Electrical gremlin Kubota ZG20 ?


LawnSite Member
I have a Kubota ZG20, owned for going on 4 years, which I like quite a bit. I should mention that I bought it used, it is about 14 or 15 years old with only 250 hours. But it has developed some electrical gremlins and I’m thinking of buying a new one. Or perhaps not…

I mow 7 empty lots, 3 together, 2 together, and two separate. Standard city lots, about 1/5 acre. The ZG20 does a great job, and I’m really quite fond of it. About two years ago, the charging system quit working. It apparently needs a new stator, which requires pulling the motor, 4 hours flat rate at $125 per hour. I keep it on a float charger (also known as a battery maintainer), so no big deal.

But about 3 weeks ago it would not start. Simple diagnostics showed no spark (pull spark plug boot, hold next to block). So I loaded it on a trailer and hauled it to the Kubota dealer. Really big Kubota dealer, lots of ag equipment, big shop, very busy. It took them 10 days to get around to my mower, and it just worked. Period. Started right up. They waited two more days, starting the mower several times per day. Never a problem.

So I paid them 1 hour for their diagnostic time (no argument from me, they have to make a living) and brought it home. And it has started now 6 or 7 times, no problem. The mechanic at the dealer said it was probably something related to the safety interlocks. There is a safety interlock on the seat, on each control lever, on the parking brake – am I forgetting any? Anyway, when the engine is not running, the safety interlocks prevent the starter from engaging. Which did not happen, the starter definitely engaged. And when the engine is running, the interlocks kill the engine. Which is what I was experiencing. That is, it was ( the mechanic thinks) killing the spark instead of disabling the starter.

So my question is – could I just bypass, wire around, all of the relays that compromise the safety interlocks and (possibly) avoid any future problems of this nature? No one uses this machine but myself, so I would be the only taking risks with no safety nannies. A schematic would be helpful, and so far I haven’t been able to find one.

I would appreciate any thoughts or input on this.

Additional information: Kubota ZG20F, with Kohler CH20S engine. The date of manufacture for the engine is 2005.


LawnSite Fanatic
chesapeake, va
Yeah, you can prolly bypass all that stuff." – am I forgetting any? " why yes, yes you are :The problem is more than likely with the safety interlock module. You can prolly jump around the safeties at the module, ( I've done several Wright Standers that way ) BUT, yer gonna need a wiring diagram.
Do you know if yer motor has a smart spark ign, or just the plain magneto with kill wire ?
Kohl man. has the motor wiring diagram:

May be able to get the Kubota diagram here :

Or ask the dealers svc. mgr if he can run you off a copy of the wiring diagram.

If yer handy with a 12v test light, you can probably do it yerself...
Last edited: