Hi,
In order to tighten an old headset I have two big spanners which are very heavy.
Is there a way to tighten the headset, if it becomes loose, on the road without the spanners?
A hackish way will do ok, because we will be in France, Spain and Italy, but still we need to be able to ride with a loose headset 100km, until we find a place to tighten it.

Thanks,
Kfir

Adjust and tighten the headset(s) properly before your trip. Use grease and get the nuts well tightened against each other. You shouldn't have a problem. In the unlikely event it loosens up on you, you can stop at any auto mechanic shop and ask to borrow a wrench, channel locks, whatever to get you to the next bike shop. It takes some trial and error, but it can be done with one wrench on just the top nut.

I wouldn't carry any headset tools on a tour -- too heavy and bulky, and most likely unnecessary.

I guess I didn't close it well, the first time, and it got loose. I did close it again. Hopefully it is now closed good.
The problem is that I don't have the feeling how much to tighten.

Thanks for your reply,
Kfir

If the headset was installed properly, with enough gap between the top nut and the fork, it should not loosen with proper torque on the nut. Headsets tend to loosen when there is not enough of that gap, even if you tighten very well.

You can check it yourself or have a trusted mechanic check it for you.

If done properly, you should have no worries about it on the road.

check these out.
https://www.abundantadventures.com/quads.html#HEADLOCK