Assuming by "base nuts", Kevin means cylinder base-to-crankcase. There's no explicit call to re-torque these, and 35 ft.-lbs. sounds like a lot. My A65 service manual specifies 21-22, and I would think Triumph would be about the same. In fact, I've never used a torque wrench there, as you would need a special tool on some of them; I just get them as tight as I can with a normal-size 1/2" ring spanner. The only "squish factor" is the gasket, as the cyl barrel is cast-iron. IOW, I wouldn't loosen them to re-torque, just re-check with a wrench to ensure they haven't loosened. If the studs and nuts are clean and in good condition, they probably won't.
35 foot-pounds is a lot, compared to the 15 and 18 needed for the head. but that's what the factory manual specifies for the 650s. i don't know if that ever changed for the T140s-- in 1973 they didn't print a spec.
i check torques on things separated by gaskets routinely, anyway. on this one i'm chasing oil leaks, not successfully yet.
...79 manual specify 20 lbs for those nuts, but is like Mark Z is saying; you do not need a torque wrench. Also 20 is similar to adjust with a wrench. No leaks in that part; even in my 48 500 daily rider.
It's not that you will distort the barrel but you will heavily stress the aluminium case which the studs are pulling on (and hopefully not through) if it's your race motor you have a lot of compression force trying to lift that barrel up. Key thing with anything is making sure all studs are tightened equally.
If my motor is out of the frame when I do the barrel then I do torque ALL the nuts. However with a double down tube frame it isn't easy when the motor is in.
Can't argue with the manual (or can I?)... 35 still seems like a lot for 5/16" studs though.
Yer ahead of me with the torque wrench adapter. An absolute need for A65 cylinder head nuts, but I didn't expect to hear someone make one for the cyl. base nuts.
For the life of me, I can't remember the formula I used to get the torque differential on my A65 cyl. head nut adapter, but the result was 27 ft.-lbs. to get the required 32, and my adapter is only two inches long. Added to the 12" torque wrench, that brings the total to 14".
Kevin, if the threads in the aluminium case are at their limit they will go ping. (Having them all torqued equally reduces this, as usually the weakest goes first) think of the cover screws when some DPO nerk has over tightened them and the threads came out with the screw.
At this point I'd be asking John Healy to chime in, he may turn around and say the 35 ft lb is correct. But I would rather have his take on this than just trust the book
its not unknown for factory torque figures to be wrong, there is now a thriving market in OIF fork slider end caps because the manual says 35 ft lb for the end cap nuts ( 5/16" UNF). Copied over from year to year be seems a bit unlikely , but, not many people had torque wrenches BITD so who knows?
35 ft lb. It does seem awful high for a 5/16" fastener, my 3/8" head bolts only get to 30( A65). 18-20 would be a more common value in this situation. TT must know this one.
Last edited by gavin eisler; 08/01/167:01 am.
71 Devimead A65 750 56 Norbsa 68 Longstroke A65 Cagiva Raptor 650 MZ TS 250 The poster formerly known as Pod
On my '64 TR6R, the studs for the cylinder base are 3/8" diameter, not 5/16".
The Factory_Service_Manual calls for 35 lb.ft., but Tom Gunn's Engine_Overhaul_Manual says 25 lb.ft. I went with the more friendly 25. I used HondaBond4, with no gasket at the base of the cylinders. I never re-torqued these fasteners. Some 5,000 miles and the joint there is still bone dry.
I made up a couple of wrenches for the base stud nuts on the cylinders by ordering an extra 1/4 x 5/16 W ring spanner from British Tools & Fasteners, and bought a cheap set of crow's foot wrenches from Menard's in 3/8" drive:
Then I cut the wrench in half and ground flats on the shank to fit the two smallest crow's foot wrenches:
I also ground down the box (ring) end so that it will clear the cylinder fins:
Then I got a friend to weld them together as shown here (lower right). I also daubed on some paint to keep them from rusting.
Keeping the extension at 90° to the body of the torque wrench lets you read the torque directly per the wrench setting, since torque is the product of the applied force times the perpendicular distance from the line of force to the center of rotation.
If, on the other hand, the extension is used in a straight line with the wrench body (or at any angle other than 90°), the "moment arm" is lengthened and it becomes necessary to use ratio and proportion to calculate a lesser wrench setting.
'64 TR6R Plus some Twins from other countries (U.S., Germany, Japan)
Also what s the math to know that you use a wrench and the extension with 27 to get 35?
lol. i have no brain. i just went over and looked. the base nuts on the T120s are all 3/8-inch, not 5/16-inch.
my torque wrench is 14 inches long, and the 1/2-inch wrench i use as an extension is 5 inches.
so when i put the extension on, it becomes an almost-19-inch wrench. to reduce the torque reading, i just subtract 5/19ths of 35 from 35, and get 25.7 foot-pounds (oops, not 27) on the wrench. or sometimes i use it at 90 degrees as well, which technically requires a slight pythagorean correction but in practice is too small to measure.
...since this morphed in a "what torque thread"; I want to ask what s exactly the torque to apply; because the manual specs are for DRY; but normally in most situation oil; grease or special lubricants are added...