Troy Built Bronco 42" Won't turn over

[SharpAndCunning]

Hello everyone, been a member here a while, but haven't posted much. A close family friend has a 2 year old Troy built ride on mower than all of a sudden won't turn over. Apparently it ran fine a couple months ago, and when they went to start it, it turns over like 3/4 and then it can't turn over anymore. I haven't tried it by hand, but that's my first step.

All the information I have is, if they remove the spark plugs it'll turn over. I planned on bringing a compression tester over there to start, and them move from there. It's possible the valves are out of a adjustment, I know. But besides that, what would cause on of these (Briggs 19HP Intek motor) to turn over until what I am assuming is the compression stroke and then not being able to go past that?

Is there a way to test the starter, if needed?

 

[StarTech]

It can be the valves out adjustment as that disable the ACR but they are fine and there is no bump of the intake valve rocker then it time for a new camshaft and possibly a governor/oil slinger.

If it is the camshaft they have been on back order since April or May. And the after markets that I have brought are not made right either.

 

[SharpAndCunning]

It can be the valves out adjustment as that disable the ACR but they are fine and there is no bump of the intake valve rocker then it time for a new camshaft and possibly a governor/oil slinger.

If it is the camshaft they have been on back order since April or May. And the after markets that I have brought are not made right either.

So, did some investigation tonight. The starter seems to bind up on the compression stroke. I checked the battery, it was weak, so I replaced it. If the engine isn't near the compression stroke the starter has enough torque to get the engine running. I got it running and let her run for a good 10/15 minutes. All through the rev range. Runs good.

That being said, it's either a starter or the valves are significantly out of adjustment not allowing the compression release to work. I can spin the motor over by hand using the squirrel cage on the top. It's not necessarily easy, but I wouldn't say it's hard either. And if I get it just past compression and turn the key, she fires.

Is there any reason to believe this isn't the starter? Can a starter be bench tested? Just a 12V battery and tap the metal where the screw is to a ground?

If I take the two long screws out of the starter, is there anything in particular to look for? How do I test it?

 

[bertsmobile1]

Take the plug out
If the starter turns the engine over freely then it is the ACR

 

[SharpAndCunning]

Take the plug out
If the starter turns the engine over freely then it is the ACR

This is the case. Without the plug, the motor will spin freely.

It seems like this is a pretty common failure on these engines. It's possible we got lucky a couple of times and it started with the new battery.

 

[bertsmobile1]

Not a failure of the engines, a failure of the owners to do proper maintenance.
They usually come to me in desperation after having replace the battery, starter , PTO switch key switch , solenoid .then the oil & filter as if would make a difference to cranking.
I used to adjust the valve lash , charge the $ 15 for the 1/4 hour of labour and send them back out the gate.
What killed me was a crappy attitude like it was my fault they were so stupid.
So now days I tell them it will take at least a week. giver the mower a good going over, adjust the valves and send it back in 1 to 2 weeks charging them 3 hours of labour ( usual full service charge ) tell them it had me beat for ages .
When I do that they thank me greatly and choof off happy as a pig in mud

 

[StarTech]

That is debatable...As the ACR design itself is a problem area besides the valves getting out adjustment. I done replaced five 793880 camshafts this year and had to use after markets since Briggs apparently can't get them in stock. They supposed to be in stock 8/31/2021 as of today when I check they are still on back order. It is a shame to have to use the junk after market ones but customers got to get their grass cut. BUt spending 1/2 to 1 hour filing shouldn't be necessary but it is on the camshafts I installed.

 

[SharpAndCunning]

Not a failure of the engines, a failure of the owners to do proper maintenance.
They usually come to me in desperation after having replace the battery, starter , PTO switch key switch , solenoid .then the oil & filter as if would make a difference to cranking.
I used to adjust the valve lash , charge the $ 15 for the 1/4 hour of labour and send them back out the gate.
What killed me was a crappy attitude like it was my fault they were so stupid.
So now days I tell them it will take at least a week. giver the mower a good going over, adjust the valves and send it back in 1 to 2 weeks charging them 3 hours of labour ( usual full service charge ) tell them it had me beat for ages .
When I do that they thank me greatly and choof off happy as a pig in mud

So this mower is almost brand new. It's probably got 10 hours on it, and that's a stretch. Now, I could see really dirt oil maybe getting into the ACR and preventing it from operating. But in 10 hours?

That is debatable...As the ACR design itself is a problem area besides the valves getting out adjustment. I done replaced five 793880 camshafts this year and had to use after markets since Briggs apparently can't get them in stock. They supposed to be in stock 8/31/2021 as of today when I check they are still on back order. It is a shame to have to use the junk after market ones but customers got to get their grass cut. BUt spending 1/2 to 1 hour filing shouldn't be necessary but it is on the camshafts I installed.

That's concerning. Have you seen the ACR fail on a low hours mower?


So let me ask this, the spinning squirrel/dirt cage on the top of the mower, if the ACR failed, would I be able to spin the motor by hand using that?

The mower is an hour away, and I'm torn on whether to think the ACR failed or maybe there is something wrong with the starter. I didn't bench test the starter, and I should have. Except for it spinning the motor over without the plug in. But a weak starter would spin the motor over without the plug no problem..

 

[StarTech]

Yes you can spin the engine using the flywheel side it just that you must fight the compression.

A semi non invasive method of checking is to remove the rocker cover. Check that valves are to spec first and you don't see anything obiviously loose like a rocker stud then while turning the engine at two complete revs and watching the intake (the lower rocker) if the ACR is working there will a slight movement at engine reaches TDC compression stroke. If not present then ACR has broken.

And yes I have seen new camshafts to fail with less 10 hrs. A customer had two to fail in less than three months (the original one and the replacement).

 

[bertsmobile1]

So this mower is almost brand new. It's probably got 10 hours on it, and that's a stretch. Now, I could see really dirt oil maybe getting into the ACR and preventing it from operating. But in 10 hours?

10 hours in 2 years , really ?
We can only work with the information you provide
Average mow for a residential ride on used on a 1 acre block is 2 hrs a mow x 30 mows a year = 60 hours x 2 years = 120 hrs
Mowers should be serviced at the end of every season so the minimum number of services it should have had is 2
First service ( usually at some where between 10 & 30 hrs ) always includes valve lash adjustment because they can settle a bit after the first few uses .
And some times they can be wrong from the start because now that the rocker covers are siliconed on even good dealers no longer check them during pre delivery .
So sorry if it offends you but honest opinions is what comes from this little black duck and they have to be based on what the little black duck reads.

Sitting in a shed that is not properly ventilated can promote corrosion in the battery cables as well as at the ends where they bolt on , particulalry if they have not been greased or otherwise sealed form the elements by the owner.
And to be brutally honest, all new Troy Builts are throw away mowers designed to look pretty but just outlast warranttee .