problem with oil pan bolts

[p_s]

'85 GS550ES.

The torque spec for the 15 oil pan bolts is 10 ft lbs.
Twice tonight I was halfway through torqueing them all (which takes a long time since the gasket is thick), and a bolt snapped between the bolt head and the crankcase. It was easy to get the bolts out with vise grips and I have (used) spares, but what gives? Should I order high-grade stainless stuff instead?

I noticed two of the sump bolts in this engine were different, probably higher grade, that some PO had put in, and the sump bolts in my other engine were more than finger tight, but definitely less than 10 ft lbs tight. The threads in the block looked fine.

[psyguy]

for the bolts that keep the engine covers in place i only go "snug" with a hand spanner and if the gasket leaks i tighten the problem area a bit more

it is difficult to get an accurate torque-wrench for such low spec unless you want to spend a lot of money

stainless steel bolts are a good idea. the hardness of the bolts doesnt matter as they are bolted into aluminium that is anyway a softer material
your bolt snapped probably only because it is very old and has been through the heat/cold cycle a "few" times

[TheCafeKid]

My GS manuals all state that ALL cover bolts are only 7ft/lbs. That would put them right in line with Trippivots statement. And, unless you are using a inch/lbs wrench, 10 ft/lbs puts it on the lower side of the wrenches rating, and I can say from experience, it is somewhat difficult to feel/hear that click, as its nearly non-existant. If you feel like you are torquing it down too much, you probably are. Harbor Freight sells a couple of different "click" type wrenches that do in/lbs for cheap. In fact, ALOT of the bolts on these bikes are fairly light in the torque department. Made me realize how badly I was over torquing everything when I finally bought one.

[Nessism]

Just looked up the torque recommendation in my 850 manual and they have a general call-out of 5.0 - 7.5 ft-lbs for 6mm bolts.

[twr1776]

I agree with psyguy, when I replaced my pan from the dreaded PO helicoil drain plug fix I was more concerned with the proper tightening sequence than cranking them down. I just went around the pan twice snugging and the third time gave them a little extra and it has not leaked. Less is more on these smaller bolts.

[p_s]

I'm using a 0-250 in lbs Proto beam-type torque wrench. I bought it used. New it goes for $200 or so. 10 ft lbs is right in the middle of the scale.

I have 3 manuals that say the same thing about most 6 mm bolts, but not these.

[Nessism]

Suzuki used different grades of bolts depending on the application on the bike. The lower grade have a 4 imprinted on the head and the stronger ones have 7. The 4's and the bolts without a mark have a max torque of 5.0 ft-lbs, and the 7's can take 7.5 ft-lbs. Not sure what these grades equate to but thought like sharing.

[p_s]

Suzuki used different grades of bolts depending on the application on the bike. The lower grade have a 4 imprinted on the head and the stronger ones have 7. The 4's and the bolts without a mark have a max torque of 5.0 ft-lbs, and the 7's can take 7.5 ft-lbs. Not sure what these grades equate to but thought like sharing.

They all had 7's. Interesting that they only take 7.5 ft lbs. I couldn't find in my manual what the "7" meant.

I should also mention that all the bolts would happily torque to about 8 ft lbs. But going from there it is just compressing the gasket. I never got any of the bolts to 10 ft lbs even after several rotations before one would snap. I guess I'll leave em snug.

All the threads look fine as well.

[psyguy]

I never got any of the bolts to 10 ft lbs even after several rotations before one would snap.

i think you might be stripping the threads in the cranckcase - a typical symptom is when you can keep rotating the bolt but not getting increased resistance

I couldn't find in my manual what the "7" meant.

this is a typical system used by japanese manufactures (cars included)
the number is used to indicate the torque setting only in conjuction with the bolt size
as such, the number itself doesnt follow any ISO standard measure of either the bolt tensile strength or the required torque setting

[p_s]

I downloaded the manual for the same year TSCC 16-valve GS750ES. It specced 7 ft lbs. So did the manual for the older GS1000s.

So I think the official service manual just got it wrong and the other two manuals copied the bad number. The threads weren't stripped in the crankcase and everything is happily torqued to 7 ft lbs now.

I also put all the valves back in with new valve seals and adjusted the tappets. This bike is getting ever closer to being back on the road.

[DanTheMan]

Good job, Paul!!!!!!!!! So I'll see you in Fennimore????

[p_s]

Good job, Paul!!!!!!!!! So I'll see you in Fennimore????

Sure hope so. I'm still waiting on the title for the other frame--I might go anyways. (I don't know if you remember, but my frame was twisted on one of the down tubes that goes under the engine, so I decide while I'm at it to swap frames.)