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Ported saw am I running wrong fuel mixture

Discussion in 'Chainsaw' started by Jared31, Dec 4, 2019.

  1. Jared31

    Jared31 ArboristSite Operative

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    So I recently bought a brand new stihl ms261 cm and had it ported by a reputable porter on this site. The saw runs awesome with tons of power and torque but I think I’m running to rich. I’ve run about 5 tanks through it and I’m still getting black oil out the exhaust. I’m running 90 octane ethanol free with yamalube r2 at 32:1 ratio. Is that to rich should I be looking at maybe switching to 40:1. I just ordered a quart of motul 800 2t off road 2 cycle oil. I was going to mix up a batch with that but wanted your guys input to what ratio
     
  2. DND 9000

    DND 9000 ArboristSite Guru

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    The oil that comes out of the exhaust is because the piston rings are not fully seated. (New saw.) Run it severall more tanks and don`t think about it and you will see there will be no more oil coming out when the saw is fully broken in. That`s normal. I`ve seen it on saws and clearing saws.
     
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  3. Jared31

    Jared31 ArboristSite Operative

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    Awesome thankyou. Should I keep the 32:1 mix
     
  4. DND 9000

    DND 9000 ArboristSite Guru

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    When the saw is running good with the 32:1 mix, keep it. Some guys say that the m-tronic likes better 40:1, but I think you should see what works best for you. It also depends on the oil being used.
     
  5. Andyshine77

    Andyshine77 Tree Freak

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    Running rich refers to the air fuel mixture, not how much oil is in the fuel. A heavy oil to fuel ratio is a separate thing.

    Anyway a few things could be going on. 2R has a low flash point so you shouldn't be seeing all that much residual oil. If you're not loading the saw much making a lot of small quick cuts, it may in fact be running a bit fuel rich, as your no putting enough load on the, this causes incomplete combination.

    The Mtronic system may not be adjusting correctly. Does the saw sound rich when running in the cut, 4 stroking badly?

    With nodded mufflers they often don't get hot enough to burn off any excess oil if the saws not run under good load. So you can get a bit of oil out the exhaust, you will always have some oil residue, that's the nature of two cycle engines.

    You could in fact be using too much oil for how you're using the saw, running 40:1 is perfectly fine in a ported work saw.

    If you have this problem with 2R it will be much worse with Motul 800. 800 offers extreme protection, but is too much for the average saw in most normal applications and will not burn completely.
     
  6. Andyshine77

    Andyshine77 Tree Freak

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    The rings not being seated has absolutely nothing to do with it.
     
  7. Jared31

    Jared31 ArboristSite Operative

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    All good information. I’ll try 40:1 and see what happens
     
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  8. drf255

    drf255 BAD CAD

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    I’d agree with the above. I use Motul800 and it doesn’t burn unless subjected to extreme heat (ie Milling). It will create a lot of residue, but keeps things nice and lubed.

    I’ve personally had issues with MT saw and 32:1 which was felt to be secondary to the Motul800. H1R and Motul800 are both very viscous and create a thicker mix that the MT can’t flow enough of. The problem seems to be accentuated in the smaller saws with smaller carb jets. But this would cause a lean and not rich condition.

    Personally think you are overthinking it. Wipe the extra oil off and keep cutting. If the saw is running well, the extra oil is a good thing.
     
  9. huskihl

    huskihl Addicted to ArboristSite

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    I ported this saw. It was the first 261 I did since you and I had the lean running issue. I drilled the main nozzle from .6 to .7mm in an attempt to allow more fuel. It definitely made a difference. 10 successive cuts with an 18” bar buried and it showed zero symptoms of our previous problems.

    I’m not certain if it’s Jared’s cutting style, the added oil, brand of oil, or perhaps I should’ve drilled to only .65mm. I figured the mtronic would have more control than that and still be able to adjust accordingly.

    @Jared31
    Try a .325x8 sprocket. That might be just the ticket to put more load on the saw and dry it up
     
  10. holeycow

    holeycow Addicted to ArboristSite

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    That yamalube and that motul are both very "spoogy" imo.

    try motul 710
     
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  11. cuinrearview

    cuinrearview Red saw lover

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    My ported 365 with XT carb pops a little and won't rev out all the way. You think it's the coil?
     
  12. huskihl

    huskihl Addicted to ArboristSite

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    Hard to say. It could be tuned too rich or it could have too much timing advance also
     
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  13. andy at clover

    andy at clover Woods!

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    Nothing technical ahead here.....

    I use Yamalube R2 at 32:1 in My Milling saw and can share what I've found.
    For the MMWS3120 milling, that saw runs great on that 32:1 mix for long cuts... sometimes holding the trigger for a full tank in a go ripping with that big saw!
    On the other hand, The stock ms241 and Ported MS441 don't run as good although they run good enough on that mix.
    Throttle response seems poor(er) so..I try and avoid using the stronger mix in those saws.
    Felling and big bucks with 441 and limbing and smaller bucking with 241.
    I think the use matters. Big Bucking the M-tronic can catch up and adjust (or it just seems more forgiving than limbing).
    Limbing and short burst with the 241 the stronger mix just makes the saw seem a bit slower.. maybe it's operator perception.

    I suppose it makes sense .....The M-Tronic is designed/calibrated for 50:1 mix........ I now use 40:1
    Maybe 40:1 is close enough to not notice much change but once you start getting stronger, it seems like it gets out of whack!

    just my 2c
     
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  14. president

    president Addicted to ArboristSite

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    Thanks!
     
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  15. Chris-PA

    Chris-PA Where the Wild Things Are

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    Yup, if the rings don't seat you'll get crankcase oil blowing by into the cylinder....:innocent:
     
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  16. MaddBomber

    MaddBomber ArboristSite Operative

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    Completely agree. 40:1 is as strong as I'd go for a general use saw (50-70cc). The MTron & ATune systems measure volume. More oil=less gas per "gulp"(pulse). Gas=power. A lot of reputable guys that port recommend 40:1. A lot of motocross racers (back in the two stroