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2020/05/16 18:44:15

spaceman

Engine won't rev up as high on full throttle Kohler CH20OS Toro Groundmaster 120

Its 1 Kohler CH20OS 624CC spec 64555, serial 2726715917. Toro Groundmaster 120
The throttle is pushed up to full throttle but it doesn't seem to be as high as it was. If I push on the
Govenor arm it revs up. There seems to some adjustment that is out of wack. I replaced the spring going to that
arm in the picture. I have a new fuel pump and filter and spark plugs. It seems to startup fine and run fine but
just not able to get more RPMs in the full throttle position??????

When I kick the blades in they don't come up to full speed like they use to a few weeks ago. Something is acting
strange here. If I push on the Gov arm where that spring is in the picture the rpms come way up like they use to.

What do you think is wrong here???????????????? Hope someone can help.

35 comments Leave a comment

Roy

With the trottle up as far as it will go the lever attached to the other end of the cable should be against the stop. If not loosen the clamp and pull the cable then tighten the clamp.

2020/05/16 19:09:53

spaceman

I checked the cable in full throttle position and tightened it. Im adjusting this screw and locknut in the third picture and it seems to be making a difference.
I wonder is there adjustments that can be made to the carburetor is there a carburetor on this engine twin Vee that can be adjusted. It might have been awhile since its been adjusted?????

I found a service manual online and that screw with locknut is the highspeed adjustment screw looks like from
what I read.

2020/05/17 13:06:11

Roy

If the engine is running smoothly there should be no reason to mess with the mixture screws.

2020/05/17 15:31:51

spaceman

Yes run good. The high speed adjustment screw might need adjusting. I found that in the service manual online.
https://www.manualslib.com/manual/700336/Kohler-Ch18-745.html?page=44#manual

I turned it some and it seems to be helping. Will play with it later today.

2020/05/17 16:12:19

spaceman

Well I adjusted everything but when I kick in the blades the engine doesn't seem to have enough power
to run them up to speed they use to run at. The turn but not at the high speed they should run at.
What could be causing this???????????????????
Has me puzzled.
Im not sure whats going on.

2020/05/17 18:41:31

Roy

Ground the spark to each cylinder. I supect one is dead.

2020/05/17 18:45:40

spaceman

What do you mean ground spark to each cylinder. What can be dead.. How do I do that?

I have worked and replaced many things on this mower but this is a new one for me.

Thanks for your help,, this is something new for me on this mower I haven't run into before. Im a newbie

2020/05/17 19:12:01

Roy

Remove the spark plug wire to one cylinder at a time then stick a screwdriver into the terminal and lay the shank against a metal surface. If nothing changes that cylinder is not producing power. If the engine quits the other cylinder is not working.

2020/05/17 20:31:17

spaceman

Ok will do the spark plug thing tomorrow and see what I find. Thankyou very much for this help.

Jack

2020/05/17 21:32:41

spaceman

I haven't tried the screwdriver into the spark plug terminal yet. I just wonder why do that and not just pull
the sparkplug wire while engine is running and see if engine quits if Im looking maybe for a bad Ignition Coil on one of the cylinders.
Im sure there is a reason for the screwdriver placed against some metal while the engine is running.

Just wonder about that.

2020/05/18 12:22:08

Roy

You will figure that out when you pick yourself off the floor and catch your breath.

The screwdriver next to some metal will tell you if the ignition on that side is working.

2020/05/18 12:47:10

AVB

But it is a good feeling to to get hit 12-15Kv. Getting hit 35Kv is even a better feeling.

2020/05/18 12:53:36

spaceman

Ok understand. Oh I forgot I had this spark plug tester in the tool box. I will try it first.
If its a coil its not going to be fun getting to the flywheel, its behind part of the Frame on this Groundmaster 120. I might have to take some of the side frame apart just to get to it.
Will check the front spark plug first since its easy to get to. The back one I have pull the gas tank up a little and
take a rubber cover off over a access hole to get to the spark plug. There is a metal wall there..
I installed new plugs just a few days ago when I thought they might be the problem but didn't think about the
ignition coil. I bet that is what it is. Will find out tomorrow.

Thanks guys for the help.

