Kohler 5xi series carb

[wind77west 13]

I have a 518xi toro/wheelhorse with a Kohler ch18s engine. I have heard (internet) that the CH18 the CH20 & CH22 all have the same engine spec. Several sites state that you can make a CH 18 into a CH22 just by changing the Carb, No details are given. If you check Kohler parts site all three use the same carb part number (24 053 32). If they all have the same spec and use the same carb part number then they all should be the same HP. Can anyone shed some light on this. What am i missing.

[JoeM 7,920]

Not sure about what is different. I have heard the main jet in the carb is different and the ignition timing is different. Not confirmed. 

I have had both 20 and 22 hp and not seen any difference in power. At least for cutting grass. 

I know there is a toro spec for CH22 that has more cu in. (624 cc compared to 674 cc)  Might try a jet from that series if looking for more power. IDK Not seen the larger one in an xi tho. 

[wind77west 13]

Thanks for the reply. I also have heard about the main jet but my question how would all three hp have the same carb part number? The timing would make sense if all the the other spec are the same. I guess I will start and try to research the timing spec on each of the engines.

[kpinnc 13,647]

Many "newer" engines are like this. Bore size, crank throw and rod length, and even valves are identical between like horsepower ratings (ex 14-23hp). It takes very little to squeeze out a couple more hp, and like @JoeM said, just the jets in the carb can make all the difference. 

[Handy Don 13,328]

Another HP changer is the cam. More aggressive can alter performance. 

[wind77west 13]

Thanks for all the information. I should have known that it wasn't that cut and dry.