[StuartMac]

Hi,

1967 T120R motor
stator wire comes out of the primary case differently than my other build. Rather than coming out of the top of the case, it comes out centrally and drops down through the area where the drive sprocket is housed. So, I am wondering the best way to route this back up to the top

Triumph 350/500 workshop manual, .pdf page 51 shows the wires passing through a clip bolted to the underside of the engine; however, I cannot find the clip shown or listed in parts books :-

. If your Rickman's engine has a threaded (1/4"BSF?) hole in the correct position, try the 70-1509 "Clip" normally used on the stator cable inside the primary?

. If your engine doesn't have a usable threaded hole in about the correct position, I'd pull the alternator cable relatively tight and zip-tie it to the timing-side frame tube under the engine, so the cable is pulled as far away as possible from the chain and sprocket.

However you are able to secure the alternator cable, the bullet terminals are likely to be under the engine ... I'd cut 'em off and replace with (a) modern waterproof connector(s) (say from jetski electrics?); however, select a connector type from which the thin individual terminals can be removed ... so, if you ever need to remove the stator from the primary, you can unclip the actual terminals on the ends of the wires so they can be pulled through the crankcase holes, you don't have to cut off the terminals, shorten the wires.

primary inspection hole/oil fill hole, the PO has this interesting device assembled, that is a valve of sorts. I’m wondering the purpose/utility of this device.
View attachment 800001

Educated guess says it's a one-way valve:-

. Engine builder has converted to '70-on-style vent-the-crankcase-through-the-primary - you should find the standard pre-'70 drive-side main bearing seal is missing and there are three(?) small holes hidden behind the primary chain lower run near the stator in View attachment 800013

. One-way valve'd prevent the crankcase sucking back through the primary when the pistons are ascending; however, not sure I see the point - hose from the valve spigot to the rear of the bike (similar to standard '70-on), the crankcase would actually suck the air-'n'-oil-vapour that'd just been vented, the hose end to atmosphere just allows the pressure pulses to be equalised?

. '70-on standard (no valve):-

.. allows any vented oil vapour that condenses in the hose to drain back into the primary;

.. frame oil tank vent hose is tee-d into the crankcase/primary vent hose, allows oil or condensed vapour to drain into the primary.

Hth.

Regards,

 

[StuartMac]

Hi,

off on my understanding

crankcase venting
found the 3 small holes that a PO must have drilled to vent the crankcase through the primary

Uh-uh, the crankcase vents into the primary through the drive-side main bearing. All triples and '70-on twins, then the primary case works as a plenum chamber, the air flow slows, oil droplets vented from the crankcase should condense and fall to the bottom of the primary. Plus, as I say, the oil tank vents into the primary and, certainly on the OIF, under braking, oil could run from the frame down the vent hose into the chaincase.

Chain primary, the bottom run must be through some oil, to lubricate the chain and it splashes the oil around to lube the clutch rollers. However, you don't want so much oil in the primary it reaches the spinning alternator rotor causing power-sapping drag. The three holes are to allow excess primary oil to drain into the crankcase before the level reaches the rotor, not to vent the crankcase into the primary.

3 small holes are too low to use with a chain. They are below the bottom chain run and so the chain won't receive any lubrication. I've attached your picture (rotated) and also a picture showing where they should be. They need filling with JB Weld or similar and re-drilling higher up.

Ime (small), the three small holes are in position for a belt primary? Then you don't want its bottom run through any oil, holes that low allow any oil that enters the primary to drain straight out again into the crankcase.

vent tube from the primary, that also exits through the bottom of the engine, is blocked off.

That would've been the original timed crankcase vent (as on your other engine?); the crankcase vented through the hollow inlet cam, which drove a vent that was open when the pistons were descending and shut when they were ascending.

possibly be a reason for the "steampunk" valve at the top of the primary?

Proverbial 'solution in search of a problem'? As I posted earlier, primary simply venting into a hose connected to the filler hole, hose routed to the back of the bike, the crankcase will simply blow and suck mostly the same air (in the primary and the hose), just the pressure pulses will go to atmosphere.

In the 1960's, before Meriden changed the twins' crankcase venting, leaving out the drive-side main-bearing seal and drilling the holes between crankcase and primary was such a popular 'tuning' mod. in the US, at least one of importers marketed an accessory screw-in filter to replace the standard primary filler plug.

engine is going into an oil in frame Rickman, so I'm trying to figure out how to attach the oil lines properly as well as how it is to be vented
"oil out" fitting to the OIF at the bottom of the engine
2 "oil in" fittings at the top of the frame.

Educated guess says:-

. View attachment 800029 feeds the engine from the frame;

. View attachment 800030 , one is the return from the engine to the frame, the other is the frame vent?

In the case of this engine, that was not built by me, it looks like the PO wanted to convert it to a 70's and later motor where the crankcase vents into the primary.

Mmmm ... as above, long before Meriden did it officially from late '69, crankcase venting into primary rather than through the timed breather was a mod. by racers, that spread to wannabes; GB had similar, with (before Easy Rider) owners aping road racers, bolting 'clip-on' handlebars half-way down the fork legs, gearshift and rear brake levers by the pillion footrests ...

