MS230 Possible air leak

[altatim]

I recently was given a MS230 that would only start on choke so I replace the carb diaphragms and it immediately ran. Since I did that though it seems to be running lean even though I have turned the H screw all the way out. I thought that maybe it was just some debris in the carb so I took it apart and cleaned it all really well, blew out the jets, and put it all together again. Still runs lean on the top end but also tends to choke itself out at idle. No symptoms of typical crank seals as it won't rev while idling and also won't stall when I spray an aerosol toward the clutch side of the saw. Impulse line, fuel lines, and tank vent are all in good shape. Not sure what else to look at.

 

[jltrent]

Try another carb and if all else pressure test.

 

[farmguywithasaw]

I recently was given a MS230 that would only start on choke so I replace the carb diaphragms and it immediately ran. Since I did that though it seems to be running lean even though I have turned the H screw all the way out. I thought that maybe it was just some debris in the carb so I took it apart and cleaned it all really well, blew out the jets, and put it all together again. Still runs lean on the top end but also tends to choke itself out at idle. No symptoms of typical crank seals as it won't rev while idling and also won't stall when I spray an aerosol toward the clutch side of the saw. Impulse line, fuel lines, and tank vent are all in good shape. Not sure what else to look at.

Those Zama cq1 carbs have check valves in them that are notorious for going bad. I would start with a a new carb, or start with a pressure/ vacuum test. Don’t forget to inspect the fuel line either. I did crank seals on my 250 and it ran as you described. It failed a pressure vac test but after the new seals it still ran the same but past another pressure/vac test. It was the carb that was bad. Even after cleaning and rebuilding. I put a walbro of a 025 on it, runs great

 

[SteveSr]

I recently was given a MS230 that would only start on choke so I replace the carb diaphragms and it immediately ran. Since I did that though it seems to be running lean even though I have turned the H screw all the way out. I thought that maybe it was just some debris in the carb so I took it apart and cleaned it all really well, blew out the jets, and put it all together again. Still runs lean on the top end but also tends to choke itself out at idle. No symptoms of typical crank seals as it won't rev while idling and also won't stall when I spray an aerosol toward the clutch side of the saw. Impulse line, fuel lines, and tank vent are all in good shape. Not sure what else to look at.

These tend to leak at the pan/cylinder joint as well as the seals. Definitely pressure test in a bucket of water.

 

[altatim]

I will have to check those suggestions. I haven't ever experienced this before, but then again I haven't been around as long. I might have a spare walbro in a box somewhere that will bolt on if it proves to be the carb itself that is the issue. I know the history of the saw well and I know that it was never abused (my dads old pruning saw new in 2004 I think) so I recall replacing most of the wear items over the years so its not had a hard life by any means. Rebuilt the carb maybe 8 years ago as well and it just started to run "funny" the last few years hence why my dad gave it to me lol

 

[stihltech]

#1 repair on these saws is a new carburetor. Yes, do the vacuum and pressure test first. Just age. 90% of the time it is a carb.

 

[jltrent]

Try and new carb first as said they can look good but are not. It sure saves a lot of time messing with a carb that no matter what you do can't be fixed. Don't buy the Aftermarket junk either as they are half price of a good carb and will never run right.