Topic: How critical are torque specs?

[mgzych]

So I'm acquiring tools for my first season of maintenance on my new-to-me '75 CB550F. I see a few pages in the manual that list torque specs for all the various fasteners, plugs, etc. so I figure I ought to buy a torque wrench. But the specs are wide-ranging; I can't find a torque wrench that would work across the entire range.

I'm wondering how important those torque specs are, and whether, categorically speaking, certain parts or systems are more sensitive to them than others. Is there   a rule of thumb or place to draw the line rather than measure the torque of every fastener secured?

Do I really need two...or one...or no torque wrench?

[goldarrow]

I have 1 small and 1 medium. 

[heyitsrama]

I used to be a guy who just made things fit to ship. But my buddy really drilled into my head that i need to follow torque specs for things, and I start to agree with him when we worked on a 4runner head rebuild. being that tiny vibrations that occur after an extended period of time I would hate to see more damage occur due to not following torque specs.

You also have to consider that if you don't follow torque specs you can over tighten and damage things, or have #$%* fly off when you're working on them.

an example of over tightening would be when we were working on a WRX and the PO had over tightened the lug nuts on the wheels, took my buddy a long time to get those out, and it was a pain in the ass, not to mention the nonuniform fitment of the wheel on the hub.

Hell even that new Mac Pro (trashcan mac) has torque specs for every single bolt that it uses.

I prefer to follow torque specs, i see that the quality of work for people that follow them is GENERALLY better than that whom don't.

I have multiple 1/2, 1/4, and 3/8th in.

 

[Whaleman]

The only things I use a torque wrench for are rod bolts, head bolts and main bearing case bolts. I have never pulled my rotor off the crank. All others are by feel. Dan

[Stev-o]

I'm wondering how important those torque specs are, and whether, categorically speaking, certain parts or systems are more sensitive to them than others.

Yes, absolutely. I don't use a torque wrench for many general maint tasks but wouldn't even thick of doing an engine rebuild without one.

[goldarrow]

I'm wondering how important those torque specs are, and whether, categorically speaking, certain parts or systems are more sensitive to them than others.

Yes, absolutely. I don't use a torque wrench for many general maint tasks but wouldn't even thick of doing an engine rebuild without one.

And the medium size does it

[kidrcth]

my torque wrench is 20-250in-lbs. pretty sure thats plenty for most things on the bike. Maybe except axle bolts.

[madmtnmotors]

A good torque wrench can also teach you the "feel" for proper torque.

You also have to consider that if you don't follow torque specs you can over tighten and damage things, or have #$%* fly off when you're working on them.

I see that the quality of work for people that follow them is GENERALLY better than that whom don't.

+1

[martin_uk]

It also helps if you do not use over size tools ie a 1/2 inch drive socket/ ratchet on a M6 bolt, much better to use a 1/4 drive,  as M6 are prone to stripping in ally.

Definately use torque wrench on head and crank, crank case, swinging arm, rear wheel spindle

[Dino]

Good torque wrenches are a worthy investment. I always follow torque specs on small engines. Get a foot pounds and an inch pounds torque wrench. The inch pounds wrench will be far more accurate at settings below 10 ft. pounds. For instance, most 6mm bolts torque to 9 ft. lbs. 12" in a foot, so 9x12=108 inch pounds. Don't buy cheap junk. Spend a little and get something that's accurate.

[lrutt]

Don't skimp, get a 1/4, 3/8, and 1/2.

You'll likely use the smaller one for cam caps etc. Good to use a TQ wrench in the middle of it's range, not at the extreme on either end. the 3/8 will be for a lot of general engine work, the 1/2 for heavy duty stuff. You will find that Japanese materials are not near as forgiving for excessive TQ. either the base material will strip threads or the fastener will strip or twist. The Jap material just seems to be softer compared to Brit or European bikes. And I've worked on a ton of them for a comparison basis.

As others have said, definately for engine work, not case covers. Things like swingarms on some bikes, or if a bike has a SSS, def want to use it there. Lug nuts really should be done that way. Trans work.

[calj737]

I've used a quality Snap-On for about 30 years. On these bikes, none of the side cover bolts/screws require torquing them as they're less than 8# and not stressed. But everything internal to the engine and the case bolts holding the halves together definitely need to be torqued properly. Aside from the suspension items, this is the only place I use them on these bikes. A quality 3/8" drive wrench is a very worthy investment.

If you don't plan to perform the engine rebuild yourself at some point, then ignore it. But no good tool box is missing a good torque wrench.

[kidrcth]

you can usually find pretty cheap name brand used ones, and have them calibrated. Its not very expensive.

i know a few mechanics that get rid of their torque wrenches instead of having them calibrated.

