Bicycle Mechanics - What could this be?

Hey


Quick question, I was riding my MTB recently and I noticed when I was in a certain gear (I think it is among the higher gears) I noticed that when I would pedal there would be like this mash, like this one large forceful down stroke almost like it skips, then after that its smooth. I have this suspicion that it has to do with RD adjustment, but if anyone has experienced this or knows what is going on, please any input is greatly appreciated.

Thansk

Possible causes:

1. RD misadjustment.
2. Worn chain
3. Damaged chain.
4. Worn cog
5. Sticking or frayed shift cable.
5. Poor chainline.
7. Worn chainring.
8. Generally dirty components. Lack of lube.

Could be a number of different things. Since it seems to happen in only certain gears, I would guess that it's cassette/chain related rather than freehub.

1) Worn chain and/or cogs. I once rode a chain too long. When I finally put on a new chain, it would slip on some of the more worn cogs of the cassette.

2) Broken teeth on a cog.

Hi sorry for responding so late,

So After checking my friends bike and riding alot, I noticed a couple of things...

It does this forceful downstroke more than once, if your pedailing hard it happens a good amount. It is still this really forceful downstroke that sounds like a loud crack/snap and the crank skips a little.

Also, his chain is very much so rusted, the casette/RD/Drive Train in general is really messy and needs a big clean up/lube. So my plan now is to give it a full cleaning, and then a nice lubing then see how it goes. Now if that doesnt work, I have a couple ideas. Also there are no broken teeth n the cog, that was one of the first things I checked.

Any other ideas/suggestions?

Oh, I will take some pictures tomorrow so people can see what they are looking at as far as the Drive train goes...