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Discussion Starter · #1 ·
Ryobi 725r, ran out of fuel,very fast idle. Could not restart, replaced brittle fuel lines, 1/8 inch ID by the way. After several weeks went by I tackled it again,got it to run good but hard to start, kept finding plug wet. After drying it off it cranked OK. HAd the same old problem of which line went to the primer and where. Now 1 push on the primer,choke on and it fires right up but more than 1 prime and it's flooded. Is it possible that I have a fuel leak thru the carb into the cyl albiet a Small one?
 

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Yes, it's possible you have a small leak or a stiff metering diaphragm causing the carburetor to leak. You may also have the primer hooked up wrong, pushing fuel into the carburetor, rather then drawing the fuel through the carb. Make sure the line coming from the carburetor to the primer is on the suction side of the primer, not the output side. If the primer is hooked up wrong, it can cause the carburetor to flood, and affect the running.
 

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Discussion Starter · #3 ·
When I couldn't get it to run, I looked down the carb throat while pushing the primer and saw no fuel entering carb. That's when I swapped the 2 hoses on the primer, now when I push primer I see fuel entering bottom left of venturi. Outside of all that It runs like a champ. I agree that the primer maybe pushing fuel thru the carb.
 

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Technically it's not a primer, but rather a purge pump. It's intended purpose is to purge the air out of the carburetor and fill it with fuel, to minimize the amount of pulling on the starter to get fuel to the carburetor and start the engine. If fuel is being forced out of the carburetor when the primer bulb is operated, then it's hooked up wrong.
 

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Technically it's not a primer, but rather a purge pump. It's intended purpose is to purge the air out of the carburetor and fill it with fuel, to minimize the amount of pulling on the starter to get fuel to the carburetor and start the engine. If fuel is being forced out of the carburetor when the primer bulb is operated, then it's hooked up wrong.
are we talking about the walbro 188-512 ?

yep i have them memorized
 

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Discussion Starter · #7 ·
Welll the primer might be backa--wards but only have to push it once instead of 10 or more times and it sure starts a lot quicker. I neglected to see what carb number wa on it. Will check it next time I have to mess with it. Thanks for the info though.
 

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Discussion Starter · #8 ·
Well, cranked up Ryobi this am,started easy, idle rpm about 6,000. Didn't even have to use throttle to get revs up. Looks like I'm going to have to rebuild carb. Will have to wait until next month after 55th class reunion. Going to be a lot of driving,1400 miles one way and plan to visit some of the towns I grew up in. Small places with populations of 100 to 200.
 

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Another 725r

New member here, St. Louis area location. I'm not as far along as JEJ. I have a three year old model that sat all winter with gas in it. I assume that is why the primer bulb and tubing all went brittle. Bought a new bulb kit and tried to install it, but discovered that rest of the small fuel lines needed replacement. Now I don't know how it all goes back together. Is there a source with diagrams or pics that show proper assembly?

Related Q: Mine is configured with the string trimmer cutter. Are the rest of the attachments still avaiable, such as the brush cutter?
 

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Discussion Starter · #10 ·
New member here, St. Louis area location. I'm not as far along as JEJ. I have a three year old model that sat all winter with gas in it. I assume that is why the primer bulb and tubing all went brittle. Bought a new bulb kit and tried to install it, but discovered that rest of the small fuel lines needed replacement. Now I don't know how it all goes back together. Is there a source with diagrams or pics that show proper assembly?

Related Q: Mine is configured with the string trimmer cutter. Are the rest of the attachments still avaiable, such as the brush cutter?
Tro Bilt acessories will fit.
 

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Yes, Troybilt attachments will work on most Ryobi trimmers. Troybilts parent company MTD purchased Ryobi a few years ago.
 

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dlk6354;
First welcome to the forum, second, I also am in St Louis, PM me if you dont get the trimmer going;

Now, The cycle for fuel supply is, from the tank through the carb an back to the tank.
Have a good one. Geo
 

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Discussion Starter · #13 ·
Well , took carb off today , as far as I can tell it is a walbro WT526. Haven't taken the carb apart yet. Is there anything in particular I should be looking for as it ran like wide open with no throttle but it would rev higher with the throttle. I probably could have revd it beyond its limits. I have rebuilt quadrajet carbs 35 years ago and they seemed simple compared to the illustrated parts breakdown on walbro's website. Any tips?
 

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Well, cranked up Ryobi this am,started easy, idle rpm about 6,000. Didn't even have to use throttle to get revs up. Looks like I'm going to have to rebuild carb. Will have to wait until next month after 55th class reunion. Going to be a lot of driving,1400 miles one way and plan to visit some of the towns I grew up in. Small places with populations of 100 to 200.
a high idle means either the idle screw is set on the high side or you have an air leak. high idle screw is not totally bad thing... air leak is.
 

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Discussion Starter · #15 ·
Well , got a new NOS ebay carb. Installed no start. Put new parts on old carb and runs ok. Looked like maybe the diaphragm for the metering rod might have been leaking. Got my fingers crossed. Also hooked the primer system up correctly. Bought clear fuel line so you can see which direction fuel goes when priming.
 

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Discussion Starter · #16 ·
More bad news, after running fine for a couple of weeks, it wouldn't start today. Noticed a lot of air bubbles being purged back to Tank.Fiannaly pulled plug, bone dry , no fuel. After much begging engine started but quit right away. Going to try to get a diaphram and gasket kit. Seems like the metering diaphram might have had fuel on both sides.
 

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unless i am thinking of a differet part the metering diaphram should have gas on one side and open to a space that has a hole in the covering to normal pressure air.
 

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Discussion Starter · #18 ·
Trimmer worked fine for about a week.then no start. Installed gasket/diaphram kit, still no start, will run when put gas into carb. About at wits end. Does the same thing with replacement carb.
 

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There may be an air leak into the crankcase, either the gaskets that seal the crankcase cover and or cylinder, or possibly the lower seal.
 
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