Just put a Saito 1.50 in my new H9 Cessna 182 (95''). I'm in the process of breaking in the engine and it runs great. Problem is: I can't get rpm's any higher past half throttle. The engine sounds great up to about half throttle but if I push the stick further it sounds like the engine is really straining to get higher but just can't. My very best guess is that it can't get enough air into the cowl that it needs to breath freely. I have not tried to run without cowl yet, but I'll try that next. I've got this plane looking so scale that I'd hate to cut hole in the cowl but I may have to. Anyone else have this problem? Is it gasping for air or do I have a carb problem?

not getting enough air in the cowl to satify the carb is nearly impossible. you could overheat with a cowl sealed too well, but that isn't your problem. how about the prop size? what you are describing sounds exactly like a prop that is too large for the engine, especially for break in.

Sounds like you are just not getting enough fuel to the engine. Is the tank up close to the firewall, and roughly centered on the carb? Are you sure the hose is not pinched somewhere? Unless you have a restriction there's no reason the engine wouldn't pull rpm. Provided the HS needle is open far enough.

I also see this at least contributing to the problem:

Until you have the engine pretty well run in you have to leave the LS needle fairly rich, if you have it turned in too far the engine will go lean about 1/2 way open on the throttle.

Your best thing will be to pull it out and bench run it for at least a half hour or so, then with the needles more properly adjusted you can finish the job on the plane.

If you just have to do it in frame, open the HS needle about five turns and see if it will run up to speed, then you can start leaning it out.

Bill.

First off, Smokingcrater could be right about the prop...I'm using a Master Airscrew 16x8. I should be using more like 15x6 now that it's mentioned. I'll try that.
As far as the needle settings; I've not touched the low speed setting, only adjusting high speed as it idles perfect right out of the box. Yes I am running it rich on HS and leaning slightly as I go along. Tank is placed properly and nothing wrong with fuel line. I remember having this problem with Saito .72 in my Pizaz a few years ago. A new engine will overheat due to new parts rubbing together causing power loss, sometimes even shut down. .72 was not quite this bad but after break in it 's the most solid running engine I have.
I did forget to mention that my 1.50 does at best a fair job at full throttle when it's warmed up, but after I've run it for a while the problem occurs. I think I'll give this engine a fair chance to break in before I say it has a real problem. Thanks guys for the advice.