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Hi I Have Troy Bilt Walk Behind with a 9hp Briggs and Stratton motor. It start easy runs on tick over but will not rev at all when under load. I will rev ok until the blades start cutting then drops to tick-over.
The throttle is opening fully
The governor is not closing it up.
New Air filter but removing it makes no difference.
Taking of the tank filler cap makes no difference, nor blowing into the tank to pressurize it
Plenty of fuel, tap open and ok
fuel is getting to the carb in a large enough volume
No air leaks that I can see
Plug colour is ok not weak or blackened
Choke is opening ok and chokes the engine if engaged while running.
The tappets show a gap when checked after warm-up.
Bearings in grass cutter are ok
Year before last I changed the coil plug and ht cap after it had starting problems. Turned out to be the carb was flooding the engine with petrol because I was not shutting the fuel of when parked.
As the present problem started at the end of last year, and I had had fuel/float problems the year before, I purchased a new (pattern) carb and had fitted this when I started cutting this year but the problem has remained. It runs ok but only without load even with the throttle fully open. Walking at 1/2 a mph is taking a long time to cut the lawns
Any ideas please?

https://www.jackssmallengines.com/jacks-parts-lookup/model-list/troy-bilt/wc33xp

post year & model & serial numbers

https://www.briggsandstratton.com/e...ualSearch.html?searchrequested=215802-0223-e1

see page 21 illustrated parts list items 121 & 121A carburetor overhaul kits.

Engine: Briggs&Stratton 9.01 ohv
Model: 215802-0223 e1
Type Code: 30225ZA

So are you saying that the throttle is sitting in the full wide open position when running but the rpm's are low. If so then pull the valve cover back off and turn the engine over by hand and watch the valves open and close, Are both valves opening the same distance. Have seen the cam lobes where to an almost round shape on the camshaft cause a self speed limiting issue.

Have seen the cam lobes where to an almost round shape on the camshaft cause a self speed limiting issue.

Think you are spot on, missed that when I checked the tappets clearance. the inlet valve is hardly moving. Once the hardened surface of the cam is worn out they soon wear away. I took all the tappet clearance out and it runs a little better but will not last long. I can now mow the lawn at 3/4mph. May be time to look at getting a ride on, have been looking for an excuse to convince the wife. She say says I need the exercise cause I'm old (and fat) Thank you for your help.

ILENGINE said:

So are you saying that the throttle is sitting in the full wide open position when running but the rpm's are low. If so then pull the valve cover back off and turn the engine over by hand and watch the valves open and close, Are both valves opening the same distance. Have seen the cam lobes where to an almost round shape on the camshaft cause a self speed limiting issue.

Click to expand...

good call i saw that on a Briggs 17 HP