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Mithral

Repowered 416-H seeking tune-up/RPM guidance for tuning new engine.r trans

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Mithral

Seeking guidance for tuning a CH18S Kohler Command (1995), as replacement for a 16hp Onan (1990). 

 

This Kohler doesn't have the torque-grunt of this Onan, but it works, and is my available option. 

 

So, how best to tune the Kohler for this application?

 

1. I believe Onan and Kohler high RPM setting are both 3600?

 

2. Would it hurt the Kohler to boost that RPM to 3700-3800?   Would it really help any?

 

3. Would it hurt the Hydro Transmission to go over 3600rpm?

 

4.  I guess I could go find a slightly smaller Drive Pulley?  And what would then happen to the Trans if I can't get the proper RPMs to the Trans?

 

Now that I've figured out the mounting arrangements I can always swap in a bigger engine should I stumble upon a better option.

 

Given the difficulties of getting the Onan rebuilt now-a-days, I'm looking to go for a more modern engine with easier to find parts/service.  And I'm not inclined to do an engine rebuild myself.

 

Thanks,

- L.

 

 

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Achto
40 minutes ago, Mithral said:

1. I believe Onan and Kohler high RPM setting are both 3600?

 

2. Would it hurt the Kohler to boost that RPM to 3700-3800?   Would it really help any?

 

3. Would it hurt the Hydro Transmission to go over 3600rpm?

 

4.  I guess I could go find a slightly smaller Drive Pulley?  And what would then happen to the Trans if I can't get the proper RPMs to the Trans?

 

 

1- 3600 RPMs would be correct for both.

 

2- Boosting RPMs can generate a gain in horse power but often at a torque loss. On a dyno test, most reports will show that torque will usually peak in the upper mid range of RPMs and then decrease as the RPMs are increased from that point. HP will usually continue to increase all of the way to peak RPMs. In short, you may gain a couple of ponies by tuning up the speed of the engine but you will not gain any torque at peak RPM. 

 

3- I asked once about increasing pulley speed on a hydro to gain ground speed. It was agreed that it would work but was not recommended by most.

 

4- If you decide to increase engine speed, I would suggest doing the math on the pulley sizes to keep the hydro at the correct speed.

 

Given the fact that you are already increasing you engine size by 2HP, I would just set everything to stock size. I doubt that you will hardly notice a difference on the "seat of your pants dyno".:twocents-mytwocents:

 

Edited by Achto
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Mithral

Thank you for this most informative Response.

 

The Kohler does not pull the mower deck through tall grass with the same Grunt as the Onan did, but then I didn't really expect it to.  I'm just happy it's all working.  I'll tune everything to manufacturer specs, and keep an eye out for a larger engine.

 

If I do pulleys, I'd keep engine at manufacturer settings and simply down-size the pulley.  Issue then would be lower RPMs to the hydro, but I don't think that would be a problem?

 

Thx,

-L. 

 

3 minutes ago, Achto said:

 

Quote

 

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Mithral

Just realized I can't simply change the drive pulley.  I have the manual clutch assembly mounted.  (Which was another design/fabrication challenge).

 

BTW:  I achieved this engine swap with:

Drill Press: using a 5/6" drill, 5/8" drill.

Engine mounting adapters: 4 pieces of 1/4" x 1-1/2" bar stock, 10" long.

Clutch arm mounting bracket:  1 piece of 1/8" x 2" x 2" angle stock, 5" long.  (plus a 5/8" washer to properly space the clutch arm pivot point).

Hoist for lifting engines.

Rewired electrical harness.

Friendly welder buddy helping with exhaust/muffler arrangement.

 

Drill 2 x 5/16" holes matching the Onan mounting points in the 10" bar, along center-line of bar stock.

Drill 2 x 5/16" holes matching the Kohler mounting points in the 10" bar, also along center-line.

Placement of Kohler mounting bolts depends on where/how you want the engine to set relative to PTO placement.

Total of 4 x 5/16" holes in all 4 bar stock.

 

Now, on 2 of the bar stock, drill out the Kohler holes to 5/8" or larger.

 

Mount the first two bars under the Kohler.  And make sure you're battery ground is attached now.

(helps if you have a hoist.)

 

Place the other two bars on the Wheel Horse mounting plate aligned with Onan mounting holes.

Lower the Kohler down on top of the 1/4" bars so the bars are stacked, the mounting-bolt heads for the Kohler will sit down inside the 5/8" holes.  This way you don't have to drill into Wheel Horse mounting plate.  In my case, my preferred placement of the Kohler placed the mounting bolt patterns in very inconvenient locations with respect to the tractor frame.  So this offered a work-around.  I also needed to raise the Kohler by 1/2" so the PTO matched up with the same height as the Onan.

 

Lots of mounting bolts later, and it is solidly mounted.

