As mentioned in my review of Kato's 273-series 'Yakumo', one frustration was the tendency of the 8-car set (Kato 10-2000) to derail.
Snowplough?
This is definitely one possible source of problems. If you look at the photo below, it's obvious that the snowplough is very close to the track. Unitrack laid flat on a table won't be a problem, but on a scenic layout you will need to check for anything the snowploughs could catch on.
Removing the snowplough is easy enough, but do be careful to wiggle it free: it's a clip-on detailing part, and if you pull too hard, the clips will snap off. Ask me how I know!
Alternatively, you could file back the snowplough to reduce its depth. As you can see in the photo below, there's certainly enough plastic to make this possible without weakening the part too much. Only the leading cars have snowploughs. I found filing back less than 0.5 mm made enough of a difference to be worthwhile. Okay, the snowploughs are now a bit smaller than they should be, but they're still there, which is better than removing them completely!
Couplings?
The couplings do a lot of work in this set, and as the picture below shows, the set is able to turn around quite tight corners while also tilting (a feature of the real trains).
The couplings within the set, i.e., not the ones on the cab ends, work without problems. The ones at the cab ends are a bit different and need to be pulled forward before they will work. There's a black sliding cover underneath that needs to be pulled back to release the grey plastic coupler. Once that's done, the coupler will work reliably.
If you don't do that, the train will derail as soon as it hits a curve. That's because the coupler won't be able to move from side-to-side properly.
Bogies?
While doing the things listed above helped, they didn't 'fix' the train completely. It wasn't until I looked at the bogies until that happened. I noticed that the bogies aren't symmetrical front and back. On a whim, I wondered if turning them around would make any difference. Amazingly, it did! Suddenly, the train was mostly running around an oval of Unitrack without derailing.
So, I looked at the bogies to see if there was a reason why this should be. If you look at the photo below, you can see the a clip in the centre that holds onto the chassis. Towards the bottom of each bogie, a plastic rectangle that ends in a clip. This is the bit would hold the snowplough if the bogie was on a driving car.
You can also see on the bogie on the right a small light grey circle sitting inside a recess. This appears to be from the moulding process and doesn't do anything. I wondered if it was catching on something as the bogie moved. It certainly felt a bit rough. So, I took a needle file and got rid of it, as you can see on the bogie on the left. While I was at it, I used a round needle file to make sure the circular clip in the centre was nice and clean, and then a flat needle file to smooth off the top of the plastic rectangle.
I also checked that the underside of the chassis was right, too. In the next photo you can see the brass strips that press onto the electrical contacts on the top each bogie. These carry the current from the track into the passenger car. This will be used for the headlights (on the driving cars) and the internal lighting (if fitted). Curiously, the brass strips are bent on the passenger cars (left) but flat on the driving cars (right).
Anyway, once the bogies was tidied up as described above, the result was transformative!
'Yakumo' fixed?
As I write this, my Kato 273-series 'Yakumo' has been running around my scenic layout for about an hour at half-speed without any sign of trouble. It hasn't derailed once. Compared with before, this counts as a fix, and brings this Kato train into line with all my other Kato trains.













