When to use washers on bolts?

[Sci85]

Hey guys, I bought a project bike off another that was in boxes mostly. This is a xs650 based build and I am not that familiar with the model. I have lots of bolts and nuts and washers all over the place in the boxes and was wondering if there is a rule as to when to use a washer on a bolt or a nut. I have been looking at the fiche's but they don't always have enough detail to tell.

Thanks for the assist.

[Agemax]

use your instinct, or initiative, or whatever. if you think it should have a washer then use one. can never really do any harm!

[tkent02]

Lock washer, flat washer, crush washer. Most things that would hurt you if they fell off would have a lock washer. Most things that would leak get a flat washer. Seems like on a Suzuki about the only thing with no washers is the case covers, but I haven't looked closely at an XS 650 since about 1978 when I sold mine.

Might be worth spending an hour looking at someone else's XS 650 and taking notes to see what has them and what doesn't.

[Sci85]

Yeah, that was my next step tkent. I just thought there must be some engineering reason for them on some bolts/nuts but not others...

[sinkankan]

Hey guys, I bought a project bike off another that was in boxes mostly. This is a xs650 based build and I am not that familiar with the model. I have lots of bolts and nuts and washers all over the place in the boxes and was wondering if there is a rule as to when to use a washer on a bolt or a nut. I have been looking at the fiche's but they don't always have enough detail to tell.

Thanks for the assist.

The general rule of thumb is, any nut prone to vibration needs a spring washer to counterract the forces. The washer puts a "pushing" force against the threads inside and helps grip. You'll notice most side cases don't have washers because of the recessed area around the hole, this puts more direct force onto the two mating faces. The bolt is a finer thread and helps grip better than a course thread.
Most engine to frame mount bolts and nuts have a washer to help lock them up, in some cases a nylok nut to stop any vibration shaking the nut loose.
Panel bolts and screws may have a large washer to help spread the force, and not cause cracking around the metal or plastic.
Actual engine bolts usually, (and I mean there are exceptions) use a lot of torque to secure the bolt, and these are usually a higher grade and stronger bolt.
Axle bolts can come with a "castle" nut and washers, these are put a split pin though, and when viewed from the side look like the ramparts of a castle wall, and the washers are usually thicker.
When ever I have a side case off, I replace all the screw head bolts with a dome head allen key bolt in stainless. Looks better, easier to remove and tighten, and won't go rusty.
But be careful, don't subsitute engine bolts or frame with stainless, because the S/S bolts are marginally weaker, if you're looking for an appearance thing, get the bolts chromed.