Hth.

Regards,

 

[StuartMac]

Hi,

Left and right crankshaft bearings
did not realize there were about 3 different bearings for the left and right side of the crankshaft, marked CN, C2 and C3.

Waited for someone who knows more than me to post but ...

All ball and roller bearings need some internal clearance. However:-

. if the bearing inner race is an interference-fit on the shaft, that'll expand the inner race a little;

. if the bearing outer race is an interference-fit in the case, that'll contract the outer race a little;

. either or both will reduce the bearing's internal clearance, so you start with a bearing that has additional clearance before it's fitted - C3 - then fitting reduces its internal clearance to 'correct' for normal use.

Otoh:-

. if the bearing inner race is a slip-fit on the shaft, the inner race won't be expanded by fitting;

. if the bearing outer race is a slip-fit in the case (there is some external mechanical retention system), the outer race won't be contracted by fitting;

. if the bearing's internal clearance won't be reduced by fitting, CN has the 'correct' internal clearance to for normal use.

C2 has reduced internal clearance before fitting, 'fraid I don't know what'd enlarge a bearing to 'correct' internal clearance?

explain
how one determines which bearing to use in a 1967 T120R engine.

Aiui, Triumph spec'd C3 clearance on twins' main bearings; however, in the case of your bike's engine, that was 55 years ago, the aluminium alloy crankcase castings have both aged and gone through innumerable heat cycles - the bearing housings could be stretched - the crankshaft could be worn.

What you should do is measure both shafts diameters and cases bearing housings diameters with the appropriate micrometers, correct any ovality by machining then take the measurements to a bearing factor, he'll consult charts and mutter some incantations:-

. if you're lucky, he'll hand you the bearings that'll be expanded by your bike's crankshaft and contracted by its cases to normal internal working clearance;

. otoh, if you're unlucky, he'll tell you the shaft diameters are too small and/or housings are too large, undersize shaft(s) must be enlarged by some process (plating?) to minimum diameter x, oversize housing(s) must be reduced by some process (plating? sleeving?) to maximum diameter y then he can hand you the bearings that'll work.

Or you can ignore any of the above that's correct, order E2879 and E1591, hope for the best ... ignorance is bliss?

Hth.

Regards,

 

[StuartMac]

Hi,

Cylinder base dowels
purpose

Cylinder block's separate from crankcases but you need the block's vertical plane through the centres of the two bores to align with the crank centreline, and the tappets to align with the cam lobes. The dowels are (should be) a very close fit in the corresponding holes in the cylinder base; if everything's been machined accurately, the dowels should ensure the above alignments are closer than could be managed with just studs through all holes.

Hth.

Regards,

 

[StuartMac]

Hi,

Rickman gearing.
standard Triumph T120 engine
18 and a 19 tooth
49 and 60 tooth
rear
planning on using this mainly for trails and fire roads and a bit on the street.
what size front and rear sprockets to use

According to the '67 650 parts book, most variants were fitted with 19-tooth gearbox (except the TR6C (18) and T120TT (17)). However, all appear to have been fitted with 46-tooth rear; 49-tooth rear is three teeth more, about equal to one tooth less at the front (i.e. = TR6C) = I'd go for 19t front, 49t rear.

Hth.

Regards,

 

[StuartMac]

Hi,

ELECTREX WORLD LTD, CDI IGNITION, STK-102D

The biggest disadvantage with them is, depending on the version, either they don't generate anything for lighting or only a maximum of 65W (i.e. about 5.5 Amps @ 12 Volts), maximum generating rpm unstated.

Plus, iirc, 1968 FMVSS says any bike made after 31st December 1967 and sold in the US, at least the rear lamp has to remain illuminated even if the engine stops. It was what finally drove the wooden stake through the heart of Lucas ET electrics.

Secondly, use the Forum Search in various old-Britbike forums, including BritBike itself to look for "electrex" then make a decision based on the results you find?

Hth.

Regards,

 

[StuartMac]

Hi,

1967 T120R engine that was recently rebuilt, and a TR6 single carb head

Head and Cylinder Clearance Issue.
cylinder on
attaching the head and working out pushrod spacers
have way to much clearance between the cylinder top and head!.
head
top and bottom surfaced
old style pushrod tubes and seals
about 1/8 inch clearance between the head and cylinde
shold have about .030 clearance there including the copper gasket.

To be clear, the clearance should be not including the head gasket.

Also, the thirty thou. clearance figure comes from the infamous November 1969 Service Bulletin when just one of those square-/oblong-section white or translucent seals in View attachment 807058 was added to '69-on PRT, that use more-normal round-section O-rings that should've sealed (but didn't always ). With those square-/oblong-section white or translucent seals both top and bottom of the PRT, thirty thou. is the absolute minimum head-block clearance, because you're only compressing each seal by fifteen thou.; you can go up to sixty thou. clearance but somewhere between thirty and sixty is better.

not sure how to fix this. It would seem that what I need are shorter pushrod tubes.

