Zincir ölçer hazırdı; madem öyle, bisiklet bakımına başladık.

Zincir ölçer is a noun phrase meaning chain measurer or chain checker/tool for measuring the chain.

• zincir = chain
• ölçer = measurer / something that measures

In Turkish, this kind of tool name is often built from a noun + a descriptive noun/agent form. Writing it as two words is normal here. You can think of it as similar to English combinations like coffee grinder or blood pressure monitor.

So zincir ölçer hazırdı means the chain-measuring tool was ready.

Hazır means ready.
Adding -dı makes it past tense:

• hazır = ready
• hazırdı = was ready

So:

• Zincir ölçer hazır. = The chain checker is ready.
• Zincir ölçer hazırdı. = The chain checker was ready.

The ending -dı / -di / -du / -dü / -tı / -ti / -tu / -tü changes according to vowel harmony and consonant voicing. Here it appears as -dı.

Madem öyle is a common expression meaning something like:

• if that’s the case
• since that’s so
• well then
• in that case

It links what came before to the next action or conclusion.

In this sentence, the logic is:

The chain checker was ready; since that was the situation, we started the bike maintenance.

A useful point: madem often introduces reasoning based on an accepted fact.

Examples:

• Madem geldin, içeri gir. = Since you’ve come, come in.
• Madem öyle, başlayalım. = In that case, let’s begin.

It is very normal Turkish and not especially old-fashioned. It can appear in both speech and writing.

Its tone depends on context:

• neutral/logical: Madem öyle, devam edelim.
• slightly emphatic: Madem öyle, neden bekliyoruz?
• sometimes argumentative: Madem öyle, niye söylemedin?

So in your sentence it sounds perfectly natural and means well, if that’s the case...

Because the verb başlamak normally takes the dative case, not the accusative.

• başlamak = to start / begin
• You start to something in Turkish: bir şeye başlamak

So:

• bakım = maintenance
• bakımına = to its maintenance / to the maintenance

That is why the sentence says:

• bisiklet bakımına başladık = we started the bike maintenance / we started working on bike maintenance

Not:

• bakımını başladık ❌

The accusative -ı / -i / -u / -ü would not fit after başlamak.

Yes:

• bisiklet = bicycle
• bakım = maintenance / care
• bakımı = the maintenance of the bicycle / bicycle maintenance
• bakımına = to the bicycle maintenance

More exactly:

• bisiklet bakımı is a noun phrase meaning bicycle maintenance
• the -sI type ending in such phrases marks the possessed element in a compound
• then the dative -a / -e is added
• because of buffer consonants and Turkish sound rules, this becomes bakımına

So the structure is roughly:

bisiklet bakım-ı-na
bicycle maintenance-its-to

You do not need to translate each part literally every time; the whole phrase simply functions as to bicycle maintenance after başlamak.

Başladık means we started.

Breakdown:

• başla- = start, begin
• -dı- = past tense
• -k = we

So:

• başladım = I started
• başladın = you started
• başladı = he/she/it started
• başladık = we started

In this sentence, the subject we is built into the verb, so Turkish does not need a separate word like biz unless you want emphasis.

Because Turkish usually leaves out subject pronouns when the verb ending already makes the subject clear.

• başladık already tells you the subject is we
• adding biz is possible, but only if you want emphasis or contrast

Compare:

• Bisiklet bakımına başladık. = We started the bike maintenance.
• Biz bisiklet bakımına başladık. = We started the bike maintenance.
  (possibly contrasting with someone else)

This omission of pronouns is very common in Turkish.

The punctuation helps show the logic and rhythm of the sentence.

• Zincir ölçer hazırdı;
  first complete idea
• madem öyle,
  connecting phrase: if that’s the case / well then
• bisiklet bakımına başladık.
  result/action

The semicolon is not required in every similar sentence, but it works well here because the first clause sets up the reason and the second clause gives the consequence.

You could also see versions like:

• Zincir ölçer hazırdı, madem öyle bisiklet bakımına başladık.
• Zincir ölçer hazırdı. Madem öyle, bisiklet bakımına başladık.

The meaning stays basically the same.

Yes. In context, hazırdı can suggest not only ready but also available / prepared / set up for use.

For a tool, hazır often means:

• ready to use
• on hand
• prepared

So Zincir ölçer hazırdı could imply:

• the tool was available
• the tool had been prepared
• everything was set for checking the chain

English may choose slightly different wording depending on context, but Turkish hazır covers all of those pretty naturally.

Yes, very normal.

Turkish often forms this kind of expression with a noun compound:

• araba bakımı = car maintenance
• cilt bakımı = skin care
• makine bakımı = machine maintenance
• bisiklet bakımı = bicycle maintenance

So bisiklet bakımına başladık is a very natural way to say that the speakers began maintenance work on the bicycle.

Yes. Turkish often allows several natural English renderings. Depending on tone and context, this sentence could come across as:

• The chain checker was ready; since that was the case, we started the bike maintenance.
• The chain tool was ready, so we started working on the bike.
• Since the chain gauge was ready, we got started on the bike maintenance.
• The chain measurer was ready; in that case, we began the bicycle maintenance.

The exact English wording can vary, but the Turkish structure and grammar remain the same.