MS290 will not start

[dallypost]

Getting closer

I went through the carb and got it back to gather, replaced the fuel line. It now starts very easy but does not want to stay running. It bogs down when I hit the throttle and dies if I let it idle all the way down. I think now that I just need to tune the carb. My users manual says 3/4 turns out for H and 1/4 turn for L. That is how the saw is set up now.

I am making some assumptions here so please tell me if I am wrong.

1. If I turn either H or L below the recommended settings, I will be running too lean and damage the engine, is this correct?
2. If H is for High RPM tuning and L is for low RPM tuning, which one do I adjust to make it accelerate with out bogging?

Thanks everyone.

 

[RAMROD48]

I went through the carb and got it back to gather, replaced the fuel line. It now starts very easy but does not want to stay running. It bogs down when I hit the throttle and dies if I let it idle all the way down. I think now that I just need to tune the carb. My users manual says 3/4 turns out for H and 1/4 turn for L. That is how the saw is set up now.

I am making some assumptions here so please tell me if I am wrong.

1. If I turn either H or L below the recommended settings, I will be running too lean and damage the engine, is this correct?
2. If H is for High RPM tuning and L is for low RPM tuning, which one do I adjust to make it accelerate with out bogging?

Thanks everyone.

need to adjust both...

If you have removed the limiter caps, continue, if not....remove and then continue...

Start with both screws at 1 turn open from a gently seated needle


Now raise the LA screw until motor wants to turn the clutch

Now slowly turn low speed in, raising the RPM's until saw wants to fall on its face lean, back out 1/2 turn...make sure, saw accelerates without bogging

Now you can adjust the idle to idle the saw like normal

Set high speed to a point where it 2cycle/4cycles...until you can get it to someone with a tach, unless you have one then set RPM's to13,500-13,800 and get cutting your wood...

If running a short bar, I like to back that RPM down to 13,200...that's just me though...

But like I said, remove the limiters first....

 

[adkranger]

That's all good info above. The service manual calls for initial settings at 1 turn L and 1 turn H to start. It also states the WOT rpms at 12,500(MS290), ms310/390 @ 13,000, not saying the previous post is inaccurate but it is not what's in the manual. Probably where the OP wants to stay till he gets more experience.

Sounds like the L setting is too lean. Start with 1 turn and go from there.

edit: "2. If H is for High RPM tuning and L is for low RPM tuning, which one do I adjust to make it accelerate with out bogging?"

Yes. You need to set the L needle first for easier starting, stable low speed and acceleration. With it being lean you get that flat spot (bog) in the acceleration curve. Start with 1 turn. Start saw, it should idle and accelerate w/o hesitation. If not, make small adjustments until you do (1/8 turns or so). Then you can adjust the H (should be 1 turn out to start). Make sure you have a bar and chain installed and open the throttle to WOT. If it accelerates smoothly to the top and burbles(aka 4 strokes) you are good for ear tuning. If it just screams at WOT probably too lean, turn out H slightly until it burbles. If it struggles at WOT, and smokes a bit, too rich turn H in slightly. Make small adjustments at a time till you get the desired output. Then set it in some wood at WOT it should be smooth at WOT (no burble). There are a few videos out there that are very good so you can hear what sound you're looking for.

Oh, just want to add. Do not hold saw at WOT continuously without a load to make the H adjustments. A few seconds each time is not bad, just don't sit there with the saw at WOT for extended periods of time unloaded (not in wood).

 

[dallypost]

If you have removed the limiter caps, continue, if not....remove and then continue...

I found some red plastic things on the carb where I expected to find typical spring tensioned needle valves. I was not quite sure of what to do with these because I normally remove and clean the needles and ports when I go through a carb. I could see no easy way to remove them without damaging them so I left them alone. Are these the limiter caps that you are talking about? When you say remove, do you mean remove and discard or will I have to replace them after the adjustment?

