[RocktimusPryme]

My mower is driving me nuts. It’s a toro zero turn with the 23 HP Toro twin engine.

Long story short a couple months ago it dropped a valve mid mowing. After pulling apart the carb and other things I finally found it had a pushrod guide fail that let all sorts of bad things happen. Didn’t seem like the valve hit the piston or was otherwise damaged. Replaced the part and have been trying to limp it to winter. But now I seem to have new issues and I’m unsure if they are related. It has ran since I fixed it but not 100% right. It would pop once it got hot. The story is longer and more complicated but that’s the gist.

It had a vacuum fuel pump and it’s not sucking fuel. Replaced the pump. No help. So I checked the actual vacuum. It gets no vacuum at all cranking. If I pour some gas in the carb so it runs for a second it will pull about 5 inHg. I don’t know how much it should pull. Once it starts sucking fuel it will stay running but it’s clearly down on power and it pops (I assume lean popping)

So why wouldn’t I be making vacuum? Head gasket? I did a compression test and both cylinders are the same. But I know that’s not the end all for a head gasket, but should at least indicate the valves are sealing and the piston rings are okay. I don’t have a leak down checker. I pulled the carb apart with no kit and may have damaged a gasket or something. Should I throw a carb kit on it and see if that helps?

Local shop told me a head kit is $250. I had been planning on just doing that before spring next year just for peace of mind. But I don’t super want to do that for no reason before Christmas. I just want a Final Cut before it goes down for the year.

[poncho-mike]

Who makes the engine? Is it Kawasaki?

I can't speak to Toro models, but you mentioned the vacuum fuel pump wasn't sucking. Have you checked your fuel cap? I have a 27HP Kohlen engine on my Craftsman garden tractor. It has a vacuum operated fuel pump. As the engine sucks fuel out of the tank, air needs to get into the tank to replace the gas that the engine drew out. If the gas cap vent is stopped up, it will start to run into issues. Try loosening the cap and see what happens.

[Goatracer1]

Had a similar problem and the valves were too tight. I didn't know correct setting so I just loosened them a little and an ran fine.

[sdbob]

I fool with Kohler single cylinder engines for Cub Cadets. I'm working on my first opposing twin Kohler 20 hpMagnum. Anyway guys on Cub forum said there is a small electric fuel pump,low psi that they say will work in place of vaccum pump. I had a single cylinder kohler that the exhaust hung open. The stem was coated with carbon build up. Local cub dealer John Labuda ,a Pontiac guy,said use Kohler oil so I have been for 3 yrs no problems.

[RocktimusPryme]

Originally Posted by Goatracer1

Had a similar problem and the valves were too tight. I didn't know correct setting so I just loosened them a little and an ran fine.

Remember when I said the story was more complicated? That was one of the parts. I tried that. Popping when it got hot I originally assumed was the clearances being too tight. But it didn’t help.

And it’s Toros proprietary engine

[RocktimusPryme]

Originally Posted by sdbob

I fool with Kohler single cylinder engines for Cub Cadets. I'm working on my first opposing twin Kohler 20 hpMagnum. Anyway guys on Cub forum said there is a small electric fuel pump,low psi that they say will work in place of vaccum pump. I had a single cylinder kohler that the exhaust hung open. The stem was coated with carbon build up. Local cub dealer John Labuda ,a Pontiac guy,said use Kohler oil so I have been for 3 yrs no problems.

Considering this all started with a dropped valve I suspected valve issues. But wouldn’t that show on a compression check if something was hanging open.

[RocktimusPryme]

Originally Posted by poncho-mike

Who makes the engine? Is it Kawasaki?

I can't speak to Toro models, but you mentioned the vacuum fuel pump wasn't sucking. Have you checked your fuel cap? I have a 27HP Kohlen engine on my Craftsman garden tractor. It has a vacuum operated fuel pump. As the engine sucks fuel out of the tank, air needs to get into the tank to replace the gas that the engine drew out. If the gas cap vent is stopped up, it will start to run into issues. Try loosening the cap and see what happens.

That’s a good thought but I’m saying the port at the intake manifold actually isn’t making any vacuum while cranking. I took the pump out of the equation and checked vacuum signal at the source.

[mgarblik]

The engine on your Toro is most likely an LCT engine. Liquid Combustion Technology Inc. and CPC Certified Parts Corp. purchased the assets of Tecumseh at least 10 years ago. Both Chinese companies, they produce primarily private label engines for equipment manufacturers at a discount vs well known name brand engines like Kohler, Kawasaki, Briggs and Stratton. This doesn't help your problem however. My guess is the valves are bent slightly and not seating well enough to make power like it used to. You could remove the heads and at least check that out. Put the valves in a drill chuck and see if they are visibly bent. If they are OK, lap them in with compound and put them back together. With only 2 cylinders, you have to have good valve seal to run decent. I owned a small engine shop decades ago and old, stale gas and burned valves were among the main things we saw on a daily basis. Good luck with it.

