ms250 carb question

[HarleyT]

Yeah, Tillotson makes a good carb. I wish we could get them over here easier.

 

[SteveSr]

No, it's a zama.

Just put a fully adjustable genuine Walbro WT-215 on it. Should be available on Ebay. You may have to change the rubber adjustment screw grommet to fit the new carb.

 

[Nathan Graff]

Ok. I have changed the carb. Won't start. I've checked the spark. It has spark. It is getting gas, as it's coming out the muffler. Compression is a bit over 150psi. I took the filter off, so I think it's getting air. So, I'm wondering, what am I missing?

 

[SteveSr]

It is getting gas, as it's coming out the muffler.

You flooded it! These can be very easy to flood as you don't always hear the "pop" It may just tug on your arm a bit. When you feel this just raise the lever 1 notch to start position and pull until it starts. There are MULTIPLE threads on this forum about this issue.

BTW, which carb do you have on it?

 

[Nathan Graff]

You flooded it! These can be very easy to flood as you don't always hear the "pop" It may just tug on your arm a bit. When you feel this just raise the lever 1 notch to start position and pull until it starts. There are MULTIPLE threads on this forum about this issue.

BTW, which carb do you have on it?

I've never heard this one pop. I thought gas coming out the muffler was a sign of a bad carb. Right now, she wears a walbro 215 clone. I might put the original back on and save the clone for the ms170 as a spare.

Thx for the response. I'll give that a try. The saw does tend to tug on your arm after 2-3 pulls.

 

[Nathan Graff]

Ok, so I tried the pull till it tugged and then switch to half choke. Must have pulled 100+ times on half choke after the tug, and got nothing.... Am I still missing something?

Tug happened after 2 pulls on full choke.

 

[SteveSr]

Ok, so I tried the pull till it tugged and then switch to half choke. Must have pulled 100+ times on half choke after the tug, and got nothing.... Am I still missing something?

That "half choke" (i.e. Starting Position) is really NO choke and part throttle assuming that everything in the linkage is working correctly. Pull the AF cover and check to make sure that this is actually happening. The choke is pretty easy to check. Blip the throttle trigger and verify that the throttle snaps back to idle position. The lever should also move up a notch at the same time.

BTW, what did the plug look like after all of this? Was it wet or dry?

[QUOTE="Nathan Graff, post: 6944794, member: 162288"Tug happened after 2 pulls on full choke.[/QUOTE]

That's about right.

Still could be a carb issue. Chi-com carbs are unpredictable. May work may not. I won't use them. Not good to troubleshoot a possible carb issue by using another dodgy carb!

 

[Nathan Graff]

The linkages seem to be working properly as stevesr described. Plug was wet.

I do have the genuine stihl carb that I put on dad's ms170. I can probably take that one off, and see if it works on the 250.

 

[SteveSr]

The linkages seem to be working properly as stevesr described. Plug was wet.

Still too much gas getting through carburetor.

I do have the genuine stihl carb that I put on dad's ms170. I can probably take that one off, and see if it works on the 250.

I don't know if this is advisable as the 170 carb is non adjustable and will likely not flow enough gas to keep the 250 from burning up. The way this works the other way around is that the WT215 is fully adjustable and can therefore be dialed back to run the 170.

 

[Nathan Graff]

I put a WT215 into the ms170. But I moded the linkages a bit so I don't have to completely disassemble the handle of the saw to get it back out.

 

[Okie294life]

Have you checked the L/H idle screws to make sure they are 1.25 turns out? What kind of mix are you running is it factory stihl mix at normal concentration with no ethanol?
If it’s still getting too much gas then it’s probably a bad metering valve on the China carb. Sounds like it’s flooded though. May want to take the plug out and let it dry, and while the plugs out turn it upside down and crank it several times at low throttle to see if a bunch of gas comes out.

I don't know if this is advisable as the 170 carb is non adjustable and will likely not flow enough gas to keep the 250 from burning up. The way this works the other way around is that the WT215 is fully adjustable and can therefore be dialed back to run the 170.[/QUOTE]
Have

 

[Nathan Graff]

Have you checked the L/H idle screws to make sure they are 1.25 turns out? What kind of mix are you running is it factory stihl mix at normal concentration with no ethanol?
If it’s still getting too much gas then it’s probably a bad metering valve on the China carb. Sounds like it’s flooded though. May want to take the plug out and let it dry, and while the plugs out turn it upside down and crank it several times at low throttle to see if a bunch of gas comes out.

I don't know if this is advisable as the 170 carb is non adjustable and will likely not flow enough gas to keep the 250 from burning up. The way this works the other way around is that the WT215 is fully adjustable and can therefore be dialed back to run the 170.

Have[/QUOTE]
I used the H/L adjustments on the side of the saw. I think it's .75 high and 1 low. Or it could be the other way around.

I'll give drying the saw out a go.

As for the gas, it's what the saw was bought with. I didn't see the seller personally as I bought it through proxy. My friend that picked it up said that she saw the saw started and running and it ran, idled, and reved for 10 min which she set a timer to know how long. (I had sent here to get the MS200 the guy had for sale, not the 250) She said that it was a bit difficult starting. I'll give tossing the gas out and putting newer fuel into it a try.

I'm also wondering if it's not sparking under compression. I've heard of, but never experienced, plugs that would spark under normal atmosphere, but not under compression in the cylinder.

Also wondering if it's the coil...

