Ryobi 4 cycle motor

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  #1  
Old 03-19-12, 10:51 AM
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Ryobi 4 cycle motor

Have had this product about 14 months and has worked very well. Used it the other day and finished my work put it away and went back about a 4 days later and it would not start. Checked gas, removed the cover and checked sparkplug it had spark. Just out of curiosity plugged up the spark plug how and checked for compression and it has no compression. I removed the valve cover and the valves seem to have the same amount of space.
What else is there to check without sending it to someone that will charge and arm and a leg to check it out?

Thanks
 
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  #2  
Old 03-19-12, 06:59 PM
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Not sure what you mean about the valves having the same space. Are you talking about the amount of space between the rocker arm and valve stem? Do both valves move up and down?
 
  #3  
Old 03-20-12, 05:11 AM
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You did not say what motor you have or even what type of machine it is on so it's hard to offer any specific help. It is possible that the motor has a compression release which would mean you feel very little or no compression when turning the motor over slowly.

If it's totally dead, not even trying to fire, then I look at ignition but since you say you are getting spark that should not be the case. Just to be safe I would insure that there are no broken wires or shorts in the cut off circuit.

Does the engine have a low oil shutoff? If so, insure that there is sufficient oil in the engine. If that does not help check to see if the sensor/switch mounted to the side of the engine case is working properly.

Did anything happen to the engine or did it make any funny sounds when you used it last?
 
  #4  
Old 03-20-12, 07:07 AM
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Ryobi 4 cycle motor

First off thanks for the response.
The unit is a Ryobi Expand-It 4 Cycle 30cc Trimmer Power Head RY34000. By the valves having the same distance, I meant that they had the same amount of clearance from the rocker are and the valve, and yes the valves move up and down and I could push them all the way donw and they would move back to the same positon they were in. Something I thought about yesterday while talking to someone was that the belt that drives the OHC might have jumped, even though it was running when i shut it down and it just didnít start the next time. It did sometimes have a sputter as thought something very small might have kept one of the valves open just briefly. The unit is fairly new so I wouldn't think the belt was loose enough to jump, but I guess anything is possible. I have to check if the valves are closed when the piston is TDC and on the compression stroke.. I checked the switch, before I took the cover off to check the spark plug. Since the OHC is the only thing that is driven by the belt, the spark would be fine even though the valves would be closed. I checked the compression by putting my finer in the spark plug hole and pulling the rope should have had some compression. Oil is ok, if it had a low oil sensor I would think it would kill the spark. Thanks.
 

Last edited by larrybeierle; 03-20-12 at 07:09 AM. Reason: Added info
  #5  
Old 03-20-12, 08:00 AM
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Put a pencil or something in the spark plug hold and pull the engine slowly and see if the piston is moving.
 
  #6  
Old 03-20-12, 08:08 AM
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Ryobi 4 cycle motor

Thanks, I will try this tonight. that way i can check if the valves are closed when the piston is TDC. Have a great day.
 
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