[Jack Gifford]

Originally Posted by RocktimusPryme

... the port at the intake manifold actually isn’t making any vacuum while cranking...

I suspect that the vacuum operated pumps typically don't pull measurable vacuum while cranking. They depend on the engine starting with fuel already in the float bowl.

[VCho455]

I'm with Sarg. Sometimes it's not worth fixing.

[Sirrotica]

Check for tight valve guides, or varnish on the valve stems.

One year I parked my lawn tractor in the fall, and it ran fine; after setting all winter I went to start it up and one cylinder was dead. The valve stem had varnished up from sitting. The valve moved a little bit, but it was being held off of the seat by varnish.

One would think that removing the spring and spraying the stem with carb cleaner would dissolve the varnish. Well after about an hour of spraying and fighting with the valve I finally got the varnish off enough so that the valve would seat. In all my 5 decades of working on engines I have never seen a valve stuck that badly. I've never seen it happen since that time.

The relatively weak valve springs would never overcome how badly that varnish had that valve stuck. That was about 15 years ago, the engine ran fine until the deck finally rusted out. I still have the tractor, likely the engine is still in good shape.

Just one freak thing I ran into over the years, maybe it's not your problem, but at least something to consider looking at.

BTW, my neighbor owns a lawn care service and runs Toro commercial equipment. He told me that everyone he knew that purchased mowers with that proprietary engine has had tons of trouble with them. The new Kohlers are supposed to be problematic also. All his mowers have Kawasaki engines on them with tons of hours on them. little to no downtime. Last zero turn I bought I also went with a Kawasaki.

Good luck solving the problem......

[gtohunter]

I have a Husqvaurna 23hp, and was having problems with it starting/running. Carb was trashed from ethanol fuel, so I slapped on a chiness carb, and it still wouldn't run right, popping, smoking. took the dipstick out while running and got a shower, so I pulled the heads and there was a blown head gasket which I replaced. Finally, was not getting reliable fuel to carb, so I bought a small electric piston pump on Amazon, and that pretty much cured the fuel issue. Runs great now...like a laundry list of problems at the same time. I now keep a jug of ethanol free gas just for the mower as well.

[mgarblik]

Originally Posted by gtohunter

I have a Husqvaurna 23hp, and was having problems with it starting/running. Carb was trashed from ethanol fuel, so I slapped on a chiness carb, and it still wouldn't run right, popping, smoking. took the dipstick out while running and got a shower, so I pulled the heads and there was a blown head gasket which I replaced. Finally, was not getting reliable fuel to carb, so I bought a small electric piston pump on Amazon, and that pretty much cured the fuel issue. Runs great now...like a laundry list of problems at the same time. I now keep a jug of ethanol free gas just for the mower as well.

Ethanol free fuel is a godsend for anything with a carburetor. Small engines especially, really respond to this fuel. All the sitting time just ruins the carbs as you found out. From my experience, Stabil brand stabilizer does little to nothing for helping with this problem. A product called Ethanol Shield is far superior in this regard and I would use it if small engines sit with gas in them. I store all my seasonal small engines with a dry fuel system.

[Holeshot71]

I’m not sure if this engine is designed to have valve lash? If it is it could be that the lash is too tight. If there isn’t enough clearance, when it heats up it will keep the valve open, start popping and lose compression. HTH

[mgarblik]

Originally Posted by Holeshot71

I’m not sure if this engine is designed to have valve lash? If it is it could be that the lash is too tight. If there isn’t enough clearance, when it heats up it will keep the valve open, start popping and lose compression. HTH

Not familiar with the specific Chinese engine he is working with, but the vast majority of these engines have a screw and nut in the rocker arm for valve clearance. A generic spec. would be .008"-.012" cold. If he set the intake to .010" lash and the exhaust to a tight .012", I can almost guarantee he would be fine. Actual specs. would be better but often hard to find on the generic Chinese engines.

[RocktimusPryme]

I have messed with this a little more. I threw a new $45 ebay carb on it. It does seem to run better, but its still low on power. Specifically the right wheel seems weak going up hills. Im not positive if it solved the fuel pump issue. I did order a $10 electric pump to try. Its not popping as much with the new carb, but I also haven't really let it get hot with it.

I did a little googling and someone said it could be the drive belt, which Ive never changed. So that's a cheap something to try. The battery is also weak, so Im going to change that. I know a weak battery can cause all sorts of strange stuff. Maybe it simply wasnt spinning fast enough to pulse the fuel pump.

When I originally had the failure I found a spec for a different Toro motor that said .005 on the intake and .008 on the exhaust. So I did that, but then loosened it because it popped when it got hot. (Im still not sure if that was because of the valves or a lean condition due to fuel pressure). Afterwards I put every valve to about .010 because that's about what it was when I measured it before I ever took anything apart.

I had knee surgery last week so I haven't been able to do much. I turned 40 and my body has started to fall apart. I went out to try and look at the drive belt, but my wife caught me and yelled at me.