Out of interest!Did your machine still grind OK before the knocking? I just replaced a 25hp on my Carlton only because it lacked torque while grinders and turned the oil black too quickly and clogg up one of the spark plugs.It only had 650 hours but out of frustation I replaced it with a 27hp Kohler motor ($4300aust) So I wouldn't recommend you buy one in Australia and was told you will get a re-con 25hp in USA for less than $2000us!!!
you will need your spec. number off of the engine to get the correct one. If you find one from some source other than a Kohler dealer, be sure the spec. number matches. If not, there is a 90% or greater likelyhood the engine will not fit your machine without a lot of costly alterations. Any Kohler dealer will have access to new engines. You are probably looking at around $1900.00 for a new, complete engine.
Jeff
Go to www.opeengines.com I just got a 25hp kohler for my RG1625 Super JR. Best price and free shipping. Definatley match up your spec # off of your engine. Give them a call and they'll help you through it.
took the spark plugs out today one of them had hard crud all in it im going to buy some new ones tommarow get rid of the champion plugs that are in it now.