If this was true, you'd also need shorter pushrods ...

head
top and bottom surfaced

An eejit has probably been there before you ...

Because material has been removed from around the combustion chambers, could be you just need a thicker head gasket to compensate. Btw, because material has also been removed from the rocker-box gasket surface, you'll also need thicker rocker-box gaskets ...

Three other things to check:-

. you have the correct-length PRT;

. the head is pre-'69, because the recesses in the head for the tops of the PRT and the seals are deeper pre-'69 than '69-on;

. the tappet guide blocks are the correct depth ...

... all the above dimensions and much, much more useful information in Vintage Bike Magazine » Push Rod Tubes ; only thing to note is "So what is a convenient way to check the crush?" only applies to '69-on heads/clearance; as I say, two square-/oblong-section seals, a bit more than thirty thou. "crush" is wise when the head bolts are torqued.

Hth.

Regards,

 

[StuartMac]

Hi,

been reading the article and it reminds me of the differences between some religious groups - ha - we believe in square rings, O-rings, wedding rings, etc.

I'm By "the article", you mean the Vintage Bike one I linked? If yes, you're :-

. the white and translucent rings in your View attachment 807058 photo. were fitted to twins up to the end of '68;

. actual circular cross-section O-rings were fitted '69-on, with different PRT and head machining;

. however, the '69-on O-rings didn't always seal, Meriden added one white/translucent ring to the bottom of each '69-on twin PRT, retained with a "wedding ring" because there wasn't any vertical space for the pre-'69 cup washer as in your photo.;

. btw:-

the infamous November 1969 Service Bulletin

... is Service Bulletin 324 that you also dealt with in your 1967/1969 Bonnie rebuild Desert Sled project thread - post #122 ...

heard differing advice about the head clearance, with and without the gasket

Can't be without the head gasket - if you measure thirty thou (for example) clearance without the head gasket, standard head gasket is eighty thou., what's compressing the seal when the head gasket's fitted?

Also note John Healy's advice in Vintage Bike Magazine » Push Rod Tubes :-

So what is a convenient way to check the crush?
If you were like me trying to measure the “crush” is a bit of a conundrum. That is until I remembered a late 500 head gasket is .025 in. thick (it is close to the amount of crush I want to end up with — .030 in.). If I placed the 500 head gasket on top of the standard head gasket and then offered the head it should rock a bit and I can use a couple of feeler gauges to see if I am near the .030 in. I am looking for.

Also bear in mind all triples use the 70-4752 square-section white/translucent seals and, later this year, I'll have owned at least one triple for 46 years ...

Engine case numbering issue
on the bottom of the cases that the primary side case has the numbers 433, and the timing side case has the number 926. So, I'm not sure where to find what these numbers refer to

The crankcase castings were numbered prior to machining because all holes were line-bored between the two castings, so crank, cams, gearbox main and layshafts - that all crossed between the two castings - their holes at each end lined up. The castings were obviously split after machining both for cleaning and building the engine, the numbers on each casting ensured castings that'd been machined together were built up into the same engine.

The numbers on each casting also identified the engine before completion in the engine build book; the VIN we know and love wasn't applied to a given engine 'til it was completed; this ensured, if an engine failed inspection before completion, it was identified but, as it hadn't had a VIN applied to it, there weren't any gaps in VIN numbers on the engines that went for assembly into bikes.

T120R DU45678
1967 engine. The primary cover was not on the machine but included in the parts. Now putting it together, The engine cover hex bolts that fit on the timing side do not fit on the primary side cover.

This is confusing. Do you mean the 1/4"-thread screws you're using to mount the timing cover, gearbox covers and primary cover on the crankcases screw into the threads in the timing-side crankcase but not into the threads in the drive-side crankcase?

If yes:-

. the 1/4"-thread screws are "socket cap screws" aka "Allen screws" ("hex bolts" have a hex. larger than the thread OD);

. the 1/4"-thread "socket cap screws" pass through the timing cover, gearbox covers and primary cover, screw into threads in the crankcase.

The hex bolts I have, and that fit on the timing side covers, are 20TPI

If you mean the 1/4"-thread socket cap screws are 20 tpi, that's UNC or Whitworth (British Standard Whitworth, not US "Whitworth" ).

since these don't fit on the primary cover

You mean, "since these fit through the primary cover but don't screw into the drive-side crankcase"?

can I assume what I need here are the 26TPI bolts?

Likely but you know the saying about "assume"? I'd check.

If the crankcase threads to mount the primary cover are 1/4"-26, they're BSF (British Standard Fine). Cycle is the same TPI but a different thread cross-section; if I must use Cycle-thread screws, I thread a corresponding 1/4"-26 Cycle tap into the holes first, flutes filled with grease, to draw out any swarf, prevent it becoming jammed in the bottoms of blind holes, potentially puncturing or breaking a crankcase thread, potentially causing oil leaks or cross contamination between crankcase and primary.

Hth.

Regards,