Re: 125 Carb Swap
They are the same series TC carbs but will probably have different high speed jets. This will be because of different internal venting and expected airflow but should not affect the engine.
The whole carb will swap if you do it in pairs and will work well on either engine--just don't expect to gain any power or better idling--etc. The engine will run the same as before unless you are replacing carbs to correct a damaged or not properly functioning carb. Of course, if the 1990 has the starting enrichment valve instead of a choke--I forget what year they started that, you will need to swap that in too.
If you need gaskets, go to the auto parts store and search for a correct sized auto thermostat cover gasket--they fit and are cheaper.
