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Ms290 stalls during decelleration.

Post in 'The Gear' started by gzecc, Nov 8, 2012.

  1. gzecc

    gzecc Minister of Fire

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    Any input would be appreciated. I am going to change the fuel pickup and line. But I already did this once before and it didn't solve the problem.
    I am now using the saw a lot since that bit%h sandy visited and its a real pain when the saw stalls.

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  2. Snotrocket

    Snotrocket Burning Hunk

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    Sounds like it needs a carb adjustment.
  3. jrendfrey

    jrendfrey Member

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    my ms 290 will do that also when its cold out and it is first fired up. i have to run it alittle then it will sit there and idle nicely. i agree have the carb adjusted
  4. StihlHead

    StihlHead Guest

    Make sure the air cleaner is not clogged up first. Also make sure that the muffler screen is not clogged up (either will have he same effect).

    Likely the L side of the carb is the issue.

    To tune the carb on a 290 w/o a tach:

    Turn the H & L screws in to seat them lightly, and turn them both out one full turn.

    That's it.

    Or get a good digital tach and tune the 290 carb accordingly:

    Turn the H & L screws in to seat them lightly, and turn them both out one full turn. That is your base starting point.

    Start the saw and run it until it is good and hot. Have some wood handy to do some test cuts with.
    Make sure the chain has the right tension
    Adjust the idle (L/A) screw so that the saw runs at 3.3k RPM
    Turn the L screw in and out slightly to find the maximum RPM
    Adjust the idle (L/A) screw to reset the saw to 3.3k RPM
    Again test that the L screw is set at the highest point for maximum RPM
    Now set the L screw so that the saw runs at 2.8k RPM

    Now that the idle and L screws are adjusted, rev the saw to full throttle (WOT) briefly and adjust th H screw so that the miximum RPM is 12.5k RPM. On a 310 and 390 the maximum RPM is 13.0k. Note that Stihl max RPM settings have an engineered safety margin of 500 RPM, so you can really go to 13k on the 290, and 13.5k on the 310 and 390 if you want. Note that the saw should have a 4-stroke burple at WOT when the saw is not in wood. Once in the wood, the burple sound should clean up. You may want to tweek the H screw at this point to get a good burple WOT that goes away when you bury the bar in wood.

    If the carb has limiter tabs (the little tabs that do not allow you to fully adjust them) you need to use a small screw to pull the plastic adjusting limiter caps out and trim the tabs off so that they can be fully rotated, and put them back into the saw. Once that is done you can tune your saw the way that it was designed to be tuned. The tabs were added more recently to make the saws run leaner than they should, for EPA/smog reasons. Lean running saws tend to burn up faster from overheating.

    If you are not sure about the H screw being too rich or too lean, ease it out 1/16th of a turn to err on the rich side. You can also run the saw in wood for 15 seconds at WOT, and then kill the saw. Let it cool down and then pull the plug. It should be an even tan color. If it is white, the H screw on the carb is set too lean.
  5. StihlHead

    StihlHead Guest

    Also note that your saw carb may just be icing up in the cold weather. The 290/310/390 saws all have summer/winter options on the air filter inlet. Below 40 degrees (Stihl says below 50 degrees, but that is too warm in my experience), you can set the shutter and prefilter to winter mode. This will allow warm air from the engine to be drawn into the intake and help prevent carb icing. To do this, pull the air filter cover and pull off the black prefilter. Then pull the spark plug lead and pull the left-right shutter with a screwdriver and rotate the shutter 180 degrees and snap it in place so that there is an opening on the right side of the plug. Reconnect the spark plug wire and flip the prefilter so that the snowflake symbol is seen and the prefilter screen is down.

    Note that in winter mode more sawdust will get into the air filter, so you will likley have to clean it more often.
  6. MasterMech

    MasterMech Guest

    Will the saw idle normally?
  7. shmodaddy

    shmodaddy Burning Hunk

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    When tuning a saws high side I go wot- lean the saw out till max rpm then fatten her up until she four cycles but cleans up under a load. Not too sure of the blanket carb setting of one screw turn out and good to go. My carb setting changes everytime I cut ( all be it slight changes nothing drastic) due to temperature or barometric differences .