 

[RAMROD48]

I found some red plastic things on the carb where I expected to find typical spring tensioned needle valves. I was not quite sure of what to do with these because I normally remove and clean the needles and ports when I go through a carb. I could see no easy way to remove them without damaging them so I left them alone. Are these the limiter caps that you are talking about? When you say remove, do you mean remove and discard or will I have to replace them after the adjustment?

Yes thats them...

they make a tool that you can remove them with if you want to reinstall them, but once you learn how to adjust a carb. you really dont need them...

But dont loan the saw out...Also this will void the warrenty if its still in the warrenty period...But I think you said it was 2 years old...

 

[RAMROD48]

That's all good info above. The service manual calls for initial settings at 1 turn L and 1 turn H to start. It also states the WOT rpms at 12,500(MS290), ms310/390 @ 13,000, not saying the previous post is inaccurate but it is not what's in the manual. Probably where the OP wants to stay till he gets more experience.

Sounds like the L setting is too lean. Start with 1 turn and go from there.

edit: "2. If H is for High RPM tuning and L is for low RPM tuning, which one do I adjust to make it accelerate with out bogging?"

Yes. You need to set the L needle first for easier starting, stable low speed and acceleration. With it being lean you get that flat spot (bog) in the acceleration curve. Start with 1 turn. Start saw, it should idle and accelerate w/o hesitation. If not, make small adjustments until you do (1/8 turns or so). Then you can adjust the H (should be 1 turn out to start). Make sure you have a bar and chain installed and open the throttle to WOT. If it accelerates smoothly to the top and burbles(aka 4 strokes) you are good for ear tuning. If it just screams at WOT probably too lean, turn out H slightly until it burbles. If it struggles at WOT, and smokes a bit, too rich turn H in slightly. Make small adjustments at a time till you get the desired output. Then set it in some wood at WOT it should be smooth at WOT (no burble). There are a few videos out there that are very good so you can hear what sound you're looking for.

Oh, just want to add. Do not hold saw at WOT continuously without a load to make the H adjustments. A few seconds each time is not bad, just don't sit there with the saw at WOT for extended periods of time unloaded (not in wood).

Yeah thats probably better but I have not seen many out of the box that even come close to this low of an RPM range...I always give up to 300 rpms difference...So 12,500 to 12,800 willbe fine...

 

[RAMROD48]

need to adjust both...

If you have removed the limiter caps, continue, if not....remove and then continue...

Start with both screws at 1 turn open from a gently seated needle


Now raise the LA screw until motor wants to turn the clutch

Now slowly turn low speed in, raising the RPM's until saw wants to fall on its face lean, back out 1/2 turn...make sure, saw accelerates without bogging
Now you can adjust the idle to idle the saw like normal

Set high speed to a point where it 2cycle/4cycles...until you can get it to someone with a tach, unless you have one then set RPM's to13,500-13,800 and get cutting your wood...

If running a short bar, I like to back that RPM down to 13,200...that's just me though...

But like I said, remove the limiters first....

ALSO, I should have said....

Turn in the low speed screw until it falls off lean, then go back to the high point....now open 1/2 turn...

 

[adkranger]

Yeah thats probably better but I have not seen many out of the box that even come close to this low of an RPM range...I always give up to 300 rpms difference...So 12,500 to 12,800 willbe fine...

Agreed. Considering he'll be ear tuning most likely, unless his ear is better than mine, a few hundred R's not going to make a difference.

 

[dallypost]

It's alive

Hey everyone, I got her tuned up and running. Crazy thing is that it sat there and idled fine for several minutes and then died. Now it will fire off when I choke it but immediately die when I go into the normal run position. I think that maybe there was a piece of debris in the new fuel line or maybe maybe somewhere in the carb that I missed. I guess I will take it a part for a final cleaning.

But the good news is that I think I should be able to get it from here. I really appreciate those of you who patiently answered my endless chain of dumb questions.

One last silly question. There is another line that comes off of the upper left corner of the fuel tank, wraps around the top of the carb and goes into a widget that hangs from the rubber adjustment screw boot. Is that just a vent and breather?

Thanks again,

Lance

 

[Saw Dr.]

