My Petrol Ryobi chainsaw RCS 3335 is now refusing to run.
It will start on full choke but cuts out immediately after first reving it.
I have stripped and rebuilt the carb many times now.
Blasted out all jets & filters with compressed air.
The only thing I can find possible fault with is the diaphram opperated needle valve on the bottom. The diaphram hardly onens this valve at all. Sould I try very slightly bending the pivot to make it open a bit more. And also where can I buy spares for it?

Dave, January 2012

The original carb on my Ryobi HSC3335 was the Walbro WT673 that has a nozzle type check valve. After a few years I started getting pressure in the fuel tank and the only way I can see that happening is blowback through the carb via the check valve. In the end it wouldn’t run. I eventually bought a new carb online – about $50. It then ran without creating pressure in the fuel tank but would never run on idle well. It stopped running and I couldn’t seem to tune the carb so the saw sat a couple more years. After some searching for equivalent carbs I then bought another new aftermarket A09159 off ebay from Hong Kong for about 1/3 the price. It looked identical to the first replacement and had the same Chinese manufacturer. The saw still wouldn’t run, starting off on the primed fuel before stopping in a few seconds. I realised that the carburettor assembly mount was sloppy because screws holding it to the main engine block were loose. This meant that the pressure from the crankcase to drive the fuel pump diaphragm in the carb was leaking. I tightened up the screws, put the carb back on and fired up second pull and was able to tune up the new carb. A new diaphragm also helped the first replacement run better.

There are other reasons why the diaphragm may not be pumping and you do need to replace them as they get stretched and less flexible. Maybe a new carb is quicker and easier than a carb kit but diaphragms alone are relatively cheap.

The replacement A09159 carbs for the HSC3335 have the V notch in the screw head and not the D as in the original so you will need a new tool if you don’t already have one.

As an aside My Stihl 023C started pressurising the fuel tank a little also, This was solved with a new carb. The original carb was primeable and it seems impossible to find a replacement that has the primer connection so maybe one day I’ll rebuild the old one with a new check valve.

Alec, February 2017

I have the same problems how can i fix it

matty, December 2015

I had the same problem - and found it was not getting any fuel from the carburettor - you can check this by taking the plug out and it will be dry. - and to confirm that it is a fuel problem pour half an eggcup full of fuel directly in the plughole and replace the plug. - it will fire up after a few pulls and run for a few seconds and then die.

ok so it is a problem with the carburettor. - it could be that the inlet valve is set too low - this can be remedied by very slightly bending the little shiny lever (Inside the carb) to let the needle valve have more movement - it only needs a touch....
you may have to adjust the slow running jet and perhaps the fast jet too. These are situated in the extended tube like arrangements along the side of the carb. access to these is easy but you will need to make a tube with a flat on one side to adjust the jets. You will need to turn these jets only a quarter turn or so for a major change in the engine running. The jet adjustments turn very easily and are accessible directly without taking anything apart so it migh be a good idea to do this before you strip the carb out for cleaning and needle valve adjustments.
- My engine now runs very well !! - easy start anytime. Remember - Just adjust yours carefully-

Frank - Kennedy Franklyn, August 2014

Bought this after my McCulloch packed up after 20 years. Sometimes it starts, otherwise it takes ages. I do everything according to the instructions. The mixture is fine, new plug etc; will start after many pulls but then cuts out. When it has worked - when newish - it would never restart when hot. Am going out tomorrow to buy a Stihl.

ACE, March 2014

My Ryobi 3335 is less than 2.5 years old and is doing the exact same as yours- cutting out on the first rev. I changed the spark plug but it made no difference. I've had starting problems since I bought it. I wish I had the time and know how to fix it but I will recycle it instead and buy another make. It will probably cost me more than it is worth to get it fixed by an expert!!

JimmyC, May 2012