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Hi guys, I just joined the group hoping someone might point me in the right direction with my problem.

I have a Ryobi blower/vac with the 25.4cc "full crank" engine which up until yesterday, has always started easily and run fine. My wife first told me that she couldn't get it it to start and that she thought the pull start was slipping as there was little resistance when she pulled the cord. It felt to me like there was normal compression if I pulled the cord slowly but if I yanked it, it seemed to almost freewheel. I pulled it apart and the start system looks fine. I pulled the plug and it was wet with fuel. I grounded the plug and pulled the engine over and there is spark. I removed the carb and exhaust to look at the piston and the rings are there and literally nothing on the piston, no scores or scratches and it moves up and down. I put it all back together and same result although now the compression seems to be normal when pulling the engine over. My imagination? Possibly... It will not even fire with a gut full of Aerostart.

Is there a keyway that the flywheel locates on that might be sheared? Is it possible the shaft can half slip half grab with a sheared key?

Any help will be greatly appreciated. Thanks
 

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You're describing more than one problem, although the initial problem could be explained by a sheared flywheel key if the starter engages said flywheel. Not turning crankshaft over when pulling rope due to flywheel not engaging crank gives symptom of no compression because the crank isn't turning.

The plug getting wet yet won't start without spray prime usually indicates there's either scoring of the piston or cylinder (scavenge issue), or a crankcase vacuum leak (such as cylinder/intake/CC gasket or crank seal). You state there's no scoring...so I'd look for leak. Re-using gaskets isn't advised, if you must re-use at least put some ultra-black/ultra-copper or similar high quality, fuel-impervious sealer on them or mating surfaces. Cheap, blue or red RTV won't cut it.
 

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Discussion Starter #3
You're describing more than one problem, although the initial problem could be explained by a sheared flywheel key if the starter engages said flywheel. Not turning crankshaft over when pulling rope due to flywheel not engaging crank gives symptom of no compression because the crank isn't turning.

The plug getting wet yet won't start without spray prime usually indicates there's either scoring of the piston or cylinder (scavenge issue), or a crankcase vacuum leak (such as cylinder/intake/CC gasket or crank seal). You state there's no scoring...so I'd look for leak. Re-using gaskets isn't advised, if you must re-use at least put some ultra-black/ultra-copper or similar high quality, fuel-impervious sealer on them or mating surfaces. Cheap, blue or red RTV won't cut it.
Thanks Paul, you've given me somewhere to look
 

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Thanks Paul, you've given me somewhere to look
I’ve had a better look and there is scoring on the piston. I missed it before as it’s close to one edge of the exhaust port. I assume it’s uneconomical to try and rebuild these engines?
 

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Rebuilding a box-store almost anything is usually not cost-effective. But then again, I've had people on this site tell me they'll do it for the experience/education, and as a former instructor I commend such self-improvement efforts of any type, if within fiscal reach. But you sound like you have a decent grasp on repairs, so it probably will come down to a fiscal decision.
 

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Rebuilding a box-store almost anything is usually not cost-effective. But then again, I've had people on this site tell me they'll do it for the experience/education, and as a former instructor I commend such self-improvement efforts of any type, if within fiscal reach. But you sound like you have a decent grasp on repairs, so it probably will come down to a fiscal decision.
Good call Paul. I'd rebuild it in a heart beat if the savings were there but it'd be crazy to spend the same or more as a new one to rebuild the old if it's only going to last 2 years again. I'm convinced this one's less than 2 years old but I can't find the receipt. Just going to buy the cheapest thing I can with the longest warranty. I'll probably strip the old one far enough to recover the aluminium for scrap.
 

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I've flipped any number of box-store customers, as: The Bitterness of Poor Quality Remains Long After the Sweetness of Low Price is Forgotten.
Might I suggest you look at a Stihl SH56CE or even the 86 with anti-vibe handle, bigger engine than the Ryobi, 2-yr. warranty extendable to 4 with purchase of Stihl Ultra oil or Motomix fuel.
And look at Stihl Motomix or RedMax Maxfuel which saves carb rebuilds/replacements on occasional use products...keeps your machines running and saves on repairs (counter-productive effort as a mechanic, but that's ok).
 

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I've flipped any number of box-store customers, as: The Bitterness of Poor Quality Remains Long After the Sweetness of Low Price is Forgotten.
Might I suggest you look at a Stihl SH56CE or even the 86 with anti-vibe handle, bigger engine than the Ryobi, 2-yr. warranty extendable to 4 with purchase of Stihl Ultra oil or Motomix fuel.
And look at Stihl Motomix or RedMax Maxfuel which saves carb rebuilds/replacements on occasional use products...keeps your machines running and saves on repairs (counter-productive effort as a mechanic, but that's ok).
Thanks for the info Paul. Unfortunately, it's my wife that I have to convince, lol.
 

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Ask her if she wants to keep using the one that doesnt start or get a new one that does?
 
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