Ryobi 40cc anti-vibe saw.

[NOSHARPTOOL]

Bit demoralizing. Got a Ryobi very cheap: cut two small bushes/trees, saw cuts out and won't start. Spent 4 hours, two spark plugs, two different carbs(guy have me an old spare engine with it) and a can of Holtz. Saw has 100psi cylinder pressure,which is enough to get it going on the Holtz, soon as the fuel goes in it floods the plug. Also a strange thing. The carb that was mounted on saw seems to be able to syphon petrol into the cylinder overnight. The spare carb I have drained of fuel until I can get my head around this exercise.

I don't know just not the situation I was hoping for.

 

[Bob Hedgecutter]

100psi is too low and I am willing to bet if you pull the muffler- the piston is scored up.
Does the saw have a purge valve? If someone has been messing with the carbs and swapping things out, the purge valve is probably under constant vacuum and draining the gas tank into the cylinder.
Engine start in a can will ruin 2 strokes.

 

[NOSHARPTOOL]

Thanks for reply. The Holts aerosol specifically says that it contains lubricant so is suitable for 2 stroke engines. I wouldn't know whether they are spinning a yarn or not on this, but I did only run it for fifteen seconds with the engine start.
Saying that there was so much petrol lub mix which had filled the cylinder and that I had drained out, I am hoping that alone would be enough to lubricate cylinder rings.
I only know about the valve inside the primer bulb. My guess is that either you run the engine till the carb is dry, or swap the fuel hoses on the primer bulb so as to pump the petrol in the carb float chamber back into the tank, should you wish to purge the carb of fuel.
My guess is that you are suggesting that the primer bulb will have been pressed too many times causing excess into the carb. There is an overflow on the carb and it appears excess fuel is suppose to vacate the carb and return to the fuel tank. However as this is not happening, perhaps the valve in the primer bulb is allowing fuel to siphon through the carb and into the cylinder.
Gutted that 100psi will not be enough. A couple of videos are telling viewers that something over 90psi for a hedge trimmer will still mean the engine will run. I'll do the compression test again, reason is I see you have to have the throttle open when you attempt this. I probably had the carb on choke when I pulled it.
I agree that most of the compression tests for similar engines are over 110 psi with many reaching 120psi.

I just found this video which makes me chuckle the number of saws he drags out the back of his pickup.

Lastly there is a video explaining that a dirty piston can cause problems, so I might take off the cylinder and look at the piston. Just hope I can make a gasket if the engine is worth saving.

 

[Bob Hedgecutter]

If the saw was messed with prior to you getting it and the hoses are incorrectly installed- rather than purge the carb of air as it is supposed to- it is acting as a fuel pump.
Excessive rope pulling in an effort to start the saw will also lead to flooding and possible hydro locking of the crankcase.
120psi is about the minimum level I will tolerate- but a lot depends on the gauge you use as to the reading you will get- most gauges are not suited to small volume engines and will give untrue low readings.
You do not need to pull the cylinder to check the piston- pull the muffler and look through the exhaust post as you turn the engine over slowly.
If the saw has been run lean, the exhaust side of the piston will be torn up and scoring will be visible on the piston face through the exhaust port.
I suspect this will be your problem- low compression, starter fluid required to start the saw..........

 

[NOSHARPTOOL]

Many thanks again Bob.
I spent an hour going through fundamentals on 2 stroke carbs and they all seem to pull air and fuel from the carb, none of them push it into the priming chamber. So your prognosis that someone had routed the fuel lines wrongly was absolutely correct.

Having now correctly fitted the clear fuel lines to the carb I find the cylinder does not flood. I can start the engine without Holtz, using petrol mix instead. However the old carb is not spraying fuel into the chamber(either correctly or not at all) and I think my best bet is to actually find a replacement.
Looking online so far has not thrown up an exact replacement, but I am wondering if one of those cheap mouldings going for around £20 would fit.

Lastly I correctly checked the compression and lucky for me it is over 120psi now.

I'll keep you posted.

 

[NOSHARPTOOL]

Hi Bob just and update on the RYOBI RCS4040ca engine tuned and running. Finally the carb cleaned through and tuned it with the HL screws.

Further problem now though is the oiler isn't pumping oil onto the chain. Cleaned out the channels to no affect, however thought I would try to remove the clutch see if the oiler is under it. The clutch is a left and thread but doesn't not seem to tap off easily, with the rope inside the cylinder etc. Bit frightened to give it a big wallop.
Tried putting a really light oil in the oil tank in the hope it would run through, this didn't work.
Oh after writing this I have just got it to budge and removed the clutch assembly and the big black backing washer. Looks like there is some sort of cylinder type pump in silver metal screwed down over the crank shaft. I'll take it out tomorrow.

Joe.