 

For mounting the manual clutch, required 2 x 5/16" holes and 1 x 5/8" hole in the 2"x2" angle iron.   This requires a lot of thought, and I had to make this bracket 3 times before I got it right.

 

 

 

Edited by Mithral
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bds1984

The only concern I'd have with using that era of Kohler is the PTO clutch; the Onan has roller bearings where the Kohler most likely has bushings.  I highly doubt that the Kohler Command has the necessary crankshaft bearing to take the side/lateral load from the original clutch.  If you are using an electric clutch, you'll be fine.  

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tom2p

 

we want pictures !


 

Edited by tom2p

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tom2p
3 hours ago, Mithral said:

 

The Kohler does not pull the mower deck through tall grass with the same Grunt as the Onan did, but then I didn't really expect it to. 
 


I have two 416-H - including one I've owned for approx 20 years and now has approx 1000 hours.

 

After 20 years - still impressed and sometimes almost amazed at the way they gobble up tall and thick grass.


Can only imagine 520-H - four additional horsepower (has same bore and slightly longer stroke).

 

Edited by tom2p
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Mithral
3 hours ago, bds1984 said:

The only concern I'd have with using that era of Kohler is the PTO clutch; the Onan has roller bearings where the Kohler most likely has bushings.  I highly doubt that the Kohler Command has the necessary crankshaft bearing to take the side/lateral load from the original clutch.  If you are using an electric clutch, you'll be fine.  

 

I have not thought about this.  I do have the electric clutch from the mower I pulled this off.  I could easily install.  Thanks.

 

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Mithral
2 hours ago, tom2p said:

 

we want pictures !


 

 

Wheel Horse with Kohler CH18S.jpg

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Mithral
22 hours ago, Mithral said:

 

I have not thought about this.  I do have the electric clutch from the mower I pulled this off.  I could easily install.  Thanks.

 

 

Suggestions for mounting an electric clutch would be appreciated.

 

The old pulley has a protrusion where the manual clutch plate mounts.  This gets in the way of mounting the electric clutch up close to the drive pulley.  I barley have enough PTO shaft to mount the clutch.  And the bolt from the previous electric clutch mounting is way to short for the new application.

 

I'm not prepared to go buy another drive pulley and specialty bolts just yet, without assuring myself it will all work with the electric clutch.

 

Hmm...  not sure what to do next with this.  Other than roll the dice on the engine bearings with the manual clutch.

 

 

 

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Mithral

Update on Tuning:

(I acquired a tachometer).

 

Firstly, My starting point:

Kohler Command Pro CH18S (1995).  Taken from  a Cub Cadet 2185.

Installed in Toro Wheel Horse 416-H (1990).

 

Low Idle:

Exhaust pipe would get glowing-orange hot (way too lean).  Only adjustment for this is the low-idle needle/screw.  Set low idle to 1200rpm and turned slow idle needle out 2 and 1/2 turns as Kohler recommends.  Currently running about 2 and 3/4 turns.  Haven't found the sweet spot for low idle yet.  But it's working fine for mowing.   And the exhaust/muffler no longer glows orange after 15 minutes of mowing.

 

Note:  'Governed' low idle should be 1500-1800rpm when finished tuning.  The 1200 is ungoverned low idle

 

High Idle:

Engine taken from the Cub was set at 3400rpm High Idle.  Kohler engine webpage specs 3600rpm at WOT to achieve 18 HP.

 

Engine was slow, governor searching, even a random backfire.  Struggling on hills and in thicker-taller grass.  So I removed/cleaned carburetor and replaced worn flaking gaskets and O-rings, plus new slow-idle needle valve, etc.   With no change to the engine behavior.  Under load the Kohler was running around 2900-3100 rpm +/- going up-hill with blade engaged.  Maybe hitting 3400 on the flat if the engine could keep it's RPMs up.

 

Adjusted WOT to 3600rpm and things improved, but still had governor searching, slowness, erratic behavior.  But noticeably better.

 

Did some serious research and found that many places recommend setting these engines to 3750 rpm.  So I adjusted accordingly.   Also moved governor spring one hole farther from the governor shaft according to Kohler specs for this higher RPM.

 

Wow.  Mower runs and mows great.  No engine slowing, no governor searching, engine powers through high-wet-heavy grass just fine.   With blades engaged on the flat-slope the RPMs would sometimes hit 3600 while mowing, but mostly stayed between 3100-3400rpm.

 

Caveat:

 

Blade disengaged and full throttle forward, Engine hits 3700+ RPM.  So I have to remember to throttle back a bit to accommodate the 3600rpm Hydro specs.

 

>>>>

 

Great learning experience for me.

 

Maybe this experience will help some other newbie with their own engine swap.

 

 

 

 

Edited by Mithral
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Mithral

Update on Tuning.

