90 312-H Carburetor adjustment

[Detector 72]

On this new to me 312-H I'm still working out the bugs...My Kohler manual is vague on the high speed air/fuel setting, my carburetor looks like this type  http://outdoorpowerinfo.com/repairs/kohler_walbro_whg_adjustable_carb.asp. My manual has the procedure for the Adj. Jet carb with the main fuel needle at the top but not for the fixed jet version I'm assuming I have. The adjustments I'm curious about photo is #13 in blue/pink, what is the adjustment procedure? Cannot seem to find anything on it. The link does not go into actual tuning. Also info on idle RPM and high speed RPM. It starts & idles fine and revs to full throttle fine and doesn't skip a beat, doesn't use any oil but acts as if it is under a very slight load at wot in neutral/PTO disengaged, kinda like a generator running free vs having a load on it...Does the hydro unit suck a lot of HP from the M12? I read somewhere that it does compared to the 312-8 gear drive versions but I'm not sure how much difference. It has new fuel lines,, fuel pump, new fuel & air filter, fuel shut off valve w/screen, new air filter as well as the spark plug. It mows good but just seems to be lacking some power, perhaps I got accustomed to my other mower with the 15.5 Kohler Command/gear drive. I have not made any carb adjustments at all & it may need none but just in case I'll know how. The previous owner took it to a shop to replace the fuel pump last month prior to selling it, I pulled the bowl just to check for any trash and it was spotless so I assume they cleaned it.  You guys have been a great help so far on helping me with my new project and it's very much appreciated, learned a lot in the short time I've owned it

Edited August 10, 2016 by Detector
add info...

[Hossenfeffa 49]

Screw at the top is your idle mixture. Have engine at operating temperature. Make sure your idle speed is close to spec. Turn the idle mixture screw in until the engine rpm changes.  Then turn the screw back out I till the engine starts to run poorly( rpm change again)  Set the screw to the middle of these two settings. Basically you want the smoothest running at idle. The high speed mixture screw is the lower one. Make sure your high idle rpm is close( probably 3600)  Basically the the same procedure. Adjust the screw for the smoothest running and highest rpm

Edited August 10, 2016 by Hossenfeffa

[Detector 72]

Had a chance to check the carburetor settings... Without any load on the engine the sweet spot between the two points gives me 3300 rpm, whoever adjusted it had it very close, the only way I see to get it at 3600 is to put the governor spring in another notch but think I'll leave it where it is. Kinda hard to listen with the deck going to adjust high idle....Low idle I have not touched which is around 1600 "a tad high" bugs getting bad so I'll adjust the idle later. Runs well overall

Edited August 18, 2016 by Detector

[Detector 72]

After some more adjustments I get from 3240-3300 without a load & 3000 mowing which my be normal with wear over the years. I'm wondering if the governor spring got put in another notch at some point, cannot find any links to verify what notch the spring is suppose to be in for the 90 model 312-H 

[gwest_ca-(File Mod) 10,475]

The spring location only changes the governor sensitivity.

The maximum rpm is adjusted by limiting the travel of the throttle cable.

 

Garry

[Detector 72]

Thanks Garry, the old WH is new to me as well as the older Kohlers, I'm slowly learning. I'll check to insure the cable is opening all the way at WOT but if I can recall correctly the cable is adjusted as far down as it will go. I'll look again at it this evening.

Where the choke/throttle bracket mounts on the engine flywheel cover I remember seeing a slot ( with a bolt securing it, is this bracket adjustable? 

[Hossenfeffa 49]

Look where your throttle cable hooks to the lever where one end of the governor also hooks. There should be a stop which is bent at a 90 degree angle. Just loosen the bolt with a 7/16 wrench and move the stop clockwise for more rpm

[Detector 72]

Thanks found it, added a pic for reference 

Edited August 22, 2016 by Detector

[Hossenfeffa 49]

Looks different than whats on my 312-8, but that should be it!

[Detector 72]

Yep, looks different. Here is a pic facing the fuel pump under the air cleaner, some year variations I suppose

[slammer302 2,154]

I remember reading somewhere that sum of the kohler magnums carbs were set to run at 3400rpm instead of the normal 3600rpm. 

[Detector 72]

On 8/22/2016 at 9:36 PM, slammer302 said:

I remember reading somewhere that sum of the kohler magnums carbs were set to run at 3400rpm instead of the normal 3600rpm. 

Slammer, you are correct on that...In my 1990 owners manual it states 3400 RPM without load. Thanks

[Detector 72]

Well my WH project has slowed a bit but still tinkering... I pulled the bowl last year and checked the carb for trash and the needle condition, the PO said he had it rebuilt but didn't say when., all looked good. I did some adjusting last year posted above but it seems to be running on the rich side looking at the plug as well as the exhaust smell. My Walbro carb looks like photo #1 in this link http://outdoorpowerinfo.com/repairs/kohler_walbro_whg_adjustable_carb.asp This would be considered as Walbro Adjustable Jet series correct? If so the preliminary settings would be Low idle 1-3/4 turns out and the main at 1-1/8 turns out. The manual the PO give to me only shows the Kohler carburetor and not the Walbro