Stihl MS250 Won't Run at Full Throttle

[HarleyT]

I think he works for a Stihl dealer in Fla....

 

[Okie]

Lambs: You may know most of this info already.
If you get some time to search around on computer, I've had real good luck finding good Walbro carb info.
I kinda take the you tube stuff with a grain of salt, sometimes helpful, sometimes way off base.
Here is a link that might help you little bit.
http://wem.walbro.com/distributors/servicemanuals/WTseries.pdf
Keep a heads up and be sure and get the gaskets in proper order when installing a kit.
I've had pretty good luck getting kits from flea bay but every once in awhile the sellers have the wrong kit listed for the Walbro's. (close but no cigar) gaskets not quite right. Some Walbro kits have multiple gaskets and pieces, therefore keep your old gaskets in the carb and compare them to the replacement gaskets for a proper match because it'ormal to have new parts left over in some Walbro kits.

And if you don't have a ultrasonic tank, just use some white vinegar in warm water 50/50 mix just enough that will cover the carb with all the jets removed, pay attention to the L and H jet some are little bit different and use low pressure air not over 20 psi and don't use a rubber tip nozzle so as to seal a air passage when injecting air or you can cause a welch plug to pop or unseal and run a tag wire thru all the little passages. Be careful and don't break off a tag wire in a passage.
I usually sit under a real good light at a work bench and have all the carb parts on a white background.
You have a good chance of repairing the carb with a kit if you have ever seen it run good. If you have never seen it perform properly, Bubba may have already been inside and ???.

This guy here on flea bay is little slow answering email sometimes, but is real good at selling the correct carb kits or can tell you EXACTLY which of his kits is needed, etc.
http://stores.ebay.com/RANDYS-ENGINE-REPAIR

Yes about Ronnie still around, he calls me every once in awhile needing instructions on how to feel his way thru his old FORD truck repairs.

 

[Stillrunner]

Thanks for all the input, I'm the original poster. I was out of town and just got back to my carb issue. I did take the carb apart and soaked it overnight in solvent. Cleaned everything real nice and made sure the metering lever was set to the proper height. I used compressed air at about 20 PSI and blew out every orifice. Put the carb back together and the saw is running fine, starts, idles and revs to full RPM without cutting out.

 

[lambs]

Thanks for all the input, I'm the original poster. I was out of town and just got back to my carb issue. I did take the carb apart and soaked it overnight in solvent. Cleaned everything real nice and made sure the metering lever was set to the proper height. I used compressed air at about 20 PSI and blew out every orifice. Put the carb back together and the saw is running fine, starts, idles and revs to full RPM without cutting out.

What solvents work best for this? I may have to try this again. Thanks!

 

[Stillrunner]

What solvents work best for this? I may have to try this again. Thanks!

Once I took the carb apart, I sprayed all orifices with engine cleaner and let that set for a few minutes. Next I soaked everything, but the gaskets, in mineral spirits, overnight. Finally, I used low PSI compressed air and pushed that through all the orifices. To me, compressed air is a no-no seeing that I ruined another chainsaw carb by blowing it out and then later reading "Never blow air into X orifice." A year ago I had installed new gaskets and cleaned the carb then, too (Stihl MS250). I use this saw a couple times a year and always in April when I go out to do trail work. So it's always around March that I get the saw out from storage and get it ready for a day's work. My metering diaphram cover has a small hole and I read somewhere that it should point a certain direction. When I replaced this cover I made sure I did so, so that it was identical to my $12 carb. As you now have learned, I didn't use any special solvents or technique. I suspect, as others have mentioned, I may have had crud on the H needle or inside that orifice. Here's a good link for info. on the Walbro WT-XXX http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2391633

 

[smokey7]

Sea foam or b 12 chemtool made by barrymans works well for soaking.