Alphadelta
ArboristSite Member
This is meant to be an informative post and save someone time and money. I picked up a MS250C with a Zama carb couple years ago for pretty cheap on account it didn’t run very well. Got it home, cleaned it up, did the typical basic carb clean and tuned it the best I could. But it never really ran right, it was fickle and every time I picked it up I wondered what weird behavior I was going to have to deal with. But it was the backup saw so never investigated further; decided today that needed to change.
Yanked it apart, took the carb out, checked the jets, they all looked decent. Put it back together and yep still runs awful, if it would run at all. Read some forum posts and decided just for kicks before I resigned and had the local shop take a look I would REALLY clean the carb. I took everything off the carb I could without removing roll pins or wrenching on it. Then it sat the ultrasonic cleaner with just simple green and hot water for 10 minutes, pulled it out, blew low pressure air through it, back into the vat for 5 more minutes to finish it off.
Put it back together, did the service manual factory settings for the carb (all the way seated back one turn on both high and low screws) started it and…. It was still running poorly and for some reason while in high idle I hit the primer bulb just because I wanted to see how it acted, it sputtered then settled right down. It runs like an absolute dream! My jaw hit the floor. I have NO idea what pressing the primer bulb did, maybe the diaphragm was stuck in an odd position but I digress. Why after having this saw for 4 years I didn’t spend the extra 1 hour to really clean it is beyond me. I was about ready to write this thing off so -
My point is before you right off your 250 with a Zama carb and start throwing parts and energy into it - really give that carb some love and do your best to clean it out really, really well. Ultrasonic cleaner is your friend, I’ve heard Seafoam works really well. If you don’t want to buy an ultrasonic (or use your wife’s), they sell small carb cleaning needles on Amazon for cheap. Make sure you’re diligent with your cleaning process, go slow, tear it down as much as you can so any contamination inside the carb doesn’t get stuck and your cleaner has access to it. No high pressure air and start with the factory tune settings. I could have sworn I did a decent cleaning job when I first bought it and always chalked it up to ghost in the machine. Also check the fuel line into the carb plenty of forum posts about it getting pinched and starving the saw when you go to rev it up.
Hope this helps someone out there who was/is equally frustrated with their 250.
Be safe all.
Yanked it apart, took the carb out, checked the jets, they all looked decent. Put it back together and yep still runs awful, if it would run at all. Read some forum posts and decided just for kicks before I resigned and had the local shop take a look I would REALLY clean the carb. I took everything off the carb I could without removing roll pins or wrenching on it. Then it sat the ultrasonic cleaner with just simple green and hot water for 10 minutes, pulled it out, blew low pressure air through it, back into the vat for 5 more minutes to finish it off.
Put it back together, did the service manual factory settings for the carb (all the way seated back one turn on both high and low screws) started it and…. It was still running poorly and for some reason while in high idle I hit the primer bulb just because I wanted to see how it acted, it sputtered then settled right down. It runs like an absolute dream! My jaw hit the floor. I have NO idea what pressing the primer bulb did, maybe the diaphragm was stuck in an odd position but I digress. Why after having this saw for 4 years I didn’t spend the extra 1 hour to really clean it is beyond me. I was about ready to write this thing off so -
My point is before you right off your 250 with a Zama carb and start throwing parts and energy into it - really give that carb some love and do your best to clean it out really, really well. Ultrasonic cleaner is your friend, I’ve heard Seafoam works really well. If you don’t want to buy an ultrasonic (or use your wife’s), they sell small carb cleaning needles on Amazon for cheap. Make sure you’re diligent with your cleaning process, go slow, tear it down as much as you can so any contamination inside the carb doesn’t get stuck and your cleaner has access to it. No high pressure air and start with the factory tune settings. I could have sworn I did a decent cleaning job when I first bought it and always chalked it up to ghost in the machine. Also check the fuel line into the carb plenty of forum posts about it getting pinched and starving the saw when you go to rev it up.
Hope this helps someone out there who was/is equally frustrated with their 250.
Be safe all.