ENGINE won't REV UP

[Street_Rod_Guy]

Hi Gang
Brand new here - just joined. always nice to have a place to do fixes yourself
Anyway here is my issue
I have a TroyBuilt Bronco riding mower
It has the 18.5 hp engine

I was cutting grass yesterday and noticed it started losing power.
So today here is what I had gone threw to try and fix it.
I put in new oil; cleaned plug; took off and cleaned out carb (it was already clean I noticed when I removed it) Disassembled everything from the gas tank to the place where carb mounts onto motor.
Put in new gas, checked lines for leaks.

Engine will start but not rev up. It does not smoke, skip, or anything like that - just seems to get revved up to about 1/2 speed, and won't rev no higher. When I put the throttle on high it seems just about 1/2 speed, and as I decrease the speed on the throttle the motor revs stays the same until I get to about 1/2 speed, then it decreases and as I lower it some more; then it will just dies. Never smokes, coughs, or sputters.

I have NO clue what is causing this, and like I said it ran fine while cutting the grass yesterday until I was just almost done. So this came up all of a sudden. Had never gave any indications of problems before, and I have used the mower off and on all winter.

SO what kind of ideas can you folks throw out that I might fix it easily.
I am guessing it won't be anything 'major' it's just trying to figure out where to start.

 

[motoman]

Sounds starved. Pull the plugs and "read" them. Tell us color and deposits- none , white, tan , brown? Fuel filter plugged? Fuel line plugged? Fuel tank cap breather hole open? Does throttle cable open and close the butterfly?

 

[Street_Rod_Guy]

Checked fuel line; it is open, filter is good, cap hole is open and throttle opens and closes butterfly...
Spark plug had no deposits, but was the normal 'brown' color. No signs or white or tan.
Cleaned the plug back it 'new' shiney state on a wire brush wheel. Looks almost like new.
Re-installed and got the same results as before.

 

[motoman]

Well, In my limited work on my Intek and reading these AC engines that run at 3000 rpm have no ignition advance, but are sensitive to timing problems such as sheared fly wheel key which could retard the timing, or a loose ignition module?? Did you hit something? You did not touch the float setting like too early cutoff of incoming gas for main jets? Others will respond I am sure.

 

[Mikel1]

Ckoke working properly? Does it rev up if you move the governor arm when running?

 

[Street_Rod_Guy]

SO far looks like you are the only one to respond LOL
In reply to your questions,.. negative to all them.
I was out in the wide open front yard just mowing along... happy as a clam
Yard is even smooth without any big bumps or anything.
I 'first' thought it was my drive belt as it is getting old and i figured I didn't have the 'speed' I was used to because of that. Then I noticed the engine was actually running slower and didn't rev up like it should of been.
I can't figure why it'd just all of a sudden only rev up to about 1/2 way without any prior problems.??

 

[ILENGINE]

When it appears to be running half throttle what position is the throttle butterfly in. I want to know if it is the full wide open position just like it would be if the throttle was at the fast position, but the engine not running.

 

[Street_Rod_Guy]

When it appears to be running half throttle what position is the throttle butterfly in. I want to know if it is the full wide open position just like it would be if the throttle was at the fast position, but the engine not running.

I'll have to take it off and look at that - didn't think to look at that.
When I had the throttle linkage and could just move the govenor arm by hand it did rev up... I could pull it as far as possible, and it seemed it 'over-rev' - (run faster that it does normally when throttle is wide open)

 

[ILENGINE]

I believe that eliminates what I was thinking. Maybe something to do with the governor spring or governor arm possibly.

 

[Mikel1]

Just checking but is the choke plate all the way open.