 

My problem turned out to be a bad Coil.  It was running mostly on one cylinder with the second cylinder cutting in and out.

 

With both cylinders firing properly (and re-tuned to 3600 RPM specs) it runs great.

 

I'm quite pleased.

 

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Tuneup

Great to hear! I was going to suggest looking into the governor. That 18 should not have any issue and then the coil. Nice machine!

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Pullstart

Awesome stuff!  I bet 100 rpms on the transmission isn’t enough to make a difference if the engine hits 3700.  It is after all just a hydro pump and hydro motor.  

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onanparts.com
On 5/6/2020 at 4:41 PM, Mithral said:

 

 

Hmm...  not sure what to do next with this.  Other than roll the dice on the engine bearings with the manual clutch.

 

 

 

There are no "bearings" to roll the dice on with your "Modern" Kohler engine. I understand it was the available option, but a serious downgrade from the Onan. Sure hope it was free and your only cost was time/labor. Here is a look inside your "Modern" Kohler. The "Aluminum engine block" is the bearing surface for the cam and crank. Unlike the Onan, there are no replaceable bushings, bearings or sleeves etc. None! When worn or damaged, you toss the engine in the scrap pile to be recycled. When the plastic geared aluminum oil pump fails, it most likely will take out or damage those cam and crank bushing surfaces, and the crank and cam too. Since it's a disposable engine, no need to worry about getting parts for it....Pictures are worth a thousand words they say...hopefully you get plenty of use out of it before it becomes beer can material....

 

 

 

CH1.jpg

CH2.jpg

CH3.jpg

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Mithral

Yes, the Onan is definitely the better design.  I did look into having it rebuilt at a local shop, but I couldn't find anyone who really wanted to do it.  And rebuilding is currently out of my skill set.   The cost of the running Kohler was pocket change and elbow grease compared with several months of car payments needed to get the Onan running again.   When I say newer design, I really meant something I can more easily find parts for and tinker with myself.  And now that I have the mounting configurations figured out it would be quite simple to swap in another used engine if that ever needs to happen.  All in all this was a very educational and fun project for me.

 

 

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tom2p
1 hour ago, Mithral said:

Yes, the Onan is definitely the better design.  I did look into having it rebuilt at a local shop, but I couldn't find anyone who really wanted to do it.  And rebuilding is currently out of my skill set.   The cost of the running Kohler was pocket change and elbow grease compared with several months of car payments needed to get the Onan running again.   When I say newer design, I really meant something I can more easily find parts for and tinker with myself.  And now that I have the mounting configurations figured out it would be quite simple to swap in another used engine if that ever needs to happen.  All in all this was a very educational and fun project for me.

 

 


it's a shame - because there are some that can work on an Onan quickly and with little challenge 

 

including some on this site - Greentored is one recent example 

 

but to others - they treat it like they are working on rocket power 

 

5392CC50-BEC3-40B9-B96C-7B4F2DB2601E.jpeg

Edited by tom2p

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tom2p
3 hours ago, pullstart said:

Awesome stuff!  I bet 100 rpms on the transmission isn’t enough to make a difference if the engine hits 3700.  It is after all just a hydro pump and hydro motor.  


Rarely (if ever ?) run my 416-H (P216 Onan) above 3000 rpm

 

possibly a few times ?

 

more then enough power at 3000 rpm and below 

 

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onanparts.com
3 hours ago, Mithral said:

Yes, the Onan is definitely the better design.  I did look into having it rebuilt at a local shop, but I couldn't find anyone who really wanted to do it.  And rebuilding is currently out of my skill set.  

 

 

 

The skills to remove and replace an engine on your WH are basically all that's required to rebuild or repair an Onan. The only "gotcha" on the Onan's is the crank gear. It's a shrink fit and unless you have the proper adapter tool to remove it, it can be a show stopper. Otherwise a very uncomplicated engine.

 

Not wearing your shoes so no judging here! Pocket change for a running Kohler is a no brainer choice! You're happy and your pocket did not take a painful hit. It is a good engine, just not rebuidable. Wondering what was the issue with the Onan?

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Mithral

Onan was needing a complete rebuild.  Probably/[pssibly a new crank shaft.  I think I spun a bearing on the crank.  One cylinder lost compression and was 'clunking'.   Maybe someone here needs a parts machine?

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Mithral
On 5/31/2020 at 8:33 AM, pullstart said:

Awesome stuff!  I bet 100 rpms on the transmission isn’t enough to make a difference if the engine hits 3700.  It is after all just a hydro pump and hydro motor.  

 

I had the high idle set to 3700, but under load was maybe getting 3400-3600 depending.  And that was mostly on one cylinder.

 

Now with both cylinders firing and high idle at 3600, I'm getting a steady 3500 under load with no power problems.

 

Now to fix that leaking seal behind the flywheel.. argh..

 

Edited by Mithral
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