Ryobi 990r 4 cycle clutch removal

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  #1  
Old 03-16-05, 08:07 PM
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Ryobi 990r 4 cycle clutch removal

Hello all! I have a Ryobi 990r on the bench that will not crank and after looking it over carefully I suspect it has an almost shered key. I've torn it down to the clutch. I'm a little afraid to bull forward without knowing whats around the bend. I don't have a book and this is my first encounter with a 990r. What is the best apporach to secure the shaft, remove the clutch and reach the flywheel? Thanks in advance, Ron!
 
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  #2  
Old 03-17-05, 01:17 AM
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Hi Ron!!

Unfortunately, I am not familiar with ryobi products by model# and I don't have any manuals on them. Actually, maybe that's not so unfortunate, lol, but anyway...

Most times, there is a screw down in the center of the clutch bell. It may be reverse threads (left). You can remove the spark plug, insert some rope into the plug hole, and this will keep the crankshaft from turning. Once the bell is removed, the clutch plates will have to come off. They are probably 2 stamped pieces of flat metal in somewhat of an "S" shape. You can use a punch and hammer to knock them in the direction required for removal. Once removed, you should have access to the flywheel. You may have to unbolt the engine from the plastic housing.

Hopefully this info is accurate for the trimmer you are working on. If not, let us know!

Just a thought: Although it is not unheard of, flywheel keys don't often shear on trimmers. Sometimes they do work loose and wallow out the keyway. I've seen a few sheared though, so you may be right on target.
 
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Old 03-17-05, 01:53 AM
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Cheese, you said "You are probably right on target". This should be carefully reconsidered as I always check the picture tube first and find the problem is that the unit was not pluged in in the first place! I have a carb kit that will solve the problem but the unit is owned by a fellow who absolutely will not let me buy the parts. He went and picked up the kit so I am checking the key in hopes thats the problem and I can save the fellow $18.00. This is by far the smallest 4 cycle engine I've ever worked on. Looks just like a 2 cylinder except for the oil sump and the OHV's...Duh! The rope thing is exactly what I needed. See, you're never too old to learn. This will help on a lot of things in the future! I will let you know. "Thank you again", Ron
 
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Old 03-17-05, 03:13 AM
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The key on these engines is integral to the flywheel, so if in fact the key is sheared, you will have to buy a new flywheel. The screw in the clutch "bell" housing should not be left-hand and typically is a torx head screw requiring a T-20 driver for removal. I would like to mention that although possible, it is rare that the key shears. By all means check it out though using the rope-in-the-cylinder trick cheese mentioned.
 
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Old 03-17-05, 05:49 PM
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Thanks much for this invaluable info!!! I'm going to get started about 11:00 AM so I'll have more questions tomorrow night or a great report. I still can't get over the rope trick...I'd never in this lifetime have thought of that one. Can you tell I'm new to all of this. Thx again, Ron
 
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Old 03-18-05, 09:11 PM
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The latest report

O.K. here is where I am. I could have moved ahead but in an abundance of caution I thought I'd get your thoughts! The rope is perfect and I have the shaft completely stable. The Clutch, as it turns out, has no center screw. I have removed the pads and I'm left with the 'S' shape center section of the clutch. Stamped on it is the word off and an arrow pointing to the left. I was going to lay a block of wood under the lip of the 'S' and strick the block with my hammer forcing it in the direction of the arrow. I have put penetrating oil on it and am letting it sit over night. Should I go forward or am I missing something??.....Now, I know your right about this key. With a weedeater the shaft is going to absorb all the shock. It is improbable that that energy would be so great as to sheer the key?&*^%$*& I am at least learning how to get to the flywheel if I need to in the future. I appreciate your help, Ron
 
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Old 03-18-05, 11:38 PM
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Full steam ahead. You're doing it right. What was the fastening device that held the clutch bell on?
 
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Old 03-19-05, 04:25 AM
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I assume the clutch bell is the "Entire Device" that the clutch pads came off of? If so, it appears to just screw on and off. Now screws. The bell itself is tapped and just screws onto the shaft? I'm just crawling out this A.M.. Will report in tonight. Thanks again, Ron P.S. Cheese, I still can't get over that rope trick. It works perfectly and has made me look really good amoung friends who have no idea how to stabalize the shaft!!
 