 

[Okie294life]

Have

I used the H/L adjustments on the side of the saw. I think it's .75 high and 1 low. Or it could be the other way around.

I'll give drying the saw out a go.

As for the gas, it's what the saw was bought with. I didn't see the seller personally as I bought it through proxy. My friend that picked it up said that she saw the saw started and running and it ran, idled, and reved for 10 min which she set a timer to know how long. (I had sent here to get the MS200 the guy had for sale, not the 250) She said that it was a bit difficult starting. I'll give tossing the gas out and putting newer fuel into it a try.

I'm also wondering if it's not sparking under compression. I've heard of, but never experienced, plugs that would spark under normal atmosphere, but not under compression in the cylinder.

Also wondering if it's the coil...[/QUOTE]
Best guess is gas that’s in it is crap, with too much mix and the saw won’t rip because because it’s set to run with normal gas like it’s supposed to run.

 

[Nathan Graff]

Ok, I put fresh gas in. saw will start and run now, but I can't get it to rev without bogging down during a period of reving. Adjusting the H/L screws didn't seem to help. Right now at 1 1/4 turns out each.

 

[Okie294life]

Ok, I put fresh gas in. saw will start and run now, but I can't get it to rev without bogging down during a period of reving. Adjusting the H/L screws didn't seem to help. Right now at 1 1/4 turns out each.

Carb is crap or you got some bad fuel lines-filter. I’d start look at the fuel lines to make sure there’s no holes or breaks in them. Sounds like you aren’t pulling enough gas through the carb like a bad screen, or sucking air somewhere. I would bet it’s both. If you find that your fuel lines are thrashed, do yourself a favor and take that carb apart and clean the screen inside the carb because almost undoubtedly there’s some trash in there.

 

[Nathan Graff]

Carb is crap or you got some bad fuel lines-filter. I’d start look at the fuel lines to make sure there’s no holes or breaks in them. Sounds like you aren’t pulling enough gas through the carb like a bad screen, or sucking air somewhere. I would bet it’s both. If you find that your fuel lines are thrashed, do yourself a favor and take that carb apart and clean the screen inside the carb because almost undoubtedly there’s some trash in there.

I'll have a look at the fuel lines and the carb. One clarification, as the saw leans out, shouldn't it rise in rpm before dropping?? This one runs up to what you'd think is the correct rpm for a bit, then slowly starts falling off without a sound of rpm increase. Then the trigger is let off, the saw idles fairly high for a few seconds.

 

[CausticUC]

I'll have a look at the fuel lines and the carb. One clarification, as the saw leans out, shouldn't it rise in rpm before dropping?? This one runs up to what you'd think is the correct rpm for a bit, then slowly starts falling off without a sound of rpm increase. Then the trigger is let off, the saw idles fairly high for a few seconds.

If you are fuel starving, no. If you have enough air and fuel to mix higher, yes. Like a lighter running out of fuel, the flame gets smaller and wont spark in drafty areas.

Dropping back down to idle you are closing off air and making a better combustion mixture with an adequate amount of fuel.

I had similar behaviour with a split fuel line, when the saw was warm the pressure as the throttle opened would cause it to leak and bog down.

 

[Nathan Graff]

If you are fuel starving, no. If you have enough air and fuel to mix higher, yes. Like a lighter running out of fuel, the flame gets smaller and wont spark in drafty areas.

Dropping back down to idle you are closing off air and making a better combustion mixture with an adequate amount of fuel.

I had similar behaviour with a split fuel line, when the saw was warm the pressure as the throttle opened would cause it to leak and bog down.

ok. That's exactly what's happening. It ran just fine cold. I'll get a new fuel line and filter, and maybe a new breather and hose as well.

 

[SteveSr]

Amazing what fresh (from the pump!) gas can do!

I'll get a new fuel line and filter

These fuel lines are prone to leak at the sharp bend at the top of the tank. Also as mentioned pull the pump side of the carb (single BIG screw) and check the screen for debris.

maybe a new breather and hose as well.

This isn't your problem but if it is crumbling then it should be replaced. It is just regular 3.1x5.7mm fuel line.

 

[stihldragon]

Is it worth buying a real walbro for this saw, or is a clone good enough? I know there are some saws that I've read to not bother with the clones. Is there a good place to buy a clone?

Short story on the saw. I had a friend get it. She said the saw was hard starting, but it idled well and ran well for 10 minutes that were counted by a timer.

I got it yesterday. The saw wouldn't start no way, no how. Today, I fooled around with it by taking the carb out, and cleaning the outside, and popping off the limiter cap. Retuned the saw a bit. Saw will now start, but will not idle. If one lets off the throttle, the saw just dies. Adjusting the low speed jet does nothing. Saw runs on fast idle, and full throttle, but smokes like crazy.

Took the muffler off. Piston is not scored that I could see. Can see the machining marks the whole way across. Compression is 135 psi. Fuel is slobbering out the muffler. Spark arrestor isn't dirty that I could see. Just a very small bit of carbon build up in one area. If it hasn't ever been cleaned, the saw has hardly been used in it's life. The spark arrestor actually looks fairly new. It doesn't have a burned look to it like it's been torched off.

It's definitely worth buying an oem carburetor because you know for certain that it's right. Some aftermarket carbs are good and some are not. it's a Gamble. When I rebuilt my 025, I put an aftermarket carburetor on it, and it had starting issues. Ran good and idled good, but on a hot start, it took five pulls on half choke. I'm not going to use that carb on my work. My 025 is still down until I get another chance to work on it

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