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Discussion Starter #1
Hi,

This is my first post, thanks in advance for any advice. I picked up a Gravely Professional 16-G yesterday, with a Kohler Magnum m18s that the previous owner pretty well destroyed. I removed the heads and cylinders today to discover both connecting rods shattered, the crankshaft journals totally gouged, the skirt on one of the cylinders broken and the camshaft in pieces. I have no intention of trying to fix this engine, so if there are parts that might help someone else, please let me know. Off-hand, I would guess the parts worth saving are the block, heads, flywheel, starter, intake maniford, carb, ignition, etc.

I'm also going to pick up an 816 tomorrow with a smooth running Onan CCKA twin, that has good compression and sounds great, until you put it into gear. It moves around OK and seems to operate as it should, except for the metallic grinding noise. The clutches don't seem to be slipping, the noise sounds more internal. (It doesn't seem to matter if the PTO is engaged or not.) All of the fluids seem full and the gaps on both clutches are around .010".

I'm brand new to Gravely, but have heard great things, especially about the 16-G tractor and the Onan CCKA engine. I don't know if they were ever offered together, but does anyone know what kind of issues I might run into if I try to put the Onan on the 16G? Both tractors are complete right now and if there isn't much benefit to the 16G over the 816, then maybe I'll concentrate on just restoring the 816 instead of swapping engines.

My understanding is that the 16G has several improvements, like the clutch system, a slightly longer frame, tighter steering, as well as probably being about 15 years newer. I'm hoping that means more available parts. The main uses would be general landscaping, creating & maintaining a garden, moving trailers around on the property, material handling of rock, dirt and some concrete I'm going to break out, some mowing and snow removal.

I'm hoping to make this a father-and-son project, as I'd much rather see my boy learn some basic mechanic, machining and welding skills than watch him play video games. I'm also planning to fabricate and install a front loader, I have most of the hydraulics already. I made one for a John Deere 318 a couple of years ago, but I had to add about 300 pounds of ballast to the rear to keep from tipping and that seemed like a lot of weight for the tires.

I really like the rear-engine design of the Gravely; it seems ideal for a small FEL and with the addition of a sub-frame, it think it could handle the stress well. I would probably go with larger tires all around to be sure the added weight isn't a problem. Even though I love the current low center-of-gravity for stability & safety, I wouldn't mind a couple of more inches of ground clearance under the rear bracket. If the new tires also resulted in a wider stance, the center of gravity shouldn't change that much.

Even after I aired up the existing tires as much as I dared to yesterday, when I winched it up 10-foot long ramps into my pickup truck, the back of the tractor still dug several inches into the ground. Of course, I may need to modify the mower deck travel & watch the PTO driveshaft angle if I increase the ground clearance more than an inch or two.

By the way, the 816 I'm looking to pick up tomorrow also has a 5' mower deck and a few other small implements. Both tractors have front PTOs and hand-clutches, I'm thinking that I would need to add or change to a foot clutch as well. Between scooping and back-dragging with a bucket, I just don't see any way around needing foot-controlled movement capability. I saw some great threads on here about converting to a heel-toe foot pedal on the right and moving the brake to the left side, or just attaching a foot peg to the hand clutch bar. I'd like to explore the ability to keep the hand clutch intact on the right and add a forward & reverse pedal mechanism on the left side to use when operating the bucket, even if the pedal didn't lock into position.

Thanks for taking the time to read this and for sharing any thoughts you might have. Even if I never got the tractor finished, it would be a great excuse to spend time with my son, but based on our previous projects, I expect that we should have a running, basic tractor in a month or two. (It seems that these tractor projects become so much fun that everything else gets put on hold and the tractor gets priority until it is running!) Then we can examine the feasibility of adding the FEL and some type of directional-control pedal set-up. I don't see the need for the additional pedals unless there is an FEL, but with a front bucket, I don't think I could do without the pedals.

I just sold a 4-wheel drive diesel tractor with a 3-point brush-hog and a front loader that was too big for our new property, so I'm pretty committed to the FEL / bucket, which led me to go with Gravely in the first place for this project. Thanks again for your time and input and be sure to let me know if you need anything off the M18S and we'll work something out. I guess I'll probably have an extra 816 tractor left over when we're done as well, take care.
 

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Sure you can put the CCKA on a G series tractor. I have put an Onan on a 16G and three other Onan engines on 8000 series tractors. The only thing that is needed is to make the gear extension match.

Once that is done and the engine bolted up, then all that is needed is electrical and fuel supply.

If that CCKA is running well, it will produce more power than the M18 ever did.
 

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There's a picture in my 816 thread where I had a CCKA temporarily installed on a 16G parts donor. The ignition system is different and Richard helped me work it out.

You will want to measure the bevel gear extension on both motors to make sure the gear seats correctly against the #1 shaft in the tranny. The spacers used on the two motors and adapter plates are very different.
 

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Discussion Starter #4 (Edited)
Richard, thanks. Yamato, thanks. I'll sleep much better tonight knowing that I'm not setting myself up for failure right from the start.

I'm surprised to hear you say that a 16.5 Onan will have more power than the Kohler. I have been very impressed with the durability of Onan twins I've seen in other applications.

Thanks again, I'm looking forward to picking up the 816 tomorrow and pulling 2 engines!
 

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Richard, thanks. Yamato, thanks. I'll sleep much better tonight knowing that I'm not setting myself up for failure right from the start.

I'm surprised to hear you say that a 16.5 Onan will have more power than the Kohler.
Not too surprising when considering 42 cu inch displacement vs. 50 cu inch displacement.

On the G series the ignition relay has to be rewired. Compare the 16G ignition relay to the 24G ignition relay to see what needs to be done. It is a pretty simple change. A ground wire is cut and a jumper wire installed if I recall correctly.

