Ne streĉu la ŝraŭbingon ĝis mi kontrolos la selon.

The ending -u is the Esperanto volitive ending. It is used for commands, requests, instructions, wishes, and similar meanings.

So:

• streĉi = to tighten
• streĉu = tighten / should tighten / let ... tighten

In this sentence, Ne streĉu means don’t tighten.

Because the subject is not stated, it is understood as you. Esperanto often leaves out vi in commands.

Esperanto makes negative commands very simply:

• Ne
  • -u verb

So:

• Streĉu! = Tighten!
• Ne streĉu! = Don’t tighten!

There is no separate word like English don’t. The negation is just ne.

The -n ending marks the direct object in Esperanto.

Here:

• streĉu la ŝraŭbingon = tighten the screw-part / threaded part
  → la ŝraŭbingon is the object of streĉu
• mi kontrolos la selon = I will check the saddle/seat
  → la selon is the object of kontrolos

So both nouns take -n because each one is receiving the action of its own verb.

Ĝis means until.

It sets a time limit:

• Ne streĉu ... ĝis ... = Don’t tighten ... until ...

So the idea is that the tightening should not happen before the checking. The checking comes first; only after that may the tightening happen.

This is a very common question for English speakers.

In Esperanto, it is normal to use the future tense here if the checking is genuinely in the future:

• mi kontrolos = I will check

English usually avoids will after until, but Esperanto does not have to copy that English pattern.

So:

• English: Don’t tighten it until I check the saddle
• Esperanto: Ne streĉu ... ĝis mi kontrolos la selon

That is natural Esperanto.

Not in this sentence if you mean a simple future action.

• kontrolos = will check
• kontrolu = check! / should check / let me check

Here the speaker is not giving a command inside the ĝis clause. They are simply saying that they themselves will perform the checking later. So kontrolos is the right form.

Normally, no. Esperanto usually needs an explicit subject in a finite clause.

Since kontrolos does not show person by itself, mi is needed to make it clear who will check:

• mi kontrolos = I will check

In the main clause, the subject can be omitted because commands commonly leave out vi:

• (Vi) ne streĉu = (You) don’t tighten

But in the subordinate clause, mi must be stated.

It is a compound word:

• ŝraŭb- = screw
• -ingo = holder, socket, sheath, receiving part
• -n = direct object

So ŝraŭbingo is a noun built from smaller meaningful parts. Esperanto does this very often.

A useful thing to remember is that in Esperanto compounds, the last main element usually gives the basic category and core idea. So ŝraŭbingo is a kind of ingo, connected with a ŝraŭbo.

La is the Esperanto definite article, meaning the.

So:

• la ŝraŭbingon = the screw-part / the threaded socket
• la selon = the saddle

It is used because the speaker has specific, identifiable things in mind.

Also, Esperanto has only one article form:

• no separate a/an
• no changes for gender
• no changes for case

So even though the nouns take -n, the article stays la.

Not completely. Esperanto word order is fairly flexible because the -n ending shows which noun is the object.

The neutral order here is very natural:

• Ne streĉu la ŝraŭbingon ĝis mi kontrolos la selon.

But for emphasis, other orders are possible, for example:

• La ŝraŭbingon ne streĉu ĝis mi kontrolos la selon.

That would emphasize the screw-part.

Even so, the original version is the most straightforward and normal one.

It can cover both ideas depending on context: making something taut, tight, or tense.

With something like a screw or fastening part, the natural meaning is to tighten.

So in this sentence, streĉu should be understood in the practical mechanical sense, not as physically stretching the object.