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Kohler CH20S Backfires, No Start

kdammen

LawnSite Member
Location
MN
I just picked up a Toro Dingo that's not running right. It has a Kohler Command CH20 motor in it. When trying to start it will backfire extremely loud out the exhaust and sometimes will shoot fire out the carb. I've done a deep cleaning on the carb and have new fuel and plugs. It cranks over quickly and gets good spark. I did find one bent valve pushrod. And the exhaust pipes were loose from the cylinders. I've since corrected all of this.

Any ideas where to go from here? I'm trying to pull the heads off, but that's proving to be very challenging without pulling the entire engine(which I'd rather not do since I'd have to disconnect a bunch of hydraulics).
 
OP
K

kdammen

LawnSite Member
Location
MN
That's what I was just thinking. Unfortunately I'll have to pull the engine to check it out. I think I'll pull it and do a full seal kit while I'm at it. The machine is 18 year old now.
 

Mac-s Lawn & Snow

LawnSite Senior Member
I'd try and identify the problem before removing the engine. can you see the crankshaft snout/flywheel, look for the keyways not lining up. Download a manual and see if the timing marks line up. Maybe give Tri-state Bobcat a call and see what their experience with this model is.
 

Andrew Drapper

LawnSite Member
Location
Dorset
You talk of backfire, from the exhaust and shoot fire out the carb.

backfire in the exhaust is fuel-air mix getting through the engine unburned or not fully burned and it is just burning as it is vented into the exhaust. This can be from too much fuel, running rich and just too much fuel to burn inside the cylinder.

But to be shooting fire from the carb, sound like inlet valve still open when the spark is occurring. Exhaust and carb backfire... could it be that both valves are not setting properly? But you have 160psi in each cylinder???

Intermittently sticking valves?

Got me, let me know when you have found the answer.
 
OP
K

kdammen

LawnSite Member
Location
MN
That's why a sheared flywheel key makes sense to me. If it's sparking at the wrong time it can fire up the carb. Im unable to get to the flywheel since this motor has a pulley on the flywheel side. And even when removing the pulley I'm not sure I'll have access to get to the flywheel cover bolts.
 

Andrew Drapper

LawnSite Member
Location
Dorset
That's why a sheared flywheel key makes sense to me. If it's sparking at the wrong time it can fire up the carb. Im unable to get to the flywheel since this motor has a pulley on the flywheel side. And even when removing the pulley I'm not sure I'll have access to get to the flywheel cover bolts.
But why sometimes out the carb and at other out the exhaust? That is what I would like to know.
 

BigFish

LawnSite Fanatic
Location
chesapeake, va
Something caused that pushrod to bend, right ? Mayhaps a sticking valve.
As was mentioned, ya might wanna check fer a sheared flywheel key.
Them Dingo units are a PIA to work on, I used to wrench fer a Toro dlr that had several Dingo customers...
Get ya a service man. here : https://kohlerpower.com/en/engines/manuals
 
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OP
K

kdammen

LawnSite Member
Location
MN
Good news, I believe this one is solved. I had to pull the motor to gain access to the fan cover bolts, but the flywheel key was indeed sheared. I believe a backfire is what caused the pushrod to bend. Thanks everyone for your help.
 
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