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  #9  
Old 03-19-05, 05:12 AM
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O.K. after taking a close look I think ya'll are talking about the clutch cover. The drive shaft is attached to it. It is what the Clutch pads grip at speed. If that is the 'Bell Housing' and it looks like a bell...Duh...then it was attached with 3 T-20 Torex screws equallatteral around the bell housing! My first few taps at getting the 'S' off were unsuccessful. I'm waiting on some muscle to show up. My son is coming over today. Cheese he wants us to build an ultra-light so he can fly to work. How many have you built and can you or anyone else direct me to a really good forum on the subject? As always Thank You, Ron
 
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Old 03-20-05, 12:37 AM
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I've never built one Ron. I have thought about it many times, and I might do it one day, but I just don't have the time for projects lately. My last project like that was started over 2 years ago, and still isn't finished. I don't know where to find info about them, but I'm sure a search on Google would turn up lots of stuff. You might consider what kind of permits and regulations apply to ultralights too.
 
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Old 03-20-05, 08:21 PM
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Struck Pay Dirt ! Well with your help I have succcccessssssfullllly reached the Flywheel! I found a new way to strike difficult clutches. I cut a piece of 1/2 inch Sch. 40 PVC and used it in place of my trusty block of wood or chisel. This worked well. After passing the clutch I had my son pry the flywheel with 2 screw drivers with min. pressure. I put a piece of wood on the shaft and struck it pretty hard 3 times and it released. To my great suprise there is a key on these 990r's. It is independent and not built into the flywheel. As you can imagine to my great pleasure it was severely nicked on top ...and is likely the problem. The nick is on the rounded top of the key so it had to be a bad key when installed! The nick had forced the key down the shaft during manufacture of the unit? Now, finding a replacement may be a challenge. This key is VERY small. I had to use locking twisers from the hospital to handle it? I'll let you know tomorrow if the key was really the problem (If I can find a replacement?). This is my last resort before rebuilding the carb.This has been a real learning experience. Cheese, if you get a 990r into the shop ...call me. I'm now an expert...HA! My son said, "Cheese can fly our ultra-light anytime..does he realize that you (me,Ron) are handling the engine issues"? Thank you all very much, Ron
 
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Old 03-21-05, 12:27 AM
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Well, I'm glad you got the flywheel off! Was the key actually sheared at all, or distorted in a manner that would affect the magnet position in relation to the crankshaft? Hopefully that is your problem.

Tell your son I said "thanks for the invitation, and who knows? Maybe I'll get the nerve to try it one day." If I see an ultralight flying over my area, I'll be waving. There aren't many around here, so I'll assume it's you, lol. (look for the waving guy with a blonde flat-top haircut and a big grin).

What kind of engine have you got in mind for the ultralight? There are regulations that apply to aircraft engines. I don't know if they apply to ultralights or not, but if I had to choose one, I think I'd go with a honda GX series if it was acceptable for use.
 
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Old 03-21-05, 02:45 AM
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Cheese, this key is NOT made of soft metal but is VERY thin. It sure would have been less expensive for Ryobi to have a flywheel with a built in key as Puey suggested earlier? I've seen Briggs keys that actually look like an 'S' because the part in the flywheel is offset from that in the shaft by fractions. This is not the case here! The top of the key the part in the flywheel was nicked and was 'pushed' down from it's normal position. It was down from where I think it should have been...obviously I have nothing this size to compare it to so I can't be sure. I have great hope that it will crank but I haven't returned the carb kit yet. "Stay Tuned", A report later!!! As for ultra-light engines I'm just starting to look around??? Google 'ROTEX' and take a look at these South Africa manufactured engines. We are looking at the smallest 2 cycle. I think it is 36hp. This is just the first "Aircraft Engine" site I have looked at. They have blades, data systems as well as communications gear. It is my understanding that there is NO liscense requirements if it is single seat and doesn't fly over 500'. Thanks for the nudge we will be sure early on as to the regs. We discussed proto-type vs. kit. You know how these 25 year old children are but I think I have convinced that we really should go with a proven design! I'm getting pretty interested so I guess we'll put a little cash and brow sweat in and see what comes out the other end of the tunnel? I really thank ya'll for keeping the forum as oneof the best if not the best on the I. My appreciation to you all, Ron (PS Got to run...no spelling review...good luck)
 
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