# Ryobi 790R



## dhartford (Mar 30, 2008)

Could some one tell me the air gap setting?
Thanks for your time
Don


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## geogrubb (Jul 28, 2006)

Air gap setting for what? 
Have a good one. Geo


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## dhartford (Mar 30, 2008)

Between the flywheel and coil.


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## geogrubb (Jul 28, 2006)

.0010 to .0018
Have a good one. Geo


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## dhartford (Mar 30, 2008)

Thanks Geo

Don


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## Pepo (Apr 29, 2008)

*Ryobi 790r*

Hi, I am new here and have looked at other forums but they seem to be "out to lunch." I have a Ryobi 790r that ran quite good first thing this spring but now is hard to start and when it does it is running rough with little power. I did take the carb off and took the diaphragm side off and blew it our with air. That did not change anything. Did the other side the same way, still no change. I did push the primer bulb while running and it picked up rpms but then quit. Also where can I get a detailed manual for this machine? 
Many thanks for any help.


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## geogrubb (Jul 28, 2006)

Usually the fix is to clean the spark arrestor behind the muffler and check the piston and cylinder walls for scoring, if scored scrap it. Clean the carb in a bath type cleaner then blow out all holes, cracks and crevases with compressed air or brake parts cleaner then install a new diaphram kit using the old metering arm unless it is very worn. Install new fuel lines and filter make sure all bolts are tight and you should be good to go. The site below has a bunch of stuff you can download. Have a good one. Geo
http://www.outdoordistributors.com/ryobi/Ryobi_Parts_Lists.html


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## Pepo (Apr 29, 2008)

*Ryobi 790r*

Thanks for the quick reply. Once I get those suggestions done I will let you know how it all worked out. Thanks from Kentucky


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## geogrubb (Jul 28, 2006)

Your engine probably has either a zama or walbro carb you can get a lot of carb info from their sites, just select the Service/Aftermarket tabs. Have a good one. Geo

www.zamacarb.com
www.walbro.com


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## Pepo (Apr 29, 2008)

*Ryobi 790r*

Hi George et al, well I did take that Zama carb apart, cleaned it in carburetor cleaner, blew it nice and dry and installed new gaskets, diaphragms etc. 
It started quickly but ran a bit rough. The dealer did not have new fuel lines ("on order....blah...blah) and so I blew the fuel lines clear, hoping to clean the small filter in the tank. No change but I did the job that I needed to do and will do more investigating. When the engine runs and I push the primer bulb it will start running smoother and picks up rpms. I am guessing either the needle valve, the sping tension or a plugged fuel filter. I did look at the cylinder wall and surprisingly it still has the cross-hatching of the factory honing! I had to make a new gasket (a job!) for the plastic carb mount and the crank case (I might still have leak there......) My main problem is to find a source for any of the different gaskets etc. for this machine. Any suggestions? I have tried that Outdoors place but they don't go back that far. The clerk at the local dealer told me that he uses some of the "Form-a-gasket" stuff. Any opinions. The whole deal is that I am convinced that if the machine is not in terrible shape it should be able to be made to run. Thanks, take care and have fun. Sorry aboout being long-winded.


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## geogrubb (Jul 28, 2006)

Try www.oscar-wilson.com use the Model Lookup tab and enter 790r which will give you a list of model years, select the parts list to find the part then you can go back to the Check Inventory tab to see if they have it, if not you will at least know the part numbers you need and can search elswhere. Have a good one. Geo


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## Pepo (Apr 29, 2008)

Thanks George for the Oscar Wison link. Ordered some new gaskets etc. Will see how it all works out.


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## Pepo (Apr 29, 2008)

*Memorial day memory*

Well thanks to your help I did get a set of gaskets etc. and decided to tackle that little machine again. Did get the new filter into the tank....wow!...and did get the fuel return installed. The old one had shrunk so bad it let the fuel leak out. Then I went after the "home built" gasket on the crank case and that went well. Thought that I was on a roll so I pulled the cylinder and head off as I had a new gasket. All looked clean and neat. Wiped around with some Acetone and a paper towel and then it happened! The towel hooked the piston ring and snap....two pieces of ring fell to the floor. This morning had an e-mail from Oscar Wilson that a new one was in the mail. What service! Question: should I hone the cylinder wall for the new ring or just leave well enough alone? The cylinder and the piston look ok.


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## geogrubb (Jul 28, 2006)

2-cycle cylinders are pretty difficult to hone because of their design. You should clean the carbon from the piston ring groove, use the broken ring to use as the scraper. It has been brought to my attention that Oscar Wilson's prices are higher than some other online places such as Jack's Small engine, I use Oscar Wilson because I can check their inventory online and they are only a 15-20 minute drive from my house. Have a good one. Geo


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## COMP (Jun 11, 2008)

you get it going ???


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## Pepo (Apr 29, 2008)

Well yes I did get the Ryobi 790r going and it did a prettry good job cutting a bunch of weeds in the "Back Forty." I still wish that it would run a bit smoother. When I get the chance, I will tackle those little plastic covers on the carb adjustment screws. Maybe with a pair of dikes? Take care and have fun.


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