Ketju ja poljin narisevat, joten toin pyörän korjaukseen.

Because the subject is plural in meaning: ketju ja poljin = the chain and the pedal.

In Finnish, when two singular nouns are joined by ja (and), the verb is normally plural:

• ketju narisee = the chain squeaks
• poljin narisee = the pedal squeaks
• ketju ja poljin narisevat = the chain and the pedal squeak

So narisevat is the 3rd person plural form of narista (to squeak / creak).

Because the sentence is talking about one pedal, not both pedals.

Finnish uses singular and plural much like English here:

• poljin = pedal
• polkimet = pedals

So ketju ja poljin means the chain and the pedal. If both pedals were meant, you could say ketju ja polkimet.

Narista means something like to squeak, creak, or make a squeaking noise.

It is often used for mechanical parts, doors, floors, bikes, and other things that make a dry rubbing sound.

Examples:

• Ovi narisee. = The door creaks.
• Pyörä narisee. = The bike squeaks / creaks.

In this sentence, narisevat means are squeaking or squeak.

Joten means so, therefore, or which is why.

It links the first clause to the result:

• Ketju ja poljin narisevat = The chain and the pedal squeak
• joten toin pyörän korjaukseen = so I brought the bike in for repair

It is a very natural way to express consequence.

Rough comparison:

• joten = so / therefore
• siksi = for that reason / therefore
• siis = so / thus / in other words

In this sentence, joten is a straightforward connector meaning so.

This is a very common question.

Finnish distinguishes between:

• tuoda = to bring
• viedä = to take

The choice often depends on the point of view.

• toin = I brought
• vein = I took

If the speaker is speaking from the place where the bike was brought, or treats that destination as the relevant point, tuoda is natural.

So:

• Toin pyörän korjaukseen. = I brought the bike in for repair.
• Vein pyörän korjaukseen. = I took the bike in for repair.

In many situations, both can be possible, but tuoda suggests motion toward the relevant location, while viedä suggests motion away from where the speaker is.

Toin is the past tense of tuoda (to bring).

Forms:

• minä tuon = I bring
• minä toin = I brought

So toin pyörän korjaukseen means I brought the bike in for repair.

Because the sentence describes:

1. a current or general situation: the chain and the pedal squeak / are squeaking
2. a past action taken because of that situation: so I brought the bike in for repair

Finnish allows this kind of tense combination naturally, just as English does in sentences like:

• The chain and pedal are squeaking, so I brought the bike in for repair.

The present tense in the first clause can describe the problem as something still true now.

Because Finnish often leaves out subject pronouns when they are clear from the verb ending.

Here, toin already tells you the subject is I:

• toin = I brought

So (minä) toin pyörän korjaukseen is fine, and usually minä is omitted unless you want emphasis or contrast.

Here pyörän is the object of the verb toin.

With a completed action like I brought the bike, Finnish often uses the total object, and in the singular that often looks like the genitive form:

• pyörä = bike
• pyörän = bike (object form here)

So:

• Toin pyörän. = I brought the bike.

This form shows the action is directed at the whole bike as a completed event.

Functionally, it is the total object, but its form is the same as the genitive singular.

This is one of those things that can be confusing for learners.

In practice, in a sentence like this:

• Toin pyörän korjaukseen

you should understand pyörän as the object form used for a complete, finished action. Traditional grammar discussions may talk about genitive-form object or accusative function, but for a learner the important point is:

• pyörä = basic form
• pyörän = whole bike as the completed object

Korjaukseen means for repair or more literally into repair.

It comes from the noun:

• korjaus = repair

The form korjaukseen is the illative case, which often means into, to, or for the purpose of entering/undergoing something.

So:

• pyörä korjauksessa = the bike is being repaired / is in repair
• viedä pyörä korjaukseen = to take the bike for repair

This is a very common Finnish expression.

Because Finnish noun stems often change when case endings are added.

The basic form is:

• korjaus = repair

The illative singular is:

• korjaukseen

This happens because nouns ending in -us / -ys often form related cases from a changed stem:

• korjaus
• stem: korjaukse-
• illative: korjaukseen

You do not have to derive it from scratch every time at first; it is often easiest to learn it as a pattern.

Similar examples:

• rakennus → rakennukseen = into the building
• vastaus → vastaukseen = into the answer / for the answer

Because Finnish often uses a noun phrase to express purpose in situations like this.

• tuoda pyörä korjaukseen = bring the bike for repair
• viedä auto huoltoon = take the car for service

This is very idiomatic Finnish.

A verb form like korjattavaksi or another structure may also be possible in some contexts, but korjaukseen is simple and natural.

So this sentence uses a common everyday pattern: [bring/take something] + [noun in illative]

It is the illative case.

The illative often answers the question mihin? = into where? / to where?

Examples:

• kouluun = to school
• kauppaan = to the store
• korjaukseen = for repair / into repair

Here the idea is that the bike is being taken into the state/process of repair.

Yes, literally that is close, but in natural English you would usually say:

• for repair
• in for repair
• to be repaired

So toin pyörän korjaukseen is most naturally:

• I brought the bike in for repair.
• I brought the bike for repair.

Yes, Finnish word order is fairly flexible, though different orders can change emphasis.

The given sentence is neutral and natural:

• Ketju ja poljin narisevat, joten toin pyörän korjaukseen.

You could also see:

• Toin pyörän korjaukseen, რადგან ketju ja poljin narisevat.

But that changes the flow and emphasis.

In general, Finnish often puts known information earlier and new or important information later, but the standard order here is very natural for everyday speech and writing.

Usually yes, in everyday Finnish pyörä commonly means bike or bicycle.

Literally, it can also mean wheel, depending on context, but in a sentence like this, especially with chain and pedal, it clearly means bicycle.

Examples:

• polkupyörä = bicycle
• pyörä = bike / bicycle (common short form)

Yes, it is natural and idiomatic.

A Finnish speaker would understand it easily as something like:

• The chain and pedal are squeaking, so I brought the bike in for repair.

Everything in it is normal:

• the plural verb with a compound subject
• joten for so
• toin as past tense
• pyörän as the total object
• korjaukseen as a common purpose expression

Yes. Finnish, like English, often mentions only the relevant parts causing the problem.

So ketju ja poljin narisevat does not mean those are the only parts on the bike; it just means those are the parts making noise.

This is completely normal.

Here are the main forms:

• ketju = chain
• ja = and
• poljin = pedal
• narista = to squeak / creak
• joten = so / therefore
• tuoda = to bring
• pyörä = bike / bicycle
• korjaus = repair

Sentence forms:

• ketju
• poljin
• narisevat ← from narista
• toin ← from tuoda
• pyörän ← from pyörä
• korjaukseen ← from korjaus

One possible version would be:

• Ketju ja poljin narisivat, joten toin pyörän korjaukseen.
  = The chain and the pedal were squeaking, so I brought the bike in for repair.

Or if the repair is already completed:

• Ketju ja poljin narisivat, joten vein pyörän korjattavaksi. Nyt se on korjattu.
  = The chain and the pedal were squeaking, so I took the bike to be repaired. Now it has been repaired.

This helps show how the tense in the original sentence keeps the squeaking relevant to the present.