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Discussion Starter #1
When I bought my house this past fall, an IDC 580 Supreme string trimmer came with it. I have never heard of IDC before then and I have no other information about it other than it's old and I think IDC was acquired through several transactions to what is now Ryobi. I have no literature or manuals.

The trimmer doesn't run very well. It idles fine, but when you hit the throttle the engine bogs, smoke rolls out the back and the head doesn't spin up very quick. I get along by "goosing" the throttle several times to spin the head up so the engine can get to full throttle without bogging. At the end of a 10-15 min. run, the muffler shield is DRIPPING with 2-cycle oil (ratio 50:1).

I'm guessing this is a fuel delivery/carberator problem as the old spark plug was carboned and wet after running. Based on my description above, is there an easy fix? (fuel adjustment, carb rebuild, etc.) I already replaced the plug and air filter with limited improvement. I just don't want to get into a $100 repair on a 15 yr. old trimmer when I can buy a nice new one for $150 now in the off season.

Thanks!
 

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Should be a 40:1 mixture, but 50:1 isn't harming anything.
Yes it sounds like it could need a carb rebuild... (new gaskets, diaphragm, torn apart and soaked in carb cleaner for a few hours and all hole blown out)
If it runs, which it does, it has enough compression to run.
If its oil on the muffler, it is running to rich... if it has adjustment needles on the carb which it probably has given its age, 1 to 1.5 turns out from all the way snug on both then try to fine tune.
 

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Discussion Starter #3 (Edited)
bugman said:
Should be a 40:1 mixture, but 50:1 isn't harming anything.
Yes it sounds like it could need a carb rebuild... (new gaskets, diaphragm, torn apart and soaked in carb cleaner for a few hours and all hole blown out)
If it runs, which it does, it has enough compression to run.
If its oil on the muffler, it is running to rich... if it has adjustment needles on the carb which it probably has given its age, 1 to 1.5 turns out from all the way snug on both then try to fine tune.
Thanks for the info. What is my most economic option for buying a rebuild kit or making my own? I just called a local place that works on just about everything and the guy seemed completely uninterested in helping me. I'm guessing I will have to get a sheet of the "make your own gasket" material or "gasket in a tube" (Permatex) from the auto parts store. I just did a seach online and found some guy who makes his own from a cereal box?!?!?! Not sure if that is advised for a carburetor, but was interesting.
 

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As bugman said, it most likely is a carb adjustment.... I would try that first before doing a rebuild. It could be a stuck needle but since you said it idles fine I doubt that is what it is. BTW, Ryobi style engines are now made by MTD and the engine design hasn't changed much from the model you own.
 

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I have a IDC 580 Supreme, they are a workhorse built like a tank and are designed for use with a metal blade(8in 1in arbor). The spool and spool nut have left handed theads(FYI). Check the carb it is probably a Zama or Walbro and carb kits are available. I can't check mine it's down on the farm. Have a nice day. Geo
 

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Dont know how new this unit is,but you should ck and see if it has a spark arrester on muffler,the wire mesh gets all pluged up and makes them run like a carb problem.
 

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Discussion Starter #7
Geo was right, I have a Walbro carb and the thing looks spotless! I found the "H" and "L" adjustment screws as well. I went to my local library last night and have a string trimmer service manual coming to me that covers this model. Hopefully it is a matter of playing with the adjustment. Please keep the info coming! The more I know about this thing, the better!
 

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Possible air leak

You may want to check the (4) screws that hold down the crankcase cover where the carburetor mounts, these sometimes get a little loose and allow the engine to run lean.
 

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hankster said:
As bugman said, it most likely is a carb adjustment.... I would try that first before doing a rebuild. It could be a stuck needle but since you said it idles fine I doubt that is what it is. BTW, Ryobi style engines are now made by MTD and the engine design hasn't changed much from the model you own.
Actually Hank, last I saw, I thought the Ryobi units were now being made by Homelite? At least that is where the Ryobi service site directs for new units.
 

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Discussion Starter #11
Thanks to everyone who responded! I had the day off of work today, so I continued working on several things in my garage. I took the trimmer outside and tried playing with the needle adjustments with no luck, still smoking like crazy and difficult acceleration. I came back inside and removed everything except the carb itself and blasted all of it with carb cleaner. Looking at the mouth of the muffler and the piston, there is a lot of carbon build up. The carb cleaner did a decent job removing most of it but I will probably revisit a couple areas.

I let a few pieces sit in cleaner for a while before putting it back together. I stepped back outside and started it up with the screws out 1.5 turns. Initially, there was no change........smoking and difficult acceleration. Then one time I hit the throttle and the engine instantly revved and died. I restarted and it was like a totally different engine! Idle is smoother with NO smoke and she takes off like a scalded dog when I touch the throttle. She does smoke a little when I initially squeeze the throttle, but I don't think this is avoidable and there is NO smoke once at high RPM. It acted like something was stuck or blocked then suddenly blew open. Whatever the case, I'm excited to have properly running trimmer!!!!

I still have 2 questions:

1. For the fine tuning, where should the limit be set on the "H" and "L" idle screws? "L" - I was able to get it low enough that the trimmer head barely moved. I left it adjusted a little higher to freely spin as the idle was faster but smoother.
"H" - I've read that you want it adjusted so the engine can't over-rev. I'm having difficulty determining where that point is.

2. Is there any harm in running a small amount of fuel system cleaner (e.g. Gumout, etc.) in the fuel mix? This trimmer belonged to the previous home owner and based on the amount of carbon build-up, I would say it has been running rich and been abused for most of its life. Just trying to think of any easy steps I could take to clean things out.

Thanks!
 

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On my 580 and othe 2-cycles I use Chevron Techron fuel system cleaner, (don't waste your money on the cheap stuff) at about 1 part Techron to 4 parts fuel and let it run at idle for 20-30 minutes(don't rev it up or the carbon will come loose in chunks and screw things up) Techron is not recommended for 2-cycles, after it idles a while the nasty black junk will start dripping from the muffler, when finished remove the muffler and burn it out with a torch. The inside of the engine will be spotless. Have a nice day. Geo
 
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