2020/05/18 17:26:48

spaceman

Well don't seem to have power to the front plug. If I unplug the front plug the mower will still run.
If I unplug the back plug and plug in the front plug it will not run. I guess the front plug is not getting
in power. The ignition coil for it must be bad.
The question is how do I get to the coil under the cowling on the Toro GroundMaster 120. Has anyone replaced
a coil on one of these. There is not much room between the side and the cowling to pull out.

2020/05/21 19:04:17

Roy

Try changing the plugs first, use new ones.

2020/05/21 20:48:16

Roy

You may have to remove the engine to access the coils.

2020/05/21 20:51:04

spaceman

I replaced the plugs with new ones and just to double check this front one I just changed it with another new
one and the same thing. So looks like the coil for the front plug has gone out.
My problem is how to get to the coil, to replace it. Yikes
I wish I knew someone that has replaced one before and how they did it.

2020/05/21 21:59:29

AVB

As Roy hinted at you may need remove the engine just to get to the coils. I got a few riders here like the old shaft drive Cub Cadets where the engine has to partially come out to get to coils. Glad they don't fail very often but one of the reason the 2T engine crane here though I need a gantry type instead, my back just won't let me do this heavy lifting anymore.

Yes 2T is overkill but I need it for auto engines and lifting of ZTRs when pulling transaxles assemblies. The Z925A is especially a pain as both has to come as one assembly.

2020/05/22 07:52:14

spaceman

I use to own a 2T engine lift and used it on my tractor when I split it to install a new clutch. I don't have it anymore.
I do have a heavy duty Gorrila ladder I can adjust to different heights and it could straddle over
the top of the engine and I could use a Come along hanging from 4 x4 post lying across two of the steps at the right height for the come along to hang from. I think would work.
There two lifting brackets on the top of the motor to lift it.
Might take a picture of the ladder and come along and the 4x4 post across two of the steps.

2020/05/22 12:04:01

spaceman

Well Tested it again on the front cylinder with plug tester with clear plastic window to see spark and
this time it was darker in the garage and can see a glow in the test. So I guess there is a spark. If the spark is
strong enough I don't know if that can matter. Might be something else. Maybe I would have to have a compression checker to check cylinder. I have a guy that looked at it to maybe buy it and he has a compression checker. He didn't see the plug tester glow but just sent him a picture of it so he know there seems to be a spark.
Maybe a valve stuck or something. Looks more then I want to get into so I guess I will just sell it to someone that knows how to fix stuff like this.

2020/05/26 20:03:26

AVB

Just a note about those line neon spark testers. THey can give a positive indication. Here what member of a forum I manage said.

I just worked on a friend's Kawasaki twin. It was running on right cylinder only. Left cylinder had spark with tester inline to the installed plug. Put in new plug. Nothing changed.Even shocked me when applying plastic coated alligator clip for balance test. Grounding tester directly produced spark. But when I used clip to ground the uninstalled plug there was no spark across plug gap. Same thing on right side showed spark. I didn't have my compression gauge so we even pulled valve cover to ensure valve action was ok. So then we swapped the coils. Guess what. Left side had spark. Right side did not. My conclusion is bad coil. (Tests with kill wires off) That's with grounded uninstalled plugs. So coil is not strong enough to jump the gap. Bit puzzling since inline tester showed spark when attached to installed plug. An internally shorted plug would do that but our final testing was with new plugs on both sides. I know coil may spark to ground but not jump a gap under compression. I expect same goes for jumping gap with no compression. Just puzzled that tester showed spark IIRC on a new plug.

2020/05/27 10:41:27

spaceman

That is what I was wondering about if the spark is not strong enough to jump the gap on the plug, even if you see it
in the plug testing tube. So it still might be the coil that is not making a strong enough current to jump the gap on the Plug.

2020/05/27 11:07:09

AVB

That is why we use an open air tester set @ a gap that 15 KV to jump the gap. It is use to test only the ignition coil and not with the spark inline.

2020/05/27 12:05:44

spaceman

Interesting I haven't see one of these testing tools. Cool That would prove the coil is weak if it would not jump the gap.
I did a search and the price for the tester is not bad.

2020/05/27 20:18:58

AVB

spaceman
Interesting I haven't see one of these testing tools. Cool That would prove the coil is weak if it would not jump the gap.
I did a search and the price for the tester is not bad.

Just Google PN 19368.

