M18 Starting Problems

[jchamberlin]

I got a great deal on a used Magnum 18 that had been removed from an 1864 Cub Cadet tractor. The motor was originally equipped with and external oil filter, but since the filter was not installed when I looked at the motor (5 hours from my house), I wasn't able to start it before I made my purchase.

After I was able to procure an oil filter & hoses from a fellow forum member, and after I installed it in my CCC 782 circa 1982, I am discovering that it may need a bit more than a little MMO to bring it back to life.

Symptoms:

Motor turns over, but doesn't sound "even" and while it "fires," the motor refuses to run. Instead, I get alternating puffs of black smoke out the exhaust and "popping" backfires through the carburetor.

Possible Causes:
!Ignition: Spark tester reveals steady spark, I put in new plugs, so I'm thinking ignition is not an issue.

!Carburetor: I'm getting identical results on either starting fluid or gasoline, so I think that an issue with the carburetor is eliminated.

?Valve Sticking: Could an intake valve be stuck or bent or something?

?Timing: Could the timing be off?

I can't decide whether to pull the heads off to check out the valves, pull the engine out of the tractor so I can get the flywheel off to check the key on the crank, or pull the breathers off to check out the valves before possibly pulling the heads --or do all three.

I would appreciate any input before I tear into this thing, especially things to check that will determine whether I'm looking at a full rebuild or whether the motor can be resuscitated by paying attention to a few key components.

 

[mgonitzke]

Let's see...it's an M18, the timing is not adjustable, so that's out. I think I'd remove the breather covers and observe the valve stems as you crank it over and check the valve lash. It sounds like the lash is too tight on the intake valve, it's not closing all the way, or otherwise not sealing.

 

[jchamberlin]

Matt: Thanks for posting a response. I'm hoping to give it a go tomorrow, here's to hoping it is only a rusted/stuck valve stem!

 

[jstertz]

Jeremiah--Did you figure out what was wrong with your M18 yet?

 

[jchamberlin]

Joshua, No, but thanks for asking. Its a long story, but the lawn needed mowing and I had to get a deck working to get it done --took me all day.

I'll keep you posted.

 

[jstertz]

Jeremiah--It is always frustrating to have to fix something before you can do what you must do like cutting the grass, clearing snow, etc. I have been following your b belt- v-belt thread with interest. Just curious on that M18 since you know I have an M20 in my Cubbie refurbish. One of these days I'll have that up and running. I'm very interested in finding out whats up with yours.

 

[jchamberlin]

Joshua: Stay tuned, I hope to finally spend some time on the M18 this weekend. I still have to get both a 50A deck and a 44A deck working and cut my neighbor's grass. His John Deere is down (for about the third time this season) and it gives me great pleasure to "help him out."

 

[jstertz]

Jeremiah--that is a neighborly thing to do! I'm watching this post with continued interest! Good luck on the project.

 

[jchamberlin]

Joshua: I got the neighbor's grass mowed with my 149-powered 50A deck after 8:00 PM yesterday (in the dark with one headlight), since there were many patches of knee-high grass, it took a long time to cut it, and my 14 HP motor felt the strain, but powered on through (at reduced speed). I don't think I'll allow him to let it grow that high again. The 50A seems to do OK if you keep within the standard mowing limits by cutting only 1/3 of the grass blade's height --with sharp blades.

I should finally be set to take some pics of the M18 tomorrow. (I hope I don't jinx it by posting this.) I've got the 50A working as well as it's going to this season; I've got the 44A positioned for completion by the middle of next week; I've robbed a re-buildable spindle off the 42" deck (new last year, < 10 hrs service) for the 44A and returned the 42" deck to service (by using a "good-enough" water-pump-style spindle from the 44A).

Meanwhile, the 44C deck is staged for installation on the 782, awaiting only the restoration of power via the CCC M18. Then my tractor will finally be un-confuguliated!

I really hope that by this time tomorrow you're looking at pictures of the M18 which should tell the tale of why it won't run. I'm hoping it is is just a stuck valve; but at this point any diagnosis is better than not knowing.

Worst case: I'll have to disassemble both motors in order to move the crank into a known good motor. Of course, if I have to open both of them up, a rebuild of at least one of them is likely.

Here's to hoping it is only a stuck valve.

 

[jchamberlin]

Update: I took Matt's advice and removed the breather covers on both cylinders, the front (near the PTO) and the rear (near the flywheel). I checked the valve lash, and there was no clearance on the intake valve on the front cylinder, so I focused on the front cylinder, opened the head and pulled the valve.

The valve looked OK, so I proceeded to file the stem and re-install. I also checked out the seat, found some rust, and cleaned it out.

I then lapped the intake valve in:

After a break (those keepers get on my nerves), I came back, buttoned it up, and tried to start it --No Go! I tried spraying some starter fluid in the carb inlet, but got nothing. I played with the choke a little bit, and got some weak combustion sounds from at least one side --but no start!

At least it wasn't back-firing through the carburetor! I guess the valve adjustment took care of that symptom --thanks, Matt.

I couldn't tell if it was cranking correctly, but it sounded more like what I'm used to, only faster. The starter kicks out a lot, but it still turns over.

