Help. Need new motor

[Fibylion]

When i was 15 me and my dad went halves on a 86 (i think?) argo 6x6 with a kohler kt17qs motor in it. Most fun machine ive ever had going slow. Loved it a lot lol, ended up buying a winch and a light bar for it (and various other stuff) for it, but never installed it... why you may ask? Well i'm pretty certain the motor is done. it always ran perfectly, but one day i was just going up and down our road, and it just shut off. we took a stab in the dark and replaced the mechanical fuel pump, still no start. Okay, can get it to sorta fire on choke, and it will run on ether (I know i know ether is bad, this was the only time i ever used it on this motor) so we are figuring fuel problems ect, anyways after messing around with cleaning the already pretty clean carb, i had the bright idea to do a compression test, which gave one cylinder about 80 psi, and the other something like 20. we did take it hunting one time and my dad managed to half sink the thing so maybe it got water in the motor, but we checked it all out and it ran fine after that so im not sure, anyways i took the motor apart something like 4 times now in my shop class and i dont understand how it has next to no compression, i lapped all the valves, put new crosshatching in the cylinders, did this and that, ive got a manual giving me all the specs and the lower rings are like 2 thou '' out of spec, but would that seriously make it go down that much?? anyways put it back together, havn't done a compression test but it feels like it has literally nothing now, and its spitting everything into the crank case so i guess its rings. I'm not messing around with rebuilding this really old warn out motor (kits are also stupid expensive for them...) so we are thinking about going down the route of re powering the argo, heres my actual question, does anyone know of an engine that will fit in this thing, ideally using the clutch off the old motor?? i was looking into some cheap chinese honda knock offs but i'm really not sure what will go in it. A little diesel would be cool too but i feel like that would be a pain. thanks for the help.

[Fibylion]

No suggestions?? What would you guys do, rebuild it or new motor?

[KevinW]

I can't suggest a motor replacement but I would look at the piston and cylinder,
If they look good, I'd be putting new rings in it.
If the piston and/or the cylinder is bad then I would be replacing that as well.

[curtisbyrne]

you can replace it with a predator engine.ive seen some 20hp kohler commands in older argos as well.you can get anything to fit its just up to you and your father if you can customize the engine to fit.i would first look at some briggs and starttons or kohlers.

[dirtdobber]

What would you guys do, rebuild it or new motor?

I would first figure out what's wrong with the existing motor. You told us that it went from running to fine to dead in a matter of moments - which could be a number of things including fuel, ignition (including bad wiring), immediate loss of compression through blown head gaskets, cracks/holes in pistons/cylinders, or a valve/timing problem. You have been into the motor several times so surely you went back with new head gaskets (and clean mating surfaces) and inspected the heads, pistons and cylinder walls for cracks or other damage and found none. You lapped the valves so if a valve were burned or failing to seat surely you would have noticed that. I assume you put it all back together with the crank and cam in proper time. I assume the cam lobes and what ever other mechanisms that open and close the valves are all functioning and not damaged. The only thing left is the rings, piston, and cylinder bore unless there is some other mechanism, such as a compression release system, to fail. You mentioned you honed the cylinders, and that the rings were only .002 out of spec, but I'm not sure what spec you are referring to. IF the rings and cylinders are worn, compression will reduce over time and oil consumption will increase, but it shouldn't just all of a sudden quit running.

Make sure you have a good compression gauge and are checking the compression properly. Pull both spark plugs and with the gauge connected whirl it over with the starter and a good strong battery. If the compression still checks low, then I have an idea that might indicate if it is a ring problem (I've never done this - just a thought). Add about 2 or 3 tablespoons of 90 weight gear oil to each cylinder through the spark plug hole. Roll the motor over several times to distribute the gear oil and redo the compression test. If the rings are the problem, the gear oil may serve to help "seal" around the rings and provide a little higher compression reading.

If still low compression and you are confident the rings/pistons/cylinders are good check the timing (easier said than done!). I don't know the best way to do this other than perhaps pulling a head so you can watch the the valves and piston as they travel.

[ARGOJIM]

Is it possible you have aligned the ring gaps ( rings should sit about 1/2-1/3 out of line) and or not adjusted the valves after opening it up? New head gaskets? on properly?

[Fibylion]

Pistons and cylinders look good, one piston has some dents in it (looks like something was bouncing around in the chamber for a few strokes) but nothing is scored or anything, i just dont know if i should decide to re ring it and end up not being the problem

[Fibylion]

you can replace it with a predator engine.ive seen some 20hp kohler commands in older argos as well.you can get anything to fit its just up to you and your father if you can customize the engine to fit.i would first look at some briggs and starttons or kohlers.