2020/05/27 20:32:19

spaceman

Well I got this testing tool for checking the coil and it seems to show there is no spark on the front coil. Its shows
one on the back coil cylinder. Its easy to see the spark in the gap on this testing tool.
So if I want to replace coil looks like I will have to lift the motor up. There are bolts on the bottom and I will have to take all the belts off PTO and drive belt. Take the crossbar above the aircleaner hose and I guess the hydraulic line for the lift deck. Might not have to take the throttle leakage and choke not sure, might be enough play on those to move. Not sure if electrical has to all come off, might be enough slack to leave them. I plan to use a V heavy duty alumminum Gorrila ladder straddle the mower over the motor and place a 4x4 across the steps adjust ladder for enough height so I can use a come along to lift it. Looks like that should would since I don't have my motor lift anymore. Its not that heavy.
The coil I will need will be for a koler CH20os, 624cc serial 2726715917, spec 64555 where can I find one for
this motor??????

2020/06/07 14:39:18

Roy

P/N 2458445S, Jacks has stock. They also list an aftermarket module, Universal p/n 055469 but it's more money.

2020/06/07 14:56:56

AVB

I don't supporting Jack's but as a business the logistics have me going to OPE on this one or my Kohler distributor.
Or you could order from OPE Engines for about $16 less for the OEM coil.

https://www.kohler-engine-parts.opeengines.com/index.php?main_page=advanced_search_result&search_in_description=1&keyword=2458445S+

2020/06/07 15:29:08

spaceman

Thanks guys for all the help.

2020/06/07 16:33:29

spaceman

I wonder if I should replace them both or leave the other one alone since its working. The mowers total hours is 552.

I hate to mess with stuff if its working and some new stuff might not be as good but I don't know. Since its a job to
get to them to replace maybe I should replace them both. What do you guys think??????????

2020/06/07 22:51:58

spaceman

Well I got the motor unbolted and pushed over to the side by taking the bolts off the bottom and the PTO and muffler off and could push the motor way over against the other side. The I was able to take the blower cover off and now I can see and service the coils. Its is real dirty in there too so Im going to blow it all clean before removing the coils.
I gave the muffler a new coat of high temp paint too. Will be ordering two new coils. So Im making my way through it and its been hot here in Florida working in my garage a little at a time taking breaks. I bought a used backup mower so I can still mow around the house while I work on the Toro:) I will upload some pictures tomorrow. I can see one thing bad about having the engine down low with blower of engine on the side, it tends to suck dust into the screen area that is fine stuff going into the flywheel area. If they had a finer screen to stop more of it. You can't get in there and clean it without taking the cover off the cowling what Im doing right now. I wish they had a way to get back into there and clean it.

2020/06/21 23:35:13

spaceman

Well my plan worked to slide the motor over to the other side by taking off the muffler and the PTO and it gave me enough room to take the Blower cover off. I cleaned the motor all up, it was real dirty. I now can see the coils and easy to get to them.
Do the coils come with instructions for the gap setting for them?
This is the one I guess I will be ordering https://www.kohler-engine-parts.opeengines.com/index.php?main_page=advanced_search_result&search_in_description=1&keyword=2458445S+ and I guess I will order two and replace them both while Im doing this.
I was just wondering about the gap settings for them?????

2020/06/29 19:09:48

Roy

.010" will be good. Lay a business card on the flywheel on the flywheel under the coil, loosen the screws and allow it to be sucked against the magnets, remove the card and you are golden.

2020/06/29 19:58:32

spaceman

Ok thanks for the info. I do have a feeler gauge too. I thought also I would take a reading on what the gap is now. The business card idea sounds good to let the whole coil sit on the magnet while you tighten the screws, sounds like a easier way then using
a narrow gauge. Thanks again.
What would we do without business cards:) they come in handy :)

2020/06/30 11:04:37

spaceman

Just for the heck of it I checked the gap on the coils as they are and the I could only get a .007 in the gap so they must have
moved a little over the years are were set real close.
So you have done more then I have ever done, this is my first setting the gaps so I will go with the business card idea and let the coil sit on it when the magnet pulls it in. That will be wider then what it has been looks like. I think these are the originals and never been changed.

2020/07/02 10:43:02

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Engine won't rev up as high on full throttle Kohler CH20OS Toro Groundmaster 120

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