Also, make sure the engine is on the compression stroke before yanking on the rope. But, like Loger said if it was just serviced take it back.

sheared flywheel key?

Agree with Andy!

Thank you so much! I had our handyman trying to tell me that it just needed a shot of WD40. The repair shop told me they just worked on the carburetor, not the starting mechanism so they are not responsible. I know what you are saying is correct because of the violence of the cord retraction. It had to be mechanical. I will be back to them tomorrow.

A sheared key would throw the timing but I feel lack of proper flywheel torquing could have caused this if it was just services. Does this motor use a steel key which I would think vs my old B&S? This would lead me to not proper torque again. When I see âÂÂoldâ and if it has points vs electronic ignition, could a bad point setting be the problem and assist in damaging a key due to a kick-back?? Back to the shop is the Bottom Line, unless that is a problem. loger

Was the tiller used from the time of the recent service and this issue? If so, did you come upon any sudden resistance that basically stopped the engine instantly? Which is not common compared to a lawn mower hitting a stump etc. Aluminum keys vs steel are basically a safety feature to reduce damage or breakage as well as aligning timing. It will be interesting to hear what they find and possibly why. loger

I appreciate the continued discussion. This problem began immediately and has happened twice. The tiller hasn't been used anywhere where it could hit a snag. Interestingly, once it starts it runs ok but differently than it used to. It sort of coughs once it warms up but it keeps running. The invoice says he changed spark plug and air filter, checked operation and set carb. Check gear ease seems to be ok, put on new air filter. Used 30 w oil.Because it seems to run differently, I think the timing is off but sorry, I'm not at all mechanical. I really want to sound at least a little knowledgeable when I talk to the service people tomorrow. Thanks again.

Well, continuing frustration. Just talked to the shop owner and he tells me there is nothing wrong with the timing because it doesn't do this all of the time. His story is that it worked fine in the shop and they weren't asked to fix the starter that there was nothing wrong with!!! He says that they will replace the starter but of course there will be additional charges. I don't mind paying for work to be done but I don't have confidence in these people any more. He also said "don't go looking on the internet for problem solving".

He also said "don't go looking on the internet for problem solving".

True, alot of the time. But the advice you've been given here is professional.

Replacing the starter won't solve your problem. If you don't pull through the compression stroke, it's possible that a spark ignites the gas but the engine goes backward and rips the rope out of your hands. Slowly bring the engine, with the rope, to a point where you feel resistance and then pull harder. Out of time usually produces kick back all the time. Sounds to me like you aren't pulling hard enough.

I have an old troy bilt horse that will do the same thing. I think some of the older engines without some type of compression release and a smaller radius on the crank pulley are worse to kick. I make sure mine is on the compression stroke and pull like heck, or use the electric starter which is 110 volts and a little unhandy.

Larry

I believe that the advice I have received here IS professional and that the serviceman I spoke to is not professional. At the very least it gives me an idea about what to ask for. I absolutely hate these pull starts, they are so difficult and now I'm scared of it. I'll get my handyman to tell me about compression strokes. Thanks again. Slowpoke, what do you mean by: "use the electric starter which is 110 volts and a little unhandy?"

Some snow blowers are equipped with 110V starters, but I'm not aware of them being used elsewhere.
IF you didn't experience this problem before and do now, then something is definitely amiss.

The spark timing is controlled by the flywheel.
The flywheel has a magnet in it. When it rapidly passes by the coil (transformer basically), the magnetic field induces an electrical field that is stepped up by the coil.
When the voltage reaches a certain point, it jumps the spark plug gap producing a spark.

IF the flywheel key is sheared (sometimes they break "slightly" and then jam the flywheel preventing it from rotating further) the spark occurs at a different time than it's supposed to.
Typically they shear because the engine came to an abrupt stop and the HEAVY flywheel wants to continue to rotate. The key shears and the flywheel (with magnet) rotates a bit more. The magnet now comes by the coil that much sooner and fires prematurely in relation to the piston stroke.