    In my humble opinion great care should be used in tuning a saw. A scored saw from running too lean is an expensive lesson . My advice to you the O.P. is if you understand fully the advice given to you then go for it. If you are unsure of any step in the tuning process do more research or take your saw to your dealer and ask them to show you how to tune correctly.

    Sent from my rooted and eclipse running X2--thanks nitro-- if im posting on here I'm probably supposed to be working! I can't help im addicted to HEARTH.COM!
  8. HittinSteel

    HittinSteel Minister of Fire

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    How does it stall during deceleration?

    I'd turn the L and the H about 1/16 to 1/8 of a turn COUNTERclockwise
  9. gzecc

    gzecc Minister of Fire

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    Thank you, Thank you, Thank you..... Took off those red caps, made the adjustments, now its running good. There is no reason to put those red caps back right. Just put the black boot back on and I'm in business correct?
  10. smokinj

    smokinj Minister of Fire

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    Check your air filter.......
  11. Danno77

    Danno77 Minister of Fire

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    Nah, you can toss them.
    smokinj likes this.
  12. Danno77

    Danno77 Minister of Fire

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    do me a favor and pull your plug after running for a day or two. Something is awry here. It definitely would not be the first saw that needed a carb adjusted beyond the limiter tabs, but at the same time, going into that range should be done so cautiously. As mentioned above, the concern is running too lean. That is the fastest and easiest way to ruin a good engine, it's also the most common reason engines die. But long term running too rich has it's own problems and can certainly ruin a good engine when carbon builds up.
    smokinj likes this.
  13. shmodaddy

    shmodaddy Burning Hunk

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    ^^^^^^^^^^^^^^^^^^^^^
    Agreed:cool:

    Sent from my rooted and eclipse running X2--thanks nitro-- if im posting on here I'm probably supposed to be working! I can't help im addicted to HEARTH.COM!
  14. StihlHead

    StihlHead Guest

    Bad assumption! You need to (follow my instructions above, and) put those limiter caps (trimmed) on the L and H screws back in place. Otherwise they will float around a LOT during operation of the saw. Those caps keep the jets in place so that the carb holds a tune. Otherwise good work.

    As for asking a dealer to show you how to tune a carb, that is not likely going to work unless you know them really well.

    Also the one turn non-tach tuning actually works OK. That is straight out of the Stihl repair manual for the 290. Most of the later model Stihl saws have the L and H turn settings listed on the side of the saws. On any saws with the limiter caps in place, simply turn the H screw all the way until it stops. That is likely to be a tad leaner than you want, but w/o pulling and trimming the tabs, there is little else that you can do. Also note that no dealer or saw shop can leagally tune you saws if the limiter tabs have been trimmed. By law they must replace the limiters with the new ones with tabs and tune the saws as they were at the factory. Same goes for any modified muffler or ported saws. Once you step across to the dark side and modify your newer (after 2000 or so?) saws, you are here to stay.

    May the force be with you...
  15. StihlHead

    StihlHead Guest

    Bad idea. They keep the carb jets in tune with friction against the black rubber boot.

    Not to worry, really. Likely it was his L jet, not the H jet that was the problem for stalling. It may have also been the L/A setting. I have seen this kind of stuff happening on a LOT of Stihl saws I have owned, tuned and/or 'permanently adjusted' for others. The limiter tabs keep saws from being tuned richer, not leaner. If he trims the tabs and turns the jets out too far, it will be on the rich side, not to the lean. That is by design, as the EPA wants leaner, not richer running saws. So they mandated the tabs. You the sawyer and saw owner want a richer running saw (not overly rich, just richer than "EPA-lean"), and in order to do that you have to trim the limiter tabs. If you follow the methods I have listed above with a good tach, you will not run too rich or too lean. You can always pull and read the plug as I recommended above, after a good long pull on the wood at WOT.

