SOLVED- FZ1N 2007 bad engine rattle... Help!

[Rad]

Well, shit.
I went on a short ride, and then decided to change coolant. The procedure went well, but when I started the bike after, it sounded like there was a loose change flying inside. On top of that, it goes away when bike is upright, or tilted to the right, but when its on sidestand... https://youtube.com/shorts/utgc3JnkoxU
Any thoughts?

[Kenyun]

At a guess, I would think it is the alternator dropping apart, a common and well known problem on this model. Easily checked, drain the engine oil and remove the alternator cover to confirm.

[Rad]

At a guess, I would think it is the alternator dropping apart, a common and well known problem on this model. Easily checked, drain the engine oil and remove the alternator cover to confirm.

Alternator has been replaced right after I bought the bike two years ago. I will check it anyway.

[The Male Whale]

As it started after a coolant change I would suspect the water pump has failed or has got a foreign object in there.

[Bracechenko v2]

If it does turn out that you need a new stator rotor then let me know as I have a spare one for sale 

[Rad]

Wow, it's been a while, but the problem is finally solved.
Here's the story:
I took the bike to a" friend of a friend", who's a retired mechanic but still does odd jobs from time to time. After a day, he diagnosed loose oil pump drive chain. He installed new one, and claimed the rattle to be gone (yay!). Spoiler alert- it wasn't (boo!). For future reference- that chain is not tensioned and looks super loose from the factory. After that fiasco he threw the towel and refused to investigate further.In the meantime I was in a process of buying new house, so unfortunately didn't have time, money, or willpower to deal with my poor bike.
After dust finally settled down it was time for second round. I took her to different garage, and then they discovered it was gearbox problem Now, could sell it and make it someone's else problem, but I'd rather had a bike I knew was 100% solid. It took a while to strip the engine, but eventually we found what the issue was. One of selector forks was slightly bent, rubbing against 4th gear wheel and it was just slightly touching its neighbour- hence the rattle. Yamaha quoted cool £560 just for the wheel , but I managed to get used gearbox from ebay for just £150. After replacing damaged parts, flushing entire engine in case some debris made it through the filter, new back tyre and fresh MOT, the bike is back on the road!
The culprit

Details

Damaged wheel

Details

[Trebus]

Well done for sorting! I would never have expected it to be gearbox related.

[b1k3rdude]

The culprit

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Damaged wheel

Details

@Gnasher, what would cause wear like this? lack of oil changes or is it just that Yamaha dont have the best gear box's...?

[Gnasher]

@Gnasher, what would cause wear like this? lack of oil changes or is it just that Yamaha dont have the best gear box's...?

Neither, in my opinion.  This looks like either wheelie/clutch less change damage and/or too many drag starts and missed gears, possibly due to a poorly set and or worn clutch, which has been corrected (the clutch) before moving the bike on.  Now whether Rad has been doing the above or it was done by the previous owner, only he'll know.  But it's perfectly possible to get this sort of issue only for it to sit there for couple thousands miles before it lets go.       

[Rad]

@Gnasher, what would cause wear like this? lack of oil changes or is it just that Yamaha dont have the best gear box's...?

Neither, in my opinion.  This looks like either wheelie/clutch less change damage and/or too many drag starts and missed gears, possibly due to a poorly set and or worn clutch, which has been corrected (the clutch) before moving the bike on.  Now whether Rad has been doing the above or it was done by the previous owner, only he'll know.  But it's perfectly possible to get this sort of issue only for it to sit there for couple thousands miles before it lets go.     

Well, I asked my mechanic the same question. He said he only saw this kind of damage on bikes that were raced. Brutal gear changes with high load and high RPM are no bueno for any gearbox. It wouldn't be a problem for racing bike- they are inspected/rebuilt on regular basis, but I don't think that previous owner was that thorough:/
When I bought the bike it came with a quickshifter (I disconnected it right away), removed passenger seat and pegs... Go figure. Anyway, what happened, happened, and now I have a bike that's (hopefully) good for next couple of seasons.

[b1k3rdude]

if you replaced all the worn/damaged components, they will/should last the life of the bike.