By PJ White on Unrecorded Date: Edit

I have a 18HP kohler in my argo 8x8 just purchased it about 3 months ago it seems to be under powered I noticed the rear spark plug is always chalk white front plug is golden brown, I have changed plugs 3 times but they stay the same also how do I check the compression in the cylinders do I start the motor or just turn it over. What should the compression be in each cyl.Also when I disconnect the front spark plug wire the motor will not start on the rear cylinder but if I disconnect the rear it will start on the front cylinder is this normal. Any help on this will be greately appreciated.

By Al on Unrecorded Date: Edit

To check the compression, remove both spark plugs, tie the plug wires as far away from any metal as you can, screw in the compression gage in place of one of the spark plugs, and crank over the motor several times. Record the value. Repeat for the other cylinder. When you check compression, the main consideration is that the cylinders should have about the same compression as each other. Manufacturers rarely spec a compression value since temperature, cranking speed, and other variables play a large part. If they differ by more than 15-20 lbs. There is likely a problem. If one cylinder is lower, squirt a few ounces of oil in that cylinder and try it again. If the compression increases significantly, the rings are the cause, if not, it is probably the valves.
Al

By MaxRules (Brandon_price) on Unrecorded Date: Edit

PJ, many things could cause that but try this first. Take off the valve cover of the cylinder with the white spark plug. Check that the rocker arm and push rod are connected and working on the intake valve (carburetor side). It sounds like that cylinder is never getting any fuel. I have seen the Kawasaki engine in the Conquest with a bad push rod that always slipped off the rocker arm. There was no extra noise or engine trouble, just a really bad power loss.
You can't check the compression on these engines by cranking because they have automatic compression release. You can compare compression between cylinders like Al said. I bet it is the valve. Let us know.

MaxRules

By PJ White on Unrecorded Date: Edit

Well guys I checked the compression the front cyl shows 60psi and the rear 30 psi when I put oil in the rear cyl I get 60 psi I pulled the motor out of the unit yesterday Maybe it will be better to replace the motor I do not know how many hours are on it.Looking at the end of my clutch it looks like the shaft on the motor is threaded can I still buy a motor like this.They say kohler does not make the 18HP magnum anymore.If this is so what other motor can I use that my clutch will bolt too. Before doing anything I will tear the motor down to see what kind of shape it really is in.

By Alan Harper on Unrecorded Date: Edit

60 psi sounds terribly low, much less 30.
Would guess you are looking for something
closer 120 but thats doing it from memory on
Briggs engines. I read somewhere you have
to spin the engine backwards to defeat the
compression release, sounds odd and I have
never tried it though. If you forgot to lock the
throttle open that will cause low readings also.
Either way, it sounds like something is going
on in that cylinder. Rings lost their temper
maybe.
Alan

By Al on Unrecorded Date: Edit

It is probably low because of the compression release like Brandon said. But since you know the front cylinder is OK, and with the oil you get the same readings, I am sure you have a piston ring problem. Take off the Cylinder head, and check the cylinder for scratches, If you are lucky, you won't need to bore it, you can borrow a hone from Autozone to smooth out any small scratches. Check the piston for damage, and check for the rings being broken, or "stuck", they should compress freely in the grooves in the piston. I don't know any specifics about your motor, I assume it is a 1" crankshaft with a keyway, and a tapped hole in the end? I suggest getting a service manual for your motor, It will be much less expensive to repair than replace it.
Al

By PJ White on Unrecorded Date: Edit

Well guys I took my motor to a small engine shop, they tell me it is toast has a piece broke out of the case. So my next task is what am I going to replace it with they tell me it has a threaded shaft and is no longer available. If I use a Briggs I think I will need to buy a new clutch does anyone know what the Briggs model # and type# is on there 18HP.Or can anyone recommend the best way for me to go.

By David Keeso (Argomag) on Unrecorded Date: Edit

PUT IN OIL

KEEP AN EYE ON THE OIL LEVEL OF ANY ARGO MAGNUM 6X6, 8X8. AS THEY AGE, THEY TEND TO BURN THROUGH THE OIL FASTER. KEEP A CONTAINER OF OIL WITH YOU ALL THE TIME AND CHECK IT BEFORE YOU START UP EVERY TIME. LOW OIL MEANS SEIZED ENGINE.