This topic has come up a few times here ... I don't know the exact answer, just some personal experience, stories and speculation. Sorry.
Also, I'm sure every country is going to be different regards import rules, duty levied and such.
I've heard that (I think?) Argentina do not allow for the importation of "USED"
parts period. Not sure this is true or not.
In many cases parts are greased up and made to look used so as not to have to pay full duty. So, in response, some countries prohibit used parts all together.
True?
We need someone who has dealt with Uruguay and has brought stuff in on a flight. You may find answers if you dig deep enough into Uruguay Aduana rules.
Having "self made" official looking receipts would be good to have on hand in case you need them. Some countries charge OUTrageous import duty fees ...
So make up your own prices as you see fit.
A friend brought in some used BMW parts to La Paz, Baja, Mexico for his BMW
GS. He declared them and ended up having pay import duty based on his own
created receipts, which Aduana accepted. Still cost him about $100 USD for about $400 usd worth of final drive parts .... so very high price, IMO.
You may do well to show Aduana your TVIP and explain that you cannot comply with the law and remove the motorcycle from Uruguay unless you can get it running .. so you NEED these parts to comply and get the bike back on the road.
Aduana will probably say: "OK, muy bien! ... and you owe 100% tax on each item!" Or not ...
Who knows? I sure don't. You can also plead innocence or state that the parts you are bringing in are NOT for sale in Uruguay. (probably true!)
If pressed, offer your own receipts as proof of purchase. But many times it's a 100% duty fee based on value of parts.
You could also say the parts were donated FREE to you. This won't work, IMO.
The other thing I know travelers have done is to use the "Samples" story. You claim you are looking into starting a business in Uruguay and are bringing "Samples" to potential "dealers". This usually works with clothing or fashion, maybe not for hard MC parts?? Works a treat in some counties I've visited.
The key thing is to find out if "Used" parts are OK for importation. If declared as USED then the declared value could be stated VERY LOW. But as I said, some countries outlaw used parts all together. Dunno in case of Uruguay.
Keep hunting ... someone here on HUBB may have CURRENT info on this. I say current, because like everything ... the rules are constantly changing up in many countries. So good to know BEFORE your flight lands in Montevideo.
Of course most times your checked bag is not even looked at. ...
Good luck, hope you can manage this without paying too much.