Expecting too much performance from G16A?

[ez-ha]

So I have a basically stock G16A in my "zebra" it was sourced from a local scrapyard and I was able to fire it up when I got it home.
It smoked pretty bad but otherwise ran fairly well.
I pulled it out, cleaned it up, did a nice hone on the cylinder to clean it up, installed new double oversize rings to match the double oversize piston it was already fitted with.
Cleaned and lapped in the valves, new crank bearings, new headgasket, new crank seals.
Cleaned the carb thoroughly, set valves to .008 hot as per a suggestion on here about plowmans performance recommendations.
Has a non stock air filter and a Honda cycle muffler installed.
Stock primary clutch in good shape and working smoothly, RHOX secondary clutch setup supposedly goog for increased torque, stock belt over 1" wide still.
Cart has a lift kit and oversize tires but nothing too crazy.
I can tune the carb so it pulls ok at low speed but then it suffers at higher speed,
I can get tuned so it will get up to a decent speed, but then it struggles at lower speeds and on hills.
Oh and the fuel pump has been cleaned and pumps well also..
Am I expecting too much power from a 301cc engine? I feel like it should pull better than it does.
Suggestions anyone?

[Mike Mac]

The main jet is probably to small in the carb, and runs lean at higher RPM and increased load. With your modifications to the motor, it can pump more air, so you need to increase fuel imput.

Can't help with a ROX secondary clutch, but a new belt should make your car run better.

[ez-ha]

I was suspecting that as a possible cause but since I don't have any extra jets on hand I have been unable to try and tweak the size without opening the originals up some and hoping to not go too far.
Maybe I will give it a shot today if I am feeling lucky LOL

[sho305]

If setup right the motor should rev and pull no matter what you are doing. It will do so over about 5mph where CVT is fully engaged and can shift and let it rev. Of course if the motor is not running right it will be low on power, and the cvt is tuned to work with normal power, so it wont shift right with less power either it thinks you are at half throttle. You need to richen it up I bet, any time you mess with the stock airbox or exhaust on a yamaha you must rejet. I did mine with a torch tip cleaner, you can file the main out little at a time until it runs right. You can check it if you pull the choke on slightly it should run better, though it can be difficult to get it part way on while driving. If it does then its lean. I left the jet semi tight and could get it out in the cart on a G9 to work on the jet repeatedly until I had it right, then it ran fine. You can also get a jet drill set cheap and just go up one size at a time. If you must, you can torch up the jet and solder it back shut to make the hole smaller.

Imagine a lawnmower in high gear with a 10hp engine, you should get about the same at low speed with a cart. Usually 25-30mph with 22-24 tires if the governor is off.

At 1" the belt will hurt performance with a lifted cart while a stock cart will not notice much. It will want to bog at low speeds like when climbing hills. If your clutch has a kit that should help it.

[ez-ha]

Opened up the main jet some and power is way better and more consistent over the rpm range.
Pulling the choke part closed still helps some under heavy load conditions (steep hill slow speed)
Feeling more confident messing with it now with the idea of being able to "shrink" the jet back up and start over, I had not thought of that option. Thanks Mike and SHO for the tips and moral support LOL

[ez-ha]

So I reamed out the main jet a touch more and it runs like a bear..well a little bear..maybe a teddy bear..but it pulls the hills behind my house and tops out around 20-24 mph on the cell phone GPS speedo so no complaints. choke no longer has any noticeable effect on performance. Thanks again guys!

[Mike Mac]

[sho305]

Good deal! Most air cooled small engine run the best a little rich when under a big load. You should see a brown plug or at least tan. Since we load them so much they really need the fuel to do the best they can. When run on a governor on equipment they are typically not loaded so hard and spend a lot of time running high rpm at partial throttle, where you don't need as rich a mixture. Most equipment is designed to never need maximum power from the engine in normal use for longer life, better cooling, etc. But when you hit a hill with a lifted cart you need it all.