Basically, the spark plug is supposed to fire just as the piston has reached the top of its stroke and is starting to head down. Spark plug fires, combustion and the expanding gases push the piston down producing power.

With the spark occurring prematurely, the piston is still coming up to the top of the stroke, spark occurs and the piston is driven back the way it was coming. OUCH!

I have the same kickback with my Troy horse (Cast iron 6HP Tecumseh) and I know it's because I'm serious enough in my pulling.

Over the years, I've had mowers with severe kickback that wouldn't start at all. The key was only moved a few thousands of an inch. I've had mowers that start up and run rough and the key is sheared and moved an inch away from its normal position. So, there is no rhyme or reason here.

I've seen a sheared key on a big Cub Lawn Tractor because the flywheel nut came loose. But in your case, it doesn't seem like the shop did anything wrong. I would specifically ask the shop if they removed the flywheel to check the points, if there are any.

baymee, Very good info. Could a recent carbon build-up cause this or add to this? I would agree that the key and points need inspecting if points are present. A Tecumseh has always been a killer because of the good power (due to better timing tolerance IMO vs a B&S that will time w/o an effort). loger

Dotty, I have an old 7 hp Tecumseh engine on my horse. Someone before me installer an electric start on it. The started motor in 110 volts rather than the standard 12 volts that most use. I don't need a battery for it, I just plug an extension cord into a receptacle on the engine and press a button, unplug the cord and I am ready to go. The started works very well but you have to have household current to operate the started. you will have to have a flywheel with teeth on it to use a 12 or 110 volt starter.

I love the fact that I don't have to fool with a battery. I just keep a 100' extension cord plugged in and drag it over to the tiller if I don't want to crank it. It only takes 1 or 2 pulls to start the tiller, but if it kicks it feels like it is ripping fingers off.

Larry

As always, excellent information here. dotty mentions "old" without telling us how old. Most of you would consider me "old" but I'm still firing on all cylinders....:-)

Couple of things bother me, if the tiller is "old" then the owners would be used to it's starting idocyncracies (sp?) and the sudden kickback seems new. The group opinion is that this is a timing issue, and I agree. If the "service" outfit doesn't recognize that, it's time to find another outfit. Also, replacing a flywheel key isn't major surgery for a "service" outfit. There's also the fact that in changing a plug, air filter, and setting the carb, it is highly unlikely that the timing was changed or degraded.

So, it would seem there's still more to the story, or the flywheel key was previously partially sheared and decided to move "just enough" to cause this timing issue coincidentally to the yearly service. I know I've had engines that were running fine and "suddenly" started acting up without hitting any major bumps or obstacles and it was the flywheel key. Cheap fix.

Good luck,

Ev

Carbon buildup would increase compression and make the engine more difficult to pullstart. We could also be looking at a coincidental occurrence of kickback. Key question is if they pulled the flywheel for any reason.

IMO I think the big question here? Do the machine have points? Did the recent routine service provided required the points to be replaced or checked? IF so they had to remove the flywheel to get to the points to either inspect them or replace them. Now the flywheel key could be factory or the engine tune-up was degraded from lack of preventive maintenance that it wouldn't kick back.

IMO I would first think the owner didn't pull it up to the compression stroke before attempting to start as stated. Usually older tiller engines don't have the compression to kick back due to lack of maintenance (oil changes, points plugs and decarborizing) I dought it in the key unless they tampered with the points and left it loose. I dought they went that far into the ROUTINE servicing. IMO That's how they probably know it wasn't them casuing the problem cause it starts fine for them when they pull it up to the compression stroke and are strong enough to pull it pass the next compression stroke..

""That's how they probably know it wasn't them casuing the problem cause it starts fine for them when they pull it up to the compression stroke and are strong enough to pull it pass the next compression stroke..""

My opinion too. As a strong man, I can start almost any mower with one pull. For an older woman, it can be a whole different story. So, knowing that, I usually don't let mowers out of the shop unless they can be started reasonably easy.

