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I just recently bought a 2017 HD ZT 60 and the owner's manual says to run the engine at low speed when engaging the blades. That flying in the face of everything I've always done. Plus it sounds like I threw a monkey wrench into the engine/blades. Wouldn't it be less wear & tear, and sound better, if I were to run the throttle wide open and THEN engage? Thanks all. BTW, has the slightly larger Kohler 7000 engine.

Which would create less stress on the clutch mating surfaces going from 0 to 1800 instantly or going from 0 to 3600 instantly. Does the noise stop when the blades get up to speed or do they continue making noise like there is actually something hitting something else. I am suspecting that you could be hearing belt flop when you engage.

I agree it is a heck of a load on the clutch and the 5/8 Hex belt to start up those 1/4" thick blades plus with this size deck you can throw a belt from the initial belt flopping. Several of the JD ZTR's with 60+ in decks I service it is also it is recommend to engage at a slower speed. And I can see why considering the amount belt flop I have seen at startup. Basically they are simulating a soft start feature that more expensive clutches have available that manufactures are not opting for.

As IL asked does the blade hitting sound goes away once up to speed? Also have you checked the deck for debris inside the blade area? A lot time this debris (grass, dirt, and other things) dry out and start falling down into the blade path.

I usually bump the throttle up a little off idle then engage the blades.

It is a stand off position.
Engaging the clutch at low speeds puts a lot of load on the engine but a much lower load on the deck drive system
Engaging the deck at high speed puts a lot less load on the engine but a much greater load on the deck drive system

What I have noticed is that the smaller single cylinder engined mowers tell you to engage at running speeds where as the V tins generally want to to engage at low idle.
However the big V twins generally have bigger decks as well.

I have come across cases on mowers that would kill the engine if you engaged the deck at full throttle, but would start the deck fine if engaged at idle. Has to do with the instant opening of the throttle and without an accelerator pump over loaded the fuel system and basically starved the engine of fuel with the shock load.

If you get into the compact tractor side of things with the independent electric over hydraulic pto engagement you can get some abrupt pto load starts there as well. I start the 6 foot rotary cutter behind my tractor with the engine at idle which is around 1000 rpm and the mower off of the ground. 2500 rpm is the engine speed that will give you 540 rpm pto speed. I can break the 1/2 inch grade 2 bolt that is used as a shear bolt for the pto shaft at 1500 rpm.

I've always engaged PTO implements at low engine rpm. Never could see a downside of doing it that way.

Thanks guys. No, the deck is not hitting anything. Guess I'm just used to my Cub garden tractor with a very smooth clutch. Run WOT and engage the blades - smooth take-off. Totally different with this thing. And no deck rattle. Just that nasty sudden 'impact' when engaging. Have thrown the belt once already. Guess I'l keep starting 'er at low idle. Thanks guys. BTW, great forum.

On decks that regularly throw belts , some customers have to engage the deck with the cutting height set to the middle setting so the belt run is flat.
This way the belt is less likely to jump off with the initial shock load .
On some ZTR's the belt level is the highest cutting height.

I wouldn't mind engaging the deck manually as we did in the good old days. Tried cross blading my ZTX 42 once. I felt it was to hard on the clutch. I only cross blade my 60" which has a manual engage. I'm pretty good at changing belts now.

bullet bob said:

Thanks guys. No, the deck is not hitting anything. Guess I'm just used to my Cub garden tractor with a very smooth clutch. Run WOT and engage the blades - smooth take-off. Totally different with this thing. And no deck rattle. Just that nasty sudden 'impact' when engaging. Have thrown the belt once already. Guess I'l keep starting 'er at low idle. Thanks guys. BTW, great forum.

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It is a play off between shock loading of the deck & belt and shock loading of the engine.
Check that the tension pulley arm is free to move.
IT is there to take up those sorts of shocks but they do get stuck .
JUst did a Timecutter where the pivot hole had elongated to double its length so could now swing properly.
Result was 2 broken belts two days running.

I just purchased a ztx 52 (first zero-turn) and the dealer told me to engage the blade at full throttle. He said that engaging at low throttle had more of a chance of throwing the belt.

Most owners are too lazy to do this, but I always engage the blades at the height setting where all the pulleys are in line.
On most mowers this will be the mid height point and belts that are running strait rarely throw off.

bertsmobile1 said:

Most owners aqre too lazy to do this, but I always engage the blades at the height setting where all the pulleys are in line.
On most mowers this will be the mid height point and belts that are running strait rarely throw off.

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Good point. Going to check that out.