[twmattox]

So, now that I have rebuilt the Walbro LMR-16 carb, cleaned the exhaust ports, and added the new coil, I am trying to dial it all in. Pretty sure I have the altitude screw adjusted correctly (started at 5/8-3/4 turn pen then tightened in until started to run poorly then backed out until it ran best). But, how do I set the RPM? Well, I understand I turn the adjustable collar on the carb...but, how do I know when I reach 3200rpm?

I have preset the air vane governor (per the manual hold the carburetor with the mounting flange facing you and the throttle wide open preset the governor by turning the collar so that the winnow on the collar is 3-4 clicks to the right of the pulse hole). I get it to run quite well and can mow the lawn with it...but, I worry that I am either too high an RPM or too low. Especially when I noticed that the throttle lever really doesn't do anything at all regarding speed. I have triple checked that the governor spring is correctly connected to the throttle linkage. But, I can put it on "tortoise" and it runs just as fast as it does on "hare". I can see the linkage move and the spring move...just doesn't affect speed at all. Makes me think I am not dialed in to the correct RPM.

So, for those who do this as a hobby and don't have all the fancy equipment...

HOW DO YOU KNOW YOUR RPM???

 

[Yard Nazi]

Hi! I am sure there are many here on the forum that will say they can tune their mowers by ear and maybe they can get it close that way. I have been using Lawnboys for over 40 years, everything from the old C series, D-400 Bricktops, D-600 series, and F series and even when they are running at the proper RPM they all sound different. The only true way is to purchase an RPM tester or if you are in good with your local repair shop you could take your mower there and ask them to check the RPM for you. There are small digital testers available on eBay that are cheap and the Vibratach which uses a vibrating wire and the vibration of the mower to check RPM (these work real well) are a couple of choices. There are more expensive laser photo testers as well so your choices are only limited to your budget and your amount of use. Just curious what model F mower you are testing? Bill

 

[twmattox]

It is a 1991 L21ZPNC. I kind of prefer the primer start over the choke; but, the F is certainly a much better sounding mower over my trashed out V. The exhaust sound is less "tinney".

 

[twmattox]

I did a quick ebay search and may just not know what I am looking for. What I found was over $150... Mind pointing me in the right direction?

 

[WhyZed]

These are not Swiss Watches. It is not 'critical' to be at an exact rpm. Earth will not spin backwards if your F turns at 3100 or 3300 RPM.

Your F should have a LIGHT and NORMAL switch. If your mower bogs down on the NORMAL setting, then tweak up the RPM up so that the engine can handle the load. Remember, the stated/rated RPM is under load RPM and the governor is there to hold that RPM. ((If you have neglected your growth to require a higher RPM then the normal setting, then go ahead and make the adjustment (or stop & sharpen the blade) - then lower it after the task is complete)). Then acquire a lawn tractor and sell me your push mower cuz you are abusing your LawnBoy. $20.00 Bucks!! :1221: Bustin my balls!!! lol

If your mower is racing (even on the LIGHT setting) while cutting your lawn then make the simple adjustment to lower the RPM to accommodate the task.

Keep your blade SHARP SHARP SHARP!!!! And lower your RPM..

Save the planet and kill the Archons!!!!!!
Research Archons and return to Human!!!

 

[Jackass]

Search for "Small Engine Tachometer" on ebay and you will see lots of much more affordable options.

This is roughly what I purchased to use.

 

[Yard Nazi]

Hi! Here also is a link to the Vibra Tach I spoke of although I did not pay anywhere near this amount for mine. They do work very well and are simple to use. I have tested mine against my digital one just as a comparison and it was right on. On a side note it is probably better to err on the low side when setting your RPM without equipment. I doubt anyone ever blew up an engine running it a bit on the slow side. Bill

 

[Hammerdown]

Hello
As Lawn-Boy says all Govenor settings are checked & set at the factory before they leave there. With that in mind springs weaken over time. in making the Govenor adjustment's they say that each click on the thumb wheel work's out to a 50 RPM engine increase. I would Just keep that in mind when adjusting the Govenor to be safe. Most 2-cycle engines have a shorter Power curve than 4-cycle engine'ws and over adjusting it to go over the Maximum power range curve it was designed for & that is just Taxing the Internal part's of the engines and let's face it, These engines are Not New any more. Adjust as you feel you need to , but Keep in mind the time span of these engines Plus the wear on them now & The Only way to squeeze more Horsepower out of a two-cycle engine is to Raise the Port's in the cylinder Jug and increase the fuel Nozzle and who want's to get into all that, do you really need that to mow your Yard ? it aint rocket science here, OMC designed these to run efficent & last at the factory setting's therefore I would suggest Minimal clicking of that Govenor adjustment turn wheel or it could and May Blow up in your face...:hide: I am Not a Huge Fan of the Higher Horsepower engines that Lawn-Boy made Primarily The Dura-Force. They always' seem to be much more trouble than they are worth as I have not heard of one not needing it's carburetor Played with to attempt to diminish the Dura-Surge. When it is all sorted out, These engines will Eat Much more fuel and to me that is meaningless when a Standard F-series engine with 4.5 Horsepower can and will do a Good Job and cost's Much less to run as well as run's much Better than The Dura-Surge engines do.. Just my Two Cent's here...Regards, Hammerdown