Toro MX4250 zero turn with Loncin 708 v-twin engine cranking slow

[dtestin]

It cranks great with plugs out. Battery is good. Seems like ACR automatic compression release is not working. Luckily it starts easily once I hold the key and get past initial compression. Any experience with this or knowledge of the ACR mechanism? I adjusted valves and did not see a "bump" on exhaust valve. Also checked electrical connections.

 

[Rivets]

I have yet to see an ACR failure on a Loncin engine, but this could be the first. What did you set the valve clearance at? Can you give us your engine model numbers and I’ll see if I can find a service manual for you. This manual is probably not for you engine, but will show you where the numbers are located. https://www.toro.com/getpub/70680

 

[dtestin]

Model 74760, I believe it is Engine: LC2P77F
Clearance (cold) (Intake) 0.004 - 0.006 in.
(0.10- 0.15 mm)
-
Clearance (cold) (Exhaust) 0.006 - 0.008 in.
(0.15 - 0.20 mm)

 

[dtestin]

Do you have a picture of the ACR so I can see how it works?

 

[Rivets]

Here is a service manual for that engine. I would start by double clicking the value clearance first, as you may have set it on the intake stroke,not the compression stroke. https://www.toro.com/getpub/117255

 

[slomo]

On 4 strokes as Rivets is getting at, there are 2 TDC strokes you can pick from.

 

[dtestin]

Valve clearances are set according to specs on compression stroke. Mower runs great but just have trouble getting it to crank. It can just barely overcome the compression if I hold the key for several seconds. Other ideas?

 

[Rivets]

Check you battery voltage while trying to start the engine. You may have a battery which is getting weak, voltage is dropping below 10 VDC, or a bad ground connection.