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Author Topic: Need help on Stihl MS250  (Read 2488 times)

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Offline rlueth

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Need help on Stihl MS250
« on: February 13, 2016, 01:00:45 PM »
I just finished putting rings and new seals in a Stihl MS 250 and now it won't start or even fire.  Couple of questions.  I used a drill bit that just fit into the brass "Impulse nipple" on the block wanting to clean it out.  Evidentially it was "necked down" a little as I got some brass chips coming out as I got to the interior end of the nipple. Is that going to be an issue with letting too much air thru as far as starting it ?  Secondly, I put a kit in the carb, used a Zama RB-105 kit.  The parts all fit well but am wondering if this was the correct kit.  The only markings on the carb are "HL lC".  Is this a Zama carb and did I use the right kit.  I can't find any carb identification blurps on the internet.  I'd appreciate any help I can get on these two topics.  Thanks 

Spark and compression is good.  I also rebuilt the carb and MAY have switched the adj needles putting it back together.  One needle is sharp pointed and the other is blunt tipped.  Which is hispeed and which is low speed ?  Thanks

Offline beenthere

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Re: Need help on Stihl MS250
« Reply #1 on: February 13, 2016, 01:32:49 PM »
Welcome to the Forestry Forum.
Many good and knowledgeable people here to help you out.. but does sound like some major changes may have happened.
Click your forum name and you can update your profile with at least your location... helps with a response to know whereabouts you are.   ;)
south central Wisconsin
 It may be that my sole purpose in life is simply to serve as a warning to others

Offline Jiles

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Re: Need help on Stihl MS250
« Reply #2 on: February 13, 2016, 02:31:45 PM »
Impulse enlarging should not be an issue--not getting all the chips out Could!
All the Zama carbs I have "tried" to rebuild had acid etched numbers on the body. Sometimes hard to see or may be rubbed off. Not had a lot of luck with China made Zama carb. In most cases, better to replace at a price close to what a kit cost.
I think your real issue is no spark. Disconnect all wires from kill switch and try , without spark plug, and make sure you use a business card, app. .012 to set air gap between coil and flywheel.
I might add that, for me, this is one of the least liked Stihl chainsaws, because as you have discovered--its not easy to work on.
Satisfy needs before desires

Offline old2stroke

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Re: Need help on Stihl MS250
« Reply #3 on: February 13, 2016, 04:18:57 PM »
If you have verified the saw has good compression, pull the plug, then hold it against the cyl and pull the starter to check for spark.  If you don't have spark it's a coil/wiring problem, if you do have spark, squirt some fuel mix into the plug hole, put the plug back in, hold the throttle open and see if it fires.  If it fires and dies quickly, probably nothing wrong with the ignition and it's time to look at carb issues such as fuel line integrity, choke operation and correct operation of the internal carb parts.
Not too many saws.  Not enough storage space.

Offline joe_indi

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Re: Need help on Stihl MS250
« Reply #4 on: February 15, 2016, 03:20:21 AM »
Forget about the carb for the moment. First thing to check whether you are getting combustion.
Remove the carb. pour a few drops of fuel down the manifold.
Move the master switch to fast idle and try to start it.
If everything else is fine the saw should start up, rev and die when it runs out of the fuel you poured down the manifold.
If it doesn't start, check the ignition.
Are you getting a spark? If yes, are you getting the spark at the correct time?
To check that you will need to remove the flywheel nut and inspect whether the molded key of the flywheel is in the groove on the crankshaft or out of it.
Best thing to do would be to remove the flywheel, align the key with the groove and then tighten down the nut. That way you are 100% sure the flywheel is fitted right.
Try it after all this

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