ALSO, I should have said....

Turn in the low speed screw until it falls off lean, then go back to the high point....now open 1/2 turn...

I think 1/2 turn is a bit excessive. Maybe 1/4. You want to richen it up a tad from the highest setting.

 

[Saw Dr.]

Hey everyone, I got her tuned up and running. Crazy thing is that it sat there and idled fine for several minutes and then died. Now it will fire off when I choke it but immediately die when I go into the normal run position. I think that maybe there was a piece of debris in the new fuel line or maybe maybe somewhere in the carb that I missed. I guess I will take it a part for a final cleaning.

But the good news is that I think I should be able to get it from here. I really appreciate those of you who patiently answered my endless chain of dumb questions.

One last silly question. There is another line that comes off of the upper left corner of the fuel tank, wraps around the top of the carb and goes into a widget that hangs from the rubber adjustment screw boot. Is that just a vent and breather?

Thanks again,

Lance

Yes that is the vent line and valve.

 

[Fish]

When you go back into the carb, remove the lever/spring/needle, and
hold up to a light, then blow it out, look again, and visually verify that the
passage is clear.

 

[andrethegiant70]

Being fairly new to saw repair means that even the simple stuff can be a bit difficult. There's a new language to learn and an understanding of the machinery to be had. You should take the opportunity just to do some searches and reading to get familiar, it will help a lot.

Honestly, it sounds to me like you need to kit the carb... new diaphrams. It's $10-13 for the kit. A good tune after that. I very much doubt there is anything wrong with this saw that some fuel system tinkering will not solve.

Good luck!

 

[RAMROD48]

I think 1/2 turn is a bit excessive. Maybe 1/4. You want to richen it up a tad from the highest setting.

Had too many saws that 1/4 wasnt enough, I started going 1/2 on everything and its working so I just run with it...

 

[dallypost]

Honestly, it sounds to me like you need to kit the carb... new diaphrams. It's $10-13 for the kit. A good tune after that. I very much doubt there is anything wrong with this saw that some fuel system tinkering will not solve.

Sorry if I have been unclear. I know that it is easy to get lost in a long thread like this. Here is the readers digest version of what has happened so far.

1. saw would not start
2. cleaned air filter... no joy
3. replaced plug and fuel filter... no joy
4. replaced fuel line and put a kit in carb
5. started and tuned saw
6. saw ran great and idled for several minutes and then died.
7. saw will start with choke on and dies when I move it to the normal run mode.

I am now planning to go back into the carb for a final cleaning because I suspect that I accidentally left a bit of junk in the carb or that there was something in the new fuel line that washed into the carb.

I will let you know what I find.

 

[RAMROD48]

Sorry if I have been unclear. I know that it is easy to get lost in a long thread like this. Here is the readers digest version of what has happened so far.

1. saw would not start
2. cleaned air filter... no joy
3. replaced plug and fuel filter... no joy
4. replaced fuel line and put a kit in carb
5. started and tuned saw
6. saw ran great and idled for several minutes and then died.
7. saw will start with choke on and dies when I move it to the normal run mode.

I am now planning to go back into the carb for a final cleaning because I suspect that I accidentally left a bit of junk in the carb or that there was something in the new fuel line that washed into the carb.

I will let you know what I find.

How does the compression feel now?

 

[sefh3]

When you first tore this saw down, what did the air filter look like? Was it full of junk? How was the fuel line? I know you replaced it but did it have a hole in it?

 

[sefh3]

Did you replace your impulse line also or just fuel line?

 

[dallypost]

How does the compression feel now?

I am pretty sure that compression is fine. I honestly think that it is a carb issue. I did a lot of chipping and scraping to get all the hardened junk out of it. It is very possible that something was left inside. It was also kind of tricky to thread the intake end of the fuel line into the top of the tank. It is possible that I picked up a bit of gunk while doing that. Before I jump to any other possibilities, I want to eliminate this probable issue.

 

[adkranger]

Eliminate the easy and/or known first...... = a good plan in my book.