thrown away ... really ?

I am looking for the opinion of that guy with a lot of expertise gained in a motorcycle shop.
The repair manual calls for quite a few bolts to be ditched after one time use,
example: mounting bolts on the front brake calipers.
a) what's the rational behind this ?
b) have you done it in your shop, and if you didn't, did this ever cause problems ?

Some bolts are made to stretch for some reason and they lose their uniformity getting longer and skinnier in the middle

I have not been good about replacing the front brake caliper bolts and have not had a problem. For some reason I did change them a week or so ago when I had the wheel off.

Torque to yield bolts lose their strength once they stretch. They are designed to be a onetime use as tightening them again to the yield point of the bolt runs a high risk of breaking the bolt. This is very common for cylinder head bolts, however I never heard of caliper bolt being a torque to yield.

There are also a lot of "single use" bolts just because they come factory coated with a thread locker coating already applied and nothing to do with stretching.

I had to take the engine bolts out of my Triumph Daytona to mount frame sliders. The bolts were reusable but the nuts were one time use only. There was a fair bit of friction to get them torqued up.

Thanks for your input, all.
Wouldn't a bolt of the stretching kind have a special area (not where the thread is) for stretching. If it changes shape where the thread is ... uhhu ...
What I mean is, wouldn't it be possible to see and identify such kind of bolt ?
@tev : have the feeling that's why the caliper bolts are "one time", at least that would make sense to me.

Good, correct info above. There are certain single-use bolts, such as connecting rod bolts that should be replaced.
But caliper and disc bolts, like Tev says, have a locking agent applied to the threads from the factory. Honda, with it's typical overabundance of caution and fear of litigation, cannot rely on a mechanic or owner to re-apply it. I would simply apply Picture and reuse and re-torque.

per google:

Bolts that stretch under use are called torque-to-yield (TTY) fasteners or stretch bolts. They are tightened past their elastic limit, causing them to permanently deform and elongate. TTY bolts should never be reused because they become weakened and can't apply the proper clamp load. They must also be replaced if they are loosened or removed, even slightly.
Stretch bolts are designed to stretch when assembled to provide a strong and reliable clamp. They are especially useful in critical assemblies where loose bolts can cause serious problems

pekingduck_imp said:

Good, correct info above. There are certain single-use bolts, such as connecting rod bolts that should be replaced.
But caliper and disc bolts, like Tev says, have a locking agent applied to the threads from the factory. Honda, with it's typical overabundance of caution and fear of litigation, cannot rely on a mechanic or owner to re-apply it. I would simply apply Picture and reuse and re-torque.

Click to expand...

Same advice here and the internet search also agreed with us.

Out of curiosity i got my torque wrench out and checked the values;
Top right bolt: 26nm to undo and 33nm to put the bolt back on it's mark and similar for the others.
the bolts were just rotated until i could feel movement and placed back on the mark so the
loctite is still servicable.



Over tightening would worry me more because the calipers are aluminum....

So replace with blue loctite is fine, something else i do is to rotate the calipers in the direction of
the brake action just before doing the bolts up, this makes sure that they are always aligned perfectly on the disks and mark the bolts with a yellow crc marker pen along with some other bolts for a quick visual check, thanks Gecko for another good question, hope we cleared this one up.

Thread locker around the brakes might be "special" for high temperatures. So there's that.

IMHO: If the bolt we are talking about is for a floating caliper, it's not stretchd ot fatigued as an engine head bolt would. Just make sure the shank is clean and without marks or scratches that could hinder caliper to float, and make sure that proper thread locker is used. If we are talking about the caliper carrier bolts, the heat they receive is much less, so they don't suffer cyclic loading. But my bike has radial calipers (RS) so I don't know exaclty how the floating caliper assembly is done.

I agree with pekingduck when he mentions "Honda's typical overabundance of caution and fear of litigation". I would trust resuing those bolts, but I'd be checking periodically that they are not coming loose (just use a marker and check they don't rotate). Maybe use loctite 272, or some other high-temp threadlocker (although it might be dificult to remove in the future...)

Another - related - question. When yo check your sparks after some 10,000 miles and they look as good as mine always seem to ... I put them back in with the initial torque. But of course the washer got compressed when the spark was first installed, and the torque should be increased (right ?)
Of course I wouldn't do this 5,6,7 times or more to the same spark. Now, just buying new washers for the sparks (IF you could find them) isn't worth it. So what do you do ? Not check the sparks, not re-use them, or increase the torque ?

(( user manual p.67 doesn't give torques, it quotes the old style 1/5 turn after it seats, etc. but to be honest that Honda procedure doesn't make a lot sense to me, not for old sparks, not for new. ))

I never check torque on a spark plug. Just snug them up.

The ferret_imp said:

I never check torque on a spark plug. Just snug them up.

Click to expand...

Don't wonna sound smart-a...
As long as you ride low rpms and temps (which most of us do on the CB1100 I guess), that can't cause any problems. But at 8000 rpm and high exhaust temps this could cause ... something when the gasket isn't tight enough ?
Or am I overly cautious ?

I once owned a Suzuki T250 two-stroke. Great bike. One dark night heading out with some mates on a camping trip, I got to the top of a hill and there was an almighty bang. A spark plug had blown clean out of the engine.

A mate towed me to our destination. There were no motorcycle shops, but I was referred to a small-engine repair man who wrapped a piece of asbestos rope around the thread and reinstalled it. Worked well until I could have it properly repaired.

Cormanus_imp said:

I once owned a Suzuki T250 two-stroke. Great bike. One dark night heading out with some mates on a camping trip, I got to the top of a hill and there was an almighty bang. A spark plug had blown clean out of the engine.

A mate towed me to our destination. There were no motorcycle shops, but I was referred to a small-engine repair man who wrapped a piece of asbestos rope around the thread and reinstalled it. Worked well until I could have it properly repaired.

Click to expand...

AMAZING Corm, how come you are up that early in the morning ?
Did you know that the Wright brother's early engines didn't have or need sparks at all ?

The Gecko_imp said:

The ferret_imp said:

I never check torque on a spark plug. Just snug them up.

Click to expand...

Don't wonna sound smart-a...
As long as you ride low rpms and temps (which most of us do on the CB1100 I guess), that can't cause any problems. But at 8000 rpm and high exhaust temps this could cause ... something when the gasket isn't tight enough ?
Or am I overly cautious ?

Click to expand...

Don't wonna sound smart-a...
As long as you ride low rpms and temps (which most of us do on the CB1100 I guess), that can't cause any problems. But at 8000 rpm and high exhaust temps this could cause ... something when the gasket isn't tight enough ?
Or am I overly cautious ?
Guess that is a legitimate concern Gecko. There is a torque spec for every nut and bolt on a motorcycle. Then you can get into the argument for dry thread torque vs wet thread torque lol. I also don't torque to spec oil drain plugs, or oil filters or axle nuts, or handlebar clamps etc. I doubt most people do. I do own a torque wrench but rarely use it. I think if you were working on internal engine parts, cranks, cam journals, engine cases etc it would be wise to follow torque specs. I worked in motorcycle shops for 17 years, never have seen a mechanic use a torque wrench on a spark plug. Not saying no one does, but I've never seen it.

I dont want to give you bad advice, so ignore it if you choose and follow your own conscience