I didn't know what to do next, and then I thought --compression test!

Both cylinders were within a couple of lbs of each other --both at or near 90 psi.

I put the battery on a trickle charger for the night. Maybe with a few more cranks and it will turn over. If it doesn't, I'm going into the carburetor next. Spark wasn't the strongest, but it will be last on the list.

I would hate it if I have to rob 1/2 of one motor to get the other going; it kind of defeats the purpose.

 

[jstertz]

Jeremiah,
Thanks for the update and the pictures. It looks like you had a little less carbon than my M20 had on the cylinder heads. I've cleaned that up and installed new head gaskets, etc. It sounds like it has decent compression, that is nearly the same as mine. I haven't checked it since I cleaned everything up but I'll do that because I'm interested to see if that changed it at all. It is confusing why your engine won't fire. If you have spark and compression, fuel delivery seems to be the only other logical problem. Have you tried priming the carb with a little fuel? Many times that will get things rolling. My M20 was dry for a while and when I got it set up, I put a thimble full of fuel in the carb and it fired right away. After that it would start nearly immediately. Now on my 149, the carb was so full of gunk after sitting for 10 years, it needed a carb rebuild to run. Everything was nasty! GOOD LUCK

 

[jdiederichs]

Jeremiah:

I don't want to bring it up now that the engine is installed, but that flywheel key is a real possibility after all.

 

[jchamberlin]

Jim: I'm thinking the same thing. The motor should run on starter fluid or carb cleaner or a thimble-full of gas, etc. even if the carb is toast. At least that is how every other engine I've tried to diagnose acted.

It probably wouldn't hurt to pull the flywheel if only to check the state of the magnets and the air gap of the magneto. When I tested the spark earlier, I used a B&S diagnostic tool. Since I had no one to sit on the seat to crank it, I had to do it myself and I couldn't get a good look at the quality of the spark, I could only tell that some was present.

Then too, the flywheel key could be damaged slightly and throwing the timing off. I know that a deformed key will throw a B&S motor off; I read somewhere on this or another forum that Kohler motors weren't affected in the same manner as B&S motors by the "key factor," but I don't know why they would not be.

So, proceeding along a logical path, the issues at the flywheel should be eliminated before investigating the fuel system.

By-the-way, I have an electrical fuel pump on the tractor, so I know the carb is getting fuel.

 

[nbextermueller]

Jeremiah,

Both my 782 (kt17) and 2072 (mag20) are hard to fire with "low" batteries. They both spin fast but just won't fire off. If I put the jump box on it when that happens they always roar to life. It seems to be an amperage problem and not a voltage problem. Those big starters are stealing all the amperage to turn it over and not much is making it to the coil which is a dual post and is firing both sides also (not helping out).

Both tractors now have 340CCA batteries vs. the little 150CCA that was in it. I have no more starting problems.

 

[jchamberlin]

Nic, I trust you're not giving me false hope!

 

[jchamberlin]

Update: Trickle charge on the battery didn't help. The motor still doesn't sound quite right when I crank it; it seemed to fire through the carb again, although not as badly. I used a good shot of starter fluid and no choke on the initial crank; full and 1/2 choke on successive cranks.

Battery is rated at 375 CA, 300 CCA, but may not be in the best of shape. It is at least two years old. It didn't have enough umpf to start when I got back from 2 weeks vacation a month ago, even though all the cells were full. After charging for 12 hours and sitting for another 24 hours, it still jumped up to 3 Amps on the charger when I hooked it up again just before trying it, although it quickly returned to zero; after cranking the motor 3-5 times, the rpms started to drop, so I threw the battery back on the charger and it jumped up to 6 Amps initially.

So I'm still going ahead with plans to pull the flywheel for all the reasons I stated in my previous post and see what I find before tackling the carburetor.

Thanks for the feedback Joshua, Jim, and Nic; I'll keep you posted on developments.

 

[nbextermueller]

Before pulling the motor, try jumping it with your truck if you can get it close to it. If that doesn't give it enough juice to fire, it's not the battery.

 

[jchamberlin]

Nic, I'll keep your suggestion in mind, right now the 782/M18 is in the back of the shed. I have to wait for clear weather in order to get the Model 149 out of the way (sitting in the yard). Driving the truck into the back yard risks ruts and septic field damage. But, hey, I could carry the battery from the truck back to the shed, right?

 

[jdiederichs]

Try jumping it with the 149 then instead. Next try running a jumper cable from the battery (-) directly to the engine bare metal. The batt ground to the frame, and the frame to the engine, may be suspect due to corrosion.

By running your ground cable direct to the engine (by use of the jumper cable black from the batt (-) to the engine you will eliminate another possible fault.

Might be enough to fire it(?)

 

[jchamberlin]

Jim, Nic: the weather is going to clear soon. I'm going to pull the engine, if for no other reason than I need to replace the cast piece at the end of the driveshaft as well as the part with swivel bearing in it (after only 1 year!). Then I'm going to do what I should have done in the first place, and what I intended to do before the deck-to-PTO belt issues interfered --get the engine working on the bench (floor, actually) BEFORE I attempt to put it back into the tractor.

Thanks for all the suggestions, I'll keep you posted.