Engine Toro Suzuki knock

I've got a 1984 Toro 21" push mower which has the 2-cycle Suzuki engine.

Lots of people have reported a knocking noise with this engine and mine is no exception. No one seems to know what causes it or how to fix it. Some people report that their engines have been knocking for years.

I haven't been using mine for a few years and decided to get it running again. While I had the engine cover off, I worked the engine brake and noticed what seemed to me to be a LOT of crankshaft endplay. Does anyone know the max/min for crankshaft endplay?

I submitted the question to Toro but got nothing from them except "contact you local dealer."

Thanks.

Toro | see if this helps, scroll down & click on service manual & see page iv-4.

Click on 26 page service manual, no crankshaft end play specs.

mechanic mark said:

Toro | see if this helps, scroll down & click on service manual & see page iv-4.

Click to expand...

Thanks, but unless I'm overlooking it, I don't see a spec for crankshaft end play.

I have no idea what the crankshaft end play for your engine is. Being a 2 cycle engine the crank shaft bearings are ball bearings. So being ball bearings you would want some end play between the bearings and the crankshaft because you don't want any side pressure on a ball bearing. The bearings themselves you wouldn't want any play in them at all. So just what do you have for end play? I wouldn't think you would want much over .005.

I would think .005 would be in the ball park. I didn't measure it when I had the cover off the engine, but it was way, WAY more than .005. More like .100".

cpurvis said:

I would think .005 would be in the ball park. I didn't measure it when I had the cover off the engine, but it was way, WAY more than .005. More like .100".

Click to expand...

Then you are looking at close to 1/8 in. of end play. It dose seem like a lot to me but maybe one of the two cycle member's will know more then me. I am just guessing from a two cycle Honda motorcycle engine I have in my shop which I think runs a lot higher RPM's. I don't even remember the last time I worked on a 2 cycle lawn mower engine.

reynoldston said:

Then you are looking at close to 1/8 in. of end play. It dose seem like a lot to me but maybe one of the two cycle member's will know more then me. I am just guessing from a two cycle Honda motorcycle engine I have in my shop which I think runs a lot higher RPM's. I don't even remember the last time I worked on a 2 cycle lawn mower engine.

Click to expand...

Yep, an enormous amount of end play. It must have needle or roller bearings as no ball bearing would tolerate that much slack.

I got hooked on 2-cycle mowers as a kid. I mowed my Grandma's yard which was about 1/2 mile away from our house. I could either push my Dad's cast-iron-everything mower to her house or rent an aluminum deck Lawn Boy from a hardware store that was a block from her house. It was well-worth the rental cost.

When I got married and my own yard to take care of, I bought a used Craftsman aluminum deck mower. Not a Lawn Boy, but still pretty light, even with its 4-cycle engine. With marriage came in-laws. With in-laws comes people wanting to borrow stuff, including the lawn mower. One of them actually checked the oil(!) and seeing that it was at the low mark on the dipstick, added a quart. Later, they called to complain that "your damned lawn mower won't run." But it had run, long enough to blow the seals out of it. It was the beginning of a very quick end for that engine. Try as I may, I couldn't keep it from fouling the points with oil, necessitating numerous flywheel removals, the last of which resulted in the tip of the crankshaft coming off with the flywheel.

That's when I bought the Toro 2-cycle. Light. No crankcase oil to worry about; no oil changes.

What I hadn't counted on was somebody (wife) trying to mow a cast iron water meter cover with it. And not telling me about it for over a year. She had a neighbor put a new blade on it and I was none the wiser.

Sometime after that, the knocking began. Bear in mind, the water meter cover incident took place at a house we moved out of 12 years ago, so this thing has been knocking for a LONG time. We only use the mower for trimming now but even at that, you'd think if it was a rod or detonation or anything serious, it would have blown up by now.

I am going to bow out on this one seeing I don't know the engine at all and don't buy into the needle or roller bearings part?

Did you remove the flywheel and check the key?
We still run these mowers. And some guys will hit something and not bend the blade but shear the key enough that it will still run but does kinda sputter or knock.
I know you said you removed engine cover so I imagine you removed the flywheel but wasn't sure But wasn't sure which end of the rod you were talking about. Just assumed top but thought maybe your talking bottom. Just wanted to rule out flywheel key.

I never noticed any significant play in either end of the rod when working on these mowers.

The flywheel has been replaced. I had to do that when the ignition coil went out and both the coil and flywheel had to be replaced as a pair. That was after the great water meter episode.

Other than the governor surging at anything other than full throttle, the engine runs great. I can live with the surging because I never run it a low power settings.

Thanks for the suggestion, though.