on the alternator rotor.

Okay, thanks for the clarification - but is it 150cc or 150ML of oil into the primary chaincase...?

I'll amend my maintenance/inspection notes, and am looking forward to getting a warmish day to get this bike rolling. Happy Holidays!

 

[Rudie]

150cc or 150ML

Same thing.