I put a 24 hp Onan on my 16G. Installing the engine was the easy part. I also changed the throttle cable as the throttle has to reach to the rear of the tractor. I made a throttle cable extension at first. I used the two cable clips, a piece of aluminum, and some throttle cable that was left over from a 5665 cable replacement. The choke cable works as-is. Your will need the same.

Put the gear that was on the M18 onto the CCKA. Straight cut gears wear in and changing the gear can lead to excessive noise. Watch your gear snap ring.
 

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Welcome :MTF_wel2:
Sounds like a neat project for you and your boy - good for you!
Post pictures as you go and I am sure that you will get all the help you need right here. :wwp:
 

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I rebadged my 16G when I put the Onan 24hp engine on it.

 

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Discussion Starter #8 (Edited)
Richard, that tractor looks awesome, great job! It might become obvious when I start tearing down the 2 tractors, but I'm not sure if I know what you mean about the ignition relay.

Are you saying that I can adapt the electronic ignition from the Kohler to somehow work on the Onan? Or are we just talking about the key-switch / solenoid / starter wiring?

I think I understand what you're saying about the crankshaft gear. If there is a snap ring, I'll make sure the gap doesn't line up with the key. In terms of the gear lash, do I use some plasti-gage and just adjust with shims, or is there the ability to position the gear on the crankshaft and eliminate shims altogether?


Thanks very much for your help.
 

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Richard, that tractor looks awesome, great job!

It might become obvious when I start tearing down the 2 tractors, but I'm not sure if I know what you mean about the ignition relay. Are you saying that I can adapt the electronic ignition from the Kohler to work on the Onan? Thanks.
Rich can speak volumes about this, but basically, assuming you leave the 16G wiring harness intact, for the CCKA ignition system you re-use the relay under the hood and re-wire it ever-so-slightly by pulling one wire and grounding one of the terminals.

Agree 100% you will want to look at the 16G wiring diagram and then compare it to the 24G wiring diagram to see the changes needed. That's how I did it.

The main reason for the change is the CCKA uses a coil and the M18 uses a magneto. You need to energize the coil on the CCKA for it to run, but on the M18, you need to ground out the magneto in order for it to stop.
 

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Discussion Starter #10
Thanks Yamato, great explanation. The ignition points & coil vs. magneto logic makes complete sense, even to me.

I'm really fortunate to find people that have already done this conversion and are willing to share their experiences, thanks again very much.
 

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In terms of the gear lash, do I use some plasti-gage and just adjust with shims, or is there the ability to position the gear on the crankshaft and eliminate shims altogether?


Thanks very much for your help.
What you want to do is to measure the distance from the adapter plate to the end of the gear on the M18. Then duplicate that measurement on the Onan.

Here is a picture of me measuring the gear extension on a Kohler 12 in preparation for a 24hp upgrade.

 

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Discussion Starter #12
Electronic ignition on Onan CCKA?

Great, now you have me thinking about converting to electronic ignition. I have to believe someone here has already tried this.

Is there a way to adapt the flywheel for some magnets and use the pick-up coil and kill switch from the Kohler? Thanks.
 

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Discussion Starter #13 (Edited)
Richard,

When you say "duplicate that measurement on the Onan", do I need to modify the crankshaft? I thought I read in a thread that the crank is stepped and there is just a key and retaining ring to hold the gear, not giving me the ability to adjust it's position. I assumed that shims were the only option at that point. Thanks.
 

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Is there a way to adapt the flywheel for some magnets and use the pick-up coil and kill switch from the Kohler?
In a word, no. There is nothing from the Kohler that will work on the Onan save for some common bolts, etc.

If you really want to convert to electronic ignition, I suggest that you use Onan's electronic ignition. It won't be a bolt on but it comes pretty close. What is needed is either replace the timing cover or machine the one you have. Then add a rotary magnet and special woodruff key, pickup, and electronic ignition coil. I have never done it but Boomer should have all the details.

Done right, you could have a dual ignition setup meaning you could choose to have either points and condenser ignition or electronic simply by moving the +12 volt wire from one coil to another, and then plug the spark plug leads into the appropriate coil.

On the early P224 engines, there is a plate covering the area where the breaker box would mount. One could add a points ignition to a P224 and have a backup ignition system should the primary fail. I have not done it but there is no reason why it would not work. Boomer would be the fellow to ask.

As far as the thrust washers go, there is a minimum thickness of thrust washer available. I think it is something like .030. Get the gear extension as close to the original as possible by mixing and matching thrust washers. You might get lucky and not have to do anything.
 

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Discussion Starter #15
Wow, that could be something to look at down the road, right after:

Picking up the 816 today in a Colorado snowstorm

Pulling both engines and swapping parts as needed

Wiring the Onan for the Gravely 16G

Higher weight-rated tires, maybe larger rims

Fabricating and installing a front end loader and bucket

Figuring out how to drive / install the pump for all the new hydraulics

Installing foot-operated directional control pedals

Please help me understand one more thing: If this is so much work, why am I always smiling so much when I'm working on a tractor project?
 

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This page shows both the relay in question and the CCKA installed on a 16G.


Make sure the noise on the 816 isn't from them pulling the motor at one time and neglecting to space the gear correctly when they re-installed it. It happened to me and put me through a very time-consuming and costly process of finding and fixing the noise.
 

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It is a good idea to record the gear extension of the original engine somewhere.
 

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The part numbers needed for a new throttle cable are:

069260 - cable assembly
075215 - grip
 

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Discussion Starter #19
Yamato,

I'm just learning how to navigate this forum, I started yesterday. I don't really understand what page you're referring to that shows the relay. How do I link to it?

Is there a fairly simple way to determine if the Onan is installed with too much / too little gear lash? Thanks.
 
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