[70CB750]

I remember using wrench and fishing scale for some torque that was too small for my torque wrench 

[Don R]

Too often people will post about having broken off a fastener and how to remove it. Sometimes the fastener was already stretched by a ham fisted PO but on occasion it could be prevented.

[evanphi]

I have click-type 1/4 and 3/8 drives, and a digital 1/2 drive. The digital can also be used for calibrating the other two with the proper adapters.

[Gman]

I have the click type 3/8" and 1/2" wrenches, but what I find myself using most of the time is my digital torque adapter, which, if you read the comments/reviews, is supposedly very accurate. 

http://www.amazon.com/Powerbuilt-940963-Digital-Torque-Adapter/dp/B009MBG4MG

It's easy to use, has a wide range, and you can use whatever unit you want (ft/lbs, in/lbs, N-m, etc.)

Peace,
G

[Bodi]

Just ignore the torque spec for 6mm bolts if into the alloy case: they often strip with less. Tighten them securely but don't overdo it. There are a few 6mm bolts into steel (cam sprocket for example) that should get full spec torque. Other fasteners like the main bearing bolts (lower case bolts) and head studs should get spec torque. Chassis bolts as well. Larger bolts into alloy are OK with spec torque too, as long as you have the right one in the right hole: mixing them up leaves some with deep engagement and some with only a couple of turns.

[Ravie]

Just for S&Gs...

I use a cheap Harbor Freight for foot lbs and a Craftsman beam type for inch pounds. Nice feel.

[hotelstationery]

Like so many others I have two, one 3/8 and one 1/2.  I got them for doing critical items but as long as I have them I use them for anything with a torque specification; it doesn't cost anything to use them more often.

If it's a click type that requries you to turn the handle to set it, don't forget to back it off again when you're done.  Leaving it under tension isn't good for it's accuracy.

jeremy

[tlbranth]

The only things I use a torque wrench for are rod bolts, head bolts and main bearing case bolts. I have never pulled my rotor off the crank. All others are by feel. Dan

That's my philosophy too. I'd say it takes a little experience though.

[mgzych]

I'm happy to say u don't expect to be cracking the case any time soon. Just doing routine 3000 mile maintenance/tuneup. Some mentioned torque wrench for suspension... I will be pulling off the forks and changing the oil and seals, so maybe need the appropriate size/range torque wrench for that?

That digital adaptor looks interesting, but the range seems narrower than most of the click-type torque wrenches I've seen.  Not sure I understand the advantage.

Thanks for all the advice!

[Gman]

Yeah that's what I thought at first too, but the review at the link below convinced me otherwise.  It was an interesting read.

http://www.amazon.com/Alltrade-940759-Powerbuilt-Digital-Adaptor/product-reviews/B0031QPJZG

Peace,
G

[TheArchitect]

Circling back around to this one, I am in the process of getting everything together to rebuild my 750 engine.

I am also looking at torque wrenches. CDI seems to have a good reputation for the cost.

It does make sense to have 2 wrenches.

Which 2 make the most sense?

The two I am considering are:

1/4" 20-150 INCH/LBS
3/8" 5-75 FOOT/LBS

Torques from Hondman:

Engine (CB750K0-K6)
Head nuts, rod nuts, and crankshaft (case) bolts: 14.5 ft-lbs.
6mm bolts on head and crankcases: 85-95 in-lbs.
6mm bolts on cam towers: 6-7 ft-lbs., add blue Loctite.
8mm bolts on back of crankcase: 14.5 ft-lbs.

Frame
Swingarm bolt: 40-45 ft-lbs., less if arm locks up or if bolt has been used many times.
Front axle caps: 14.5 ft-lbs., tighten flush side first, to rear.
Front axle bolt: 14.5 ft-lbs., make sure the bearings are neutral and not bound, else move their positions until axle spins freely.
Rear axle bolt: 20-30 ft-lbs: same rules about the baerings as the front axle.
Drive chain adjuster bolts: 10-14 ft-lbs.
Engine bolts 8mm: 14 ft-lbs. if used many times, 18-20 ft-lbs. if new.
Engine bolts 10mm: 20-25 ft-lbs.
Engine bolts 12mm: 25-30 ft-lbs.

(Did I miss any?)

[evanphi]

From the (CB750) manual

[PeWe]

I use a small torque wrench for the important small ones easy to overtighten. 1/4" wrench 2.5-25Nm
All M6 screws 10Nm. The cam holders 10Nm, rocker shaft M5, 5Nm. Head nuts 28Nm (HD studs), case HD studs nuts got 25Nm last time as well as the other rear case bolts except the largest one behinde the sprocket that got 30Nm.

Case covers must get correct screws, too long and it can pop the inside alu falling into the engine....check that max thread lenght is around 10mm