    I would argue that engines running lean are the distant second most common reason why 2-stroke saws die. The most common is straight gassing them (by far). ;)

    As for carb tuning saws in general, lean running will certainly overheat your saw engine and it will fry in time, or even in a hurry, depending. Running too rich will gunk it up with carbon. Use good gas and 100% synthetic FC/FD rated premix oil and the carbon buildup will likely not be a problem. There are many ways to run a saw too lean (or too rich) after a perfect carb tune and not know that you are doing it. One is to tune your saw with a clogged up air filter or muffler screen and then clean them after you have tuned the saw. That will allow more air flow and result in running them leaner than intended. Another way to run your saws lean is to let them run out of gas all the time. For a minute or so at the end of a tank of gas, there will be less gas available as it sloshes around in the tank and the saw will run at higher RPM. For that reason I like clear gas tanks so I can fill the saw before it gets to that point. It is subtle, but over time doing that all the time can damage an engine. You also want to tune your saw with the bar and chain that you will be running. If you put on a longer bar you need to re-tune your saw, as it will likely run at a lower RPM at WOT with the added friction. That is not a bad thing, per se, but if you do the opposite and put on a shorter bar, you need to retune the saw to keep it from over-revving. Another reason I have seen saws run lean is if they are tuned at a higher elevation and then used at a lower elevation. That is actually pretty common around here where I am in the Cascades. More air at lower elevation means running leaner. Tuning at a lower elevation and running it higher will cause it to run rich. We are talking over 1,000 ft change in elevation here. There is about a 3% drop in O2 per 1,000 ft of elevation. That can be significant if you tune your saw in Portland (200 ft) and cut wood up around Government Camp (at 4,000 ft). Lastly I noticed that when I flipped from Castrol FB premix oil to Mobil 1 and later to Elf 100% synthetic oil my WOT revs went up in my saws. I had to retune them when I changed over. More subtle stuff, but it happens.
  16. shmodaddy

    shmodaddy Burning Hunk

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    Lots of good info there!

    Sent from my rooted and eclipse running X2--thanks nitro-- if im posting on here I'm probably supposed to be working! I can't help im addicted to HEARTH.COM!
  17. HittinSteel

    HittinSteel Minister of Fire

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    It is best if you can get the caps back on (cut the limiter ears off with a razor) but if you can't, just monitor the way your saw is running by ear. I don't have limiter caps on any of my saws and have never had a problem. They are nice to have though to guide the screwdriver to the needle.
  18. gzecc

    gzecc Minister of Fire

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    Update, Unfortunately my 290 is still stalling upon letting off the trigger. It revs good, but after maintaining high revs, then letting off the trigger, it stalls. I've made multiple adjustments to L H and LA.
  19. MasterMech

    MasterMech Guest

    Adjust the LA so that the chain starts to rotate at idle. Does it still stall? Don't forget to reset the LA back to normal afterwards.
  20. gzecc

    gzecc Minister of Fire

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    That was the last adjustment I made, then put the red plugs back in.
  21. basod

    basod Minister of Fire

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    Maybe a stupid question..
    Does the 290 have a throttle stop adjustment?

    I had a saw that acted like this just before the cyclinder was completely torched(stupid 2 gallon gas can;em)
  22. Danno77

    Danno77 Minister of Fire

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    I might be missing it, but did you say anything about your air filter? is it clean?
    smokinj likes this.
  23. gzecc

    gzecc Minister of Fire

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    I did clean the air filter with compressed air. If you hold it up to light you can see the light passing through.
    I don't know about a throttle stop adjustment.
    Danno77 and smokinj like this.
  24. Danno77

    Danno77 Minister of Fire

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    I'm kinda at a loss. Could be lots of things that I wouldn't think of right off. Could be the fuel filter, could be the impulse, could be something weird with coil? Might need a carb rebuild for all I know.

    At this point I'd start exploring. I'd pull plug, muffler, intake and look carefully inside. Then i'd check the fuel filter/line, then I'd consider a carb rebuild. It would be awesome if you had a buddy with the same saw. Start swapping known good parts and see what happens! Lol
  25. smokinj

    smokinj Minister of Fire

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    Start with filter its just needs to be done anyway the move to the next step.

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