I must agree with you Rupp! This holds true for any type of motor- the only time this statement may not hold true is if a power adder is brought into the equation... On a naturally aspirated motor there definitely no replacement for displacement!!!
For poorly developed engines, displacement is an easy way to add power to any two or four stroke engine. A 60 cc leaf blower usually makes more power than a 50 cc leaf blower made by the same company. A Honda stock XR 600 usually makes more power than a stock XR500. A stock 350X usually makes more power than a 250X...and so on.......
It is sad that the statement does not usually hold true for engines that are highly developed and someone just installs a stroker crank and or a big bore kit. Every week someone calls or brings in an engine that had a really good engine combination of pipe/port/carb/head/ignition and now the power is down and or it will not stay together after they went window-shopping on the net. They filled their shopping cart with snake oil and ruined a really good power package with the contents in the shopping cart. The customer reports his new big bore stoker engine has more power down in the 3000 to 5500 RPM range but does not pull has hard or rev like my old 250. I look at the mess and shake my head asking why did you do that to a real good power package?
Grandpa, Dad and Uncle Buford always said there is not replacement for displacement on those flat head ford V8s so it must also apply to the TRX 250R Hondas and all of the other high tech engines. After doing "his research": Looking at 100 other shops on the net that were selling different flavors of the same snake oil he swallowed the hook and bought a big bore piston and stroker crank. I had a friend that is the lead techs at my local Honda dealer install the kit for me. My friend followed the kit instructions. He bored the cylinder for the forged piston and then honed it to the recommended clearance of .0015” with a ball hone. He checked the welded stroker crank for trueness and he worked on it for a couple of hours and finally got true to within .003”. Then we removed the stock air box and the factory intake hose and put a K&N air filter 3” in diameter and 6” long directly on the back of the carburetor so the engine can breath with the added displacement.
It is sad but we all have probably experienced the above scenario. If you have not, you are probably still in those PAINFUL-EXPENSIVE adolescent years of learning about what to do, what not to do or who has a good recipe to build an engine to fulfill your needs.
An engine builder cannot repeatedly build a fast reliable package without first making a lot of mistakes while developing, testing and finding the right recipe (specifications and components). When a good recipe is developed and then it is followed, it will make one powerful and reliable package just like when our mom and grandmothers use a recipe that may have taken years before they "got it right". Many of the shops that sell this snake oil are often at the same experience level of building high performance engines as the customers are who at the adolescent level of just starting to get pimples.
An engine that was developed using the larger displacement during development will almost always run circles around an engine that was highly developed and then the larger displacement as added as an update.