Sometimes this means a little more work on the carb, primer, or whatever. Since I have about 800 customers on my list, I can pretty quickly weed out a sheared key issue from another kickback cause.

i have had a similar issue with my craftsman my issue was self inflicted I overfilled the oil during change I had filled it to the upper cap it. suddenly it had massive kickback after several pulls it started and oil and smoke was pouring out muffler. I drained the oil, refilled to proper level, changed spark plug, it still has some kickback but not nearly as bad and backfires when shut off.my next step is to check flywheel to see if key has been sheared

Thanks. This was several years ago and the repairman had screwed up the timing. Took it back to another repair shop and they fixed it. I am STILL nervous starting it though, it almost broke my hand. Sort of like the original motor cars.

Dotty,

1. Can you summarize what the
2nd repair shop found as the problem or problems and Fixes?

2. I have an MTD 21” mower I
   have used just at the start of the season to collect leaves. I have dreaded the 2-3 pulls to start the
   mower with fresh Stabil treated fuel (after leaving some in the mower treated
   for a year, thinking varnish vs moisture).
   I should have been leaving a full
   tank to not draw moisture or Bone Dry.
   Once start, it feels easy like it has compression release. I plan to start rotating my 2 mower vs
   letting the MTD sit and the Murray
   has always been first pull.

3. Since the mid 60s I have had
   some “Kickbacks and they all were Tecumseh engines from my memory vs Briggs. I
   got bold and started my MTD with a ½ drill (with a side handle in case it
   kicked back. It had never kicked back
   and it started. I am not promoting the
   drill but I am suggesting electric start if there is a kit for your tiller.

4. I put my recoil starter back
   on using 1/4 X 20 bolts clips to thread the bolts into. I did this a week ago and it started 1st
   pull today. I pulled too harder. LOL!

Okay Guys got a troy built tiller with same issues. It has so much kick back that it has broke the recoil before and now it will cause such a whip lash it will bruise your hand. I have looked at the key in the flywheel and it looks like it has not moved. I have replaced the carb since old one was to trashy to keep clean. It has the old cast iron heavy flywheel and I am afraid to pull the rope. I have used the compression stroke to try to control but no success.

I see my original post was 4 years ago. The tiller has started ok since then, never on the first pull, but never with the kick back. I'm still afraid of it though and make my handyman start it first thing in the springtime. Good luck with your issues, there are some wonderful responses in this thread.

Will gas getting into the oil cause kickback.?

Gas in the oil could hydraulic / lock an engine in Severe carburetor leak by into the crankcase. However a very remote possibility . Much more prevalent within diesel application , where a high pressure lift pump can quickly fill the cylinders with fuel from defective (leaking injectors ) A more serious scenario is smaller amount of gas contaminating the oil and causing a engine seizure issue after continued usage .

Hello All, Be Careful! I will still stand behind a timing issue in the 70s I feel electronics should have helped or eliminated points. The flywheel was the next issue if the key’s
fit was damaged from the blade striking an object or not torque good. Good luck
on the new technology.

Hey Loger , don,t be such a stranger ..eh !

I am having a hard time getting in to share. I have my firewood experiences to share. I’m trying to stay with two electric chainsaws 14” Mac and 16”Wen. After my 3, 70’s 16” Poland S-25 saws have worn my starter arm out (they still work fine with no primers). I am considering a Poland “Wild Thing” to use my surplus of 16” bars and chains.

I have been spoiled from salvaging wood left on the curbs for our Bulk Pick-Up by the City (in our old neighborhood). I have not used my gas saws in 4-5 years and my 10-12 ton Log Splitter is Electric. I have become a Wimp from not using my 70s Gas Saws. My body is enjoying the scaled back work with the 1.5 cord ready to burn and 1.5 seasoning.

Hey nothing wrong with electrics today Bud ! We have had quite a few new threads on electric lawn tractors merit along with electric push mowers . Glad to hear your fire wood sourcing is going well , same here cut and split this yrs and almost done storing it away . Take care and keep sharing !

my tiller would break your arm tried everything. i found the valves on a ohv needed to be adjusted . just done that and ( no ) more kickback . it was easy.