I spoke with a long time Lawn-Boy mechanic about the M series. He said he knew of no oil injection problems. It's a myth in my opinion. I like the "M" series. Lawn-Boy's best mulching deck ever. It's magnesium too. Great bagger and side discharge with the chute. I believe it to be one of the best Lawn-Boy designs. It has a steel one piece connecting rod with a pressed crank for super durability. The engine is also piston port like the "much admired" Suzuki on Toro mowers. I still have my injection hooked up. I have two of the M series mowers. I use Amsoil synthetic 2 cycle oil at 50:1 ratios. I also usually use premix in it as well because I use premix in almost everything. It's also a little extra insurance just in case.When using a synthetic oil you will notice very little to no smoke. Always turn the fuel off at the tank or you may notice some smoke from accumulation of leaked down gas in the engine upon start-up. Most of my Lawn-Boys smoke at first a little on any oil but are completely smokeless at operating temperature. The Lawn-Boy M series is designed to run at 64:1 ratio. By the way there is a shut off switch in the oil tank to prevent running out of oil. Mine shuts the mower off early. Still some oil in then tank . So if you notice your mower shutting off for no apparent reason fill the oil tank back up. Mine will shut down with a half inch of oil still in the tank. Apparently they made it this way to prevent sucking air on slopes with low oil levels. You wouldn't want any interuption in the oil flow at 64:1.

Hey echoman. I almost forgot. I have an Echo Lawnmower. It's a 2-cycle self propelled 140cc Echo mower. I love it. Do you have one of these?

I actually just the other day, through some reading, found out that Echo had made a push mower. Can you post some pictures of it? Would love to see one in person. Can you still get parts for it through Echo? It seems they start cutting down on factory production parts when equipment reaches close to 25 years old. I actually, through Echo's recommendation, found a guy in Bowling Green Kentucky, called ChainSaw World who actually had a complete drive shaft and gearhead combo new in the box for my old Echo trimmer! This was a serious score! Very hard to find if ever again N.O.S. You guys with older or rare equipment need to check this guy out! He's got STUFF! This guy has parts from equipment produced all over the world! He says he ships to all over the world as well! Getting back to the M-series, you say you run a 50:1 premix ontop of the factory injection of 64:1? What brand oil do you use and do you get any excessive fouling or carbon build up?

Thanks for the tip on Echo parts. I use the Echo mower once or twice a year just to keep it running. I think engine parts might be tough to get if I needed any but the engine is new so I'm not concerned.
On my practice of running both injection and premix in my "M" series....It's more just my laziness. I should either unhook the injector or use straight gas. I haven't had any plug problems and very little smoke. I run Amsoil synthetic 2 cycle oil most of the time and sometimes I use Opti-2 at 50:1.

I own an M-series (M21BMRC) that was purchased new in 1992.

Regarding your question...
"Who out there, have disconnected, for peace of mind insurance, and who still runs the injection system as made from the factory?"

I have run my mower only with the injection system. In the 14 years I have had it, I have never put any premix in the tank.

As was mentioned earlier in the thread, the factory specified ratio is 64:1.

Something else that you might enjoy... if you don't have the Lawnboy M-series repair manual, it was available as a free download from www.lawnboy.com the last time I checked.

Thanks for your comment adkinsca. Have you or any one that owns an M series, had the notorious cracking in the fuel tank around the shut off valve? Mine was cracked when I bought it, but I managed to seal it up using a plastic patching epoxy. It's held so far. I did manage to find a new old stock tank that was for premixing only, so if this tank fails again, unless I find another injection combo tank, I'll have to disconnect and run premix. The mower is exceptionally clean so I'd really like to keep the injection set up. I thought I read somewhere awhile back where someone(business) was selling these tanks still for around $50?. I did manage also to find a manual on E-bay.

echoman,

I haven't had any problems with my personal mower. I have seen other posters on forums mention problems with cracked fuel tanks.

There was a recall on the fuel tank around 1994. The recall was for potential leaks if I remember correctly. The visual difference that I noticed when mine was changed out was that the replacement tank assembly had a metal fuel shut-off valve as opposed to a plastic one on the original tank. There were also fewer mounting screws holding the tank within the assembly. I believe the updated tank has only a single screw in the middle where the original had three screws visible from the top.

It is possible that several of the mowers which are having tank problems never had the recall performed.

I haven't looked closely at the premix vs. injection tank assemblies, but can you swap the plastic fuel tanks between the two assemblies?

Out of curiosity, what is the model number of your M-series?

There is actually an oil resevoir built in next to the tank for premix with the hole in the bottom for the oil sending unit, but no cap built in to the top to add oil. It might be able to be customized, but had no intention to do so or really see if it would be possible. My model number is M21EMR. Has all the options but the brake blade clutch.

have for sale a Lawn Boy M21EMR.. like to sell just the motor..not too crazy about this oil injected engine...I bought the whole mower off of ebay...I live in Baltimore Md.

I know this is sick but I LOVED my Lawn Boy M21EMR series mower. However it has cracked the fuel tank again (93-1208 - replaces 684140) and I can't find another one anywhere.

I have tried patching it and it doesn't hold. Considering adding a fuel tank on it somewhere - I know, I need to TOSS it.

If anyone has any suggestions I would appreciate it.

thanks

One on Ebay. Says that the oil hose connector is broken but can be repaired. $30.00.

Appears to me that it would be a simple fix with a brass threaded to hose barb elbow.

{{gwi:322248}}C&P the URL to view the tank.

http://www.ebay.com/itm/LAWN-BOY-Gas-Fuel-Tank-/151302200221?pt=LH_DefaultDomain_0amp;hash=item233a505b9d

DON'T YOU HAVE SEAL OFF THE OIL LINE IF YOU USE A PRE MIX TANK

I just completed a M-Series and guess what The tank is leaking grass Tank is cracked Anyone out there retro a different tank on these Units ????

I have a M-Series and had to replace the cracked gas tank by another one that don't have the oil cap. I can live with the fact that I'll have to mix gas. So I have blocked the oil line but it seems that there is a sensor or something else that cut off the motor because it is running out of oil !

Is there a way to bypass this security ?

Thanks,

Jean

Any of the safety switches can simply be disconnected. They ground out a part of the ignition circuit to kill the engine and are open circuit for normal operation. Over the years, the safety switches for the oil level and for making sure the bag or discharge chute is attached have failed on my M-series mower. The cost of these little magnetic reed switches is ridiculous, if you can even find them. So I've simply located their terminations and unplugged them. I can see when the oil is low, and I'm smart enough not to reach my hand into the discharge area while the blade is spinning. Lawn mowers never had all of these safety devices when I was a kid. They're a byproduct of our litigious society. However bypass safety features at your own risk. I certainly won't assume responsibility. Of course, in your case, the oil will be mixed with the fuel, so there is no safety concern.