Yeah we were looking at the predator engine, just weren't sure if the primary clutch would mate to it or not, we can definitely fabricate some motor mounts or whatever, so thanks for the suggestions

[Fibylion]

I would first figure out what's wrong with the existing motor. You told us that it went from running to fine to dead in a matter of moments - which could be a number of things including fuel, ignition (including bad wiring), immediate loss of compression through blown head gaskets, cracks/holes in pistons/cylinders, or a valve/timing problem. You have been into the motor several times so surely you went back with new head gaskets (and clean mating surfaces) and inspected the heads, pistons and cylinder walls for cracks or other damage and found none. You lapped the valves so if a valve were burned or failing to seat surely you would have noticed that. I assume you put it all back together with the crank and cam in proper time. I assume the cam lobes and what ever other mechanisms that open and close the valves are all functioning and not damaged. The only thing left is the rings, piston, and cylinder bore unless there is some other mechanism, such as a compression release system, to fail. You mentioned you honed the cylinders, and that the rings were only .002 out of spec, but I'm not sure what spec you are referring to. IF the rings and cylinders are worn, compression will reduce over time and oil consumption will increase, but it shouldn't just all of a sudden quit running.

Make sure you have a good compression gauge and are checking the compression properly. Pull both spark plugs and with the gauge connected whirl it over with the starter and a good strong battery. If the compression still checks low, then I have an idea that might indicate if it is a ring problem (I've never done this - just a thought). Add about 2 or 3 tablespoons of 90 weight gear oil to each cylinder through the spark plug hole. Roll the motor over several times to distribute the gear oil and redo the compression test. If the rings are the problem, the gear oil may serve to help "seal" around the rings and provide a little higher compression reading.

If still low compression and you are confident the rings/pistons/cylinders are good check the timing (easier said than done!). I don't know the best way to do this other than perhaps pulling a head so you can watch the the valves and piston as they travel.

The motor does have spark and cranks and all that stuff. it does get fuel. Head gaskets are not blown, but no i did not replace them but they look good. pistons/cylinders all look good, and now that i lapped the valves they look good too (had some pitting in a couple of them before) no cracks in anything, and i never went into the engine block on the motor, just took the cylinders off about a thousand times. i did look at the camshaft though in the hole and all the lobes look good ect. Its electric start so it does not have a compression release system, and in the manual i have it gives a maximum ring end gap that you can have, it is 2 thousands of an inch above that maximum ring end gap, but i cant see how the compression would go down that much, i have a snowmobile with a shredded piston that makes more compression than this motor does. and ive never noticed having to add oil to it. compression was checked with multiple gauges, all stating the same result. i have heard of the oil trick, and i didn't end up doing it when the motor was still in the argo because i figured the problem would be obvious. I will do it sometime next week though.

[Fibylion]

Is it possible you have aligned the ring gaps ( rings should sit about 1/2-1/3 out of line) and or not adjusted the valves after opening it up? New head gaskets? on properly?

What do you mean by aligning the ring gaps? like have them all in a line? if so when i installed them i set the ring end gaps 90 dregrees apart from eachother, hoping i would gain come compression from that. And this motor does not have adjustable valves, unfortunately. Thats what i thought the problem could have been, until i opened it up and realized you cant adjust them.

[dirtdobber]

Yes, he means having them all in a line. If you separated them by 90 degrees that would solve the problem ArgoJim was talking about. I question the wisdom of recycling the head gaskets....not sure how well that works. .002 extra end gap on the rings wouldn't account for the drastic loss in compression. The engine was running before with those rings and that extra ring gap (unless you really took out a lot of material when honing the cylinders!!). When you lapped the valves, did you inspect the mating surfaces of each valve and its seat?

[Fibylion]

Yes, he means having them all in a line. If you separated them by 90 degrees that would solve the problem ArgoJim was talking about. I question the wisdom of recycling the head gaskets....not sure how well that works. .002 extra end gap on the rings wouldn't account for the drastic loss in compression. The engine was running before with those rings and that extra ring gap (unless you really took out a lot of material when honing the cylinders!!). When you lapped the valves, did you inspect the mating surfaces of each valve and its seat?

I just re used the head gaskets to just see what was wrong with the motor first, they both look great, and once I going the problem I wanted to take it all apart again and replace every gasket and wear part in the motor. I didn't hone it much, and I checked the ring end Gap after I honed the cylinders. Each valve you can now see the mating surface, and it's all nice and shiny. In our shop we have a valve grinder, so I wanted to grind them all down but we don't have the tool to grind the seats too (kinda defeats the purpose of having the valve grinder if you ask me) I'm still not convinced that the valves are totally sealed though, isn't there some way you can put compressed air in em and see if they leak? How would I go about doing that? Thanks.

[plott hound]

a leak down test will tell you whats going on.put the piston on the compression stroke them preasurize the cylinder through the spark plug hole.see if theres air coming out the exhaust or the carb.

[Fibylion]

a leak down test will tell you whats going on.put the piston on the compression stroke them preasurize the cylinder through the spark plug hole.see if theres air coming out the exhaust or the carb.

Okay thanks, I'll try this, sometime this week. I've got a pile of work to do on my truck first

[eddieb1965]

Pf they are non adjustable valves,you need to get a measurement and grind the stems to the proper spec.The valves are probably not closeing fully...