My Lawnmower Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
I have now declared a quest. I have an old (ancient perhaps?) Ryobi tiller/cultivator that used to run OK. Last fall when I went to turn over my garden, no go. I figured I'd get to it as a winter project. But here we now are, almost tomato season and I dug out the tiller. No go...... So here's what I did

New spark plug
Fixed crack in fuel tank
new fuel lines ( I am sure I have them connected right)
new primer bulb
new fuel filter
carb rebuild, then a new carb
clean up of coil and flywheel 'contacts' (I think I got clearance right, about 010)
new gas mix

Pull, pull pull......the best I could get was a short run burst on starting fluid. But only one time........with spark, ought to at least pop with ether.

Checked spark from the spark plug lead , checks OK with a tester, with plug out, got spark across gap and plug grounded
removed lead from shut off switch to make sure it was not shorted

I am now pulling my hair out

Only thing I can now think of is can the magneto be weak and not fire the plug when it is installed? I will go back and check flywheel, coil gap but I am not sure how much difference that will make just to get engine to pop? I read about the flywheel magnets can get weak? But they seem pretty strong....they grab a screw driver vigorously

Anybody got any other ideas? This is now a quest...
 

·
Registered
Joined
·
2 Posts
Had very similar problem on my Ryobi 25cc (7 years old). Ran ok last year, this year no start.... pull pull pull nada zip. Ended up buying a new carb ($18 Amazon included spark plug, gasket and fuel hose and clunk filter) and did the same things as you did. Make sure the tube on the side carb that is bent down goes to the fuel pick-up, the straight tube on the bottom of carb is for the bulb and is only about an INCH into the tank. Now, 2 pushes of primer bulb and it is full. I gave up using mix your gas and use only canned TruFuel. My Ryobi runs strong like new again. Didn't have to mess with carb mix settings, perfect out of the box. Good luck keep us updated on the outcome.
 

·
Registered
Joined
·
449 Posts
Welcome to MLF Marine (Semper Fi). Do you have a compression tester? I have had machines with 60 to 70 psi run, but not well. Ideally, the closer to 100 psi the better. If compression is low or you do not have a tester, pull off the muffler and look at the piston and rings. If you see scoring or a stuck ring, you found the problem.

Is your avatar an F-4 Phantom?
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #4 ·
I got 1200 plus hours in the back seat of the world's most famous fighter.

Today, I adjusted the coil/flywheel clearance to the spec.....010-012. Had a nice solid spark on the bench with the plug out and grounded to the block. Put it all back together. nada. Not even a pop with starting fluid. I disconnected the stop switch to make sure it wasn't acting up with no difference. I had it connected on the bench and it was OK. This is now making me crazy.

I think next is to change the coil. I have 3 Ryobi weed wackers that I think have the same engine set up so I might try one of those next. But with the spark on the bench, I am at wits end.

The engine turns over nicely and while I didn't check the compression, it feels solid enough to get a pop with ether. I am wondering if its possible the flywheel might have somehow slipped but I understand its keyed and feels solid on the crank. I don't believe there is any other way to change the timing.. Its a quest

I got a compression tester somewhere so I guess that is an easy check
 

·
Founding Administrator
Joined
·
1,265 Posts
Couple things to check.

Is the cylinder nice and tight to the crankcase? They do have a tendency to come loose. 2 or 4 allen head screws hold it on.

Is the carb nice and tight to the crankcase?

Is the exhaust restriction free?

No more starting fluid! It removes the oil film off the internals and damages stuff. Get a small squirt bottle and put some mixed fuel and drip it into the carb and try starting. While you are at it, go ahead and put a drop or 2 into the spark plug hole and then put plug back in and try.

As you push the primer bulb, is fuel flowing into the carb?
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #6 ·
I figured the ether was not so good for a 2 cycle but I figured I ought to at least get a pop. But nothing . The exhaust puffs onto my leg/foot and I poked a coat hanger wire into the muffler, so its not plugged. Got a new carb, new primer bulb, new hoses, fuel flowing through the clear lines into the carb. I changed the carb after rebuilding the old carb and it did not seem to make any difference. The plug is wet so there is fuel flowing through the carb.

With the engine on a bench, I took apart the magneto/coil and set the gap to a shim I measured at .011. I believe the spec is 010 to 012 so that ought to be good. With the plug out, there is a nice spark. I even had the kill switch in the run position connected to the engine frame so it does not seem to be shorted. I got to be missing something.

Is it possible for the flywheel to move on the crank? I saw a drawing that shows its keyed and it appears/feels nice and snug where its supposed to be. So I don't know how it would move. There's nothing else to effect the timing?

Is it possible the coil is weak and won't throw a spark due to compression when the plug is installed? Seems like a reach. With the plug out it throws a nice spark.

There has to be something I am missing....grrrrrrrrrr......
 

·
Registered
Joined
·
449 Posts
Yes, it is possible for the flywheel to shear the key that is cast into it. Simple to remove and check.
Thanks for your service, Sir.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #10 ·
Rainy afternoon, so I attacked this sucker. Checked the compression (first challenge, find the tester). Only could push 35-40 at best so I took the engine apart. Bore and piston is nice but the ring is stuck. I assume its supposed to be free but its stuck/frozen in the grove with no tension/pressure onto the cylinder bore. Nothing is scored or scratched. I supposed it might have welded itself in the groove and it won't budge a bit. I stuck it in some solvent overnight with the small hope its just seriously gunked, but I am afraid it has died in place. Oddly, there is no sign of any over heat or melted metal. Any thoughts as to why a piston ring would freeze in its groove?

Next step, take a motor from my pile of not so good weed wackers to see if I can fit one of them to the tiller. I think they are the same 31cc engines with a different fuel tank
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #12 ·
Good news this morning. I soaked the ring/piston in a solvent over night which did not seem to do much. Early this AM I put it in a soak of WD40 penetrating lube and before that heated it up with a small butane torch. and I just was able to loosen half the ring.....no apparent damage so I put the loosened part back into the WD...maybe later it will all be loose. I am thinking a year or two of sitting just gunked up or froze the ring in place. There does not seem to be any damage. Not really a big deal but its nice to make progress and have some results
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #13 ·
Good and bad. I could not get the piston ring out. Snapped into a few pieces. Looks like it got corroded into the groove after sitting for a couple of years and got some moisture into the cylinder. Good lesson there. So, I got out a weed wacker with the some engine, took out its piston (checked the compression first) . Once I put that piston into the tiller engine, got compression in the 90-95 range, put it all back together, and in half an hour I was getting ready to plant my tomatoes. I'd love to find a ring, but its seems to be a bit of a mystery...I got hold of MTD who now supports the old Ryobi stuff and the person was helpful. The p/n is 791-180530, or 753-1209, I guess there were differences but the rep couldn't tell which for my machine. I found the first p/n and its like $45....for the ring! Maybe someone got a draw full some place, Its for a 35mm piston, and its about 1.6mm thick. Anyway. quest completed...
 

·
Registered
Joined
·
249 Posts
1 - 14 of 14 Posts
Top