I like seeing the results. I considered replacing my pipe to get more power, but I like how quiet the factory pipe is. I hate riding in the woods listening to obnoxiously loud bikes.

 

What mods were done to the bike used on the dyno?

How many runs were performed?

Not changing anything, larger diameter head pipe will produce more power it's a known fact. All off road pipes offered are larger diameter.

 

I'm not sure that just going larger on the headpipe produces more power is a fact. Obviously you reach a point of diminishing returns and at some point the pipe is too large to scavenge effectively.

I recall reading, maybe here or on ADV, that when Bill Blue was dyno testing his 351 kit, it made the most power with the stock headtube and aftermarket slip-on, and slightly less with the powerbomb and same slip-on.

 

I agree a largerheadpipe increases power IF the header is the limiing factor. What this dyno tells me is that the head and valvetrain on this motor are the limiting factor. The next step is a valve enlargement and clean inner surfacing then retest. It would just as easily be the camshafts that are the limiting factor.

On a stock or even jetted klx, the header is NOT the limiting factor

 

if the head and valvetrain were the limiting factor then a big bore would not be nearly as effective.

cams and intake would be my my first suspects to be honest.

 

A big bore is a different issue imo. A bigger piston moves more air (more pressure?) through a finite space. A 250cc might see an improvement with enlarged exhaust valves and the 351 even more so.

I agree the cams and intake are also probable cause.

 

Or...no holes in that air box?

It's an air pump

 

Yeah thats intake system :P that and carb. Some would argue the head port is also intake syst. I run no lid i got 22hp from my 250

 

I think the stock carb is probably a bigger restriction than the airbox. Once I go pumper I might remove the airbox entirely.

 

I think it was also tested by other members that the aftermarket carbs (tm34 or tm36-68) don't improve power only throttle response