Ryobi RBC430SBD

[Stoner]

Good afternoon, how can you find the specifications of this trimmer (4-stroke POWR LT4™ engine, 30cc)? What is the allowable compression? Which direction should the plastic check valves on the hoses be (3 pieces)? The trimmer was mainly operated at 30-35 °C. Do you have a Professional User Manual?

[KE4AVB]

These are the manuals from Ryobi.
https://www.ryobitools.com/support/manuals/details/RY34007

Personally I haven't seen this setup here so I cant answer about the check valves. Being in the breather hose setup I would think face away from the breather though not 100% sure.

Recommend contacting Ryobi on these question since they don't publish service manuals or anyting operator wise in manuals other than the ones above that i know of.

[bgsengine]

Recommend contacting Ryobi on these question since they don't publish service manuals or anyting operator wise in manuals other than the ones above that i know of.

yeah even on the dealer portal they have very little in service info.. took them a couple years before they finally did publish carb adjustment data, after phase 3 came in 2012... basically they are not meant to be serviced, really.. just run em til they quit and throw em away, buy new ones, is the general philosophy, so it is not a surprise that there isn't even a shop manual from them .. possibly because it seems like they change things around every year or so.. so even dealers have trouble figuring out what is the correct parts to get (and often the machines get "rigged" with older version parts just because the "model" (RBC430SBD) is the same.. for correct parts , you got to match up the UT Number (for homelite mostly) or the RY NUMBER (FOR rYOBI MODELS) on the serial number tag .. so you are looking at the right parts for the machine... so if you can get the RY-xxxxxx model number, might be more helpful if anyone here can help.. (I cant , no longer have access to dealer portals)

[Skywatcher]

Hi Stoner

Just took a look at my Ryobi 4-stroke trimmer and as you say, it has 3 check valves in 3 different lines. I know that mine has never been apart except to clean and reseal the sump. For want of a better way of describing them, the check valves have a flat side and a cone side. It would make sense to me that the free flow would be from flat to cone. On the line from the valve cover to the air cleaner, cone towards air cleaner. On air cleaner to crankcase, cone towards crankcase and on valve cover to crankcase, cone towards crankcase.

This would make sense as you'd want crankcase vapors to go to air filter and any oil to be returned to sump. You'd also want oil to drain back from valve cover to sump. As for cylinder compression, check and adjust the valves in needed, then see if the machine runs. KE4 gave you the link to Ryobi manuals, adjust the valves according to page iii of the manual. If the unit still won't run, it's probably easier to just buy a new machine. Hope this helps,

Sky

[Stoner]

Good afternoon, what can the presence (digging up) of oil on a felt insert say?

[Skywatcher]

Hi Again Stoner

A little more information would be very helpful. Is this felt insert on the same machine we're talking about? If so, where about on the machine is this felt insert? And could you expand a little on your term "digging up"? Once we know exactly what part it is you're describing, maybe we can help. All the best,

Sky

[Stoner]

Yes, on the same trimmer, there is a felt insert near the deflector.

[Skywatcher]

Hi Once Again

Please will you be a little more specific as to where about on the machine this deflector is The only thing called a deflector on the illustrated parts list is the grass deflector down by the trimmer head. Is this the deflector you mean, or is there something else you are referring to as a deflector like an exhaust deflector on the engine?

https://www.partstree.com/models/ry-34007-090432017-ryobi-string-trimmer-30cc

All the best,

Sky

[Stoner]

Good afternoon, reference is made to figure 37 (AIR BOX ASSEMBLY). On it, next to the air filter, there is a felt insert.

[Skywatcher]

Hi Stoner

Thanks for the clarification, now I know what you're talking about. I may need some correction here, but I'm guessing that as this is a 4-cycle engine, the felt works to separate the oil droplets from the oil vapour. Any 4-cycle engine will always produce crankcase vapours. In the early days of automobiles, these vapours were simply released to the atmosphere through the road draft tube.

In later years, the positive crankcase ventilation system (PCV) was introduced to burn these vapours through the engine in an attempt to reduce emissions. It is inevitable that some oil droplets will be carried out with these vapours, so a filter was introduced into the PCV system to separate the droplets from the vapour and return the droplets to the crankcase. I'm guessing the felt that you speak of is this filter.

In an earlier question, you were asking about the direction of the check valves. The upper most check valve needs to allow the crankcase vapours into the air filter housing while keeping a slight crankcase vacuum. The felt separates the oil droplets from from the crankcase vapours and release the vapours into the air filter housing to be burnt through the engine. The lower check valve needs to let the separated oil flow back to the crankcase.

I'm guessing that this felt will most probably be damp with oil, but should not be dripping wet. If the felt is dripping wet, either the engine has been turned upside down allowing crankcase oil to flood the crankcase ventilation or the crankcase has been overfilled with oil forcing an oil spray up into the air filter housing. It is also possible that the lower air filter return check valve had been installed the wrong way round preventing the separated oil from draining back to the crankcase. Hope this makes sense to you. If I need to be corrected by other forum members, please feel free to chip in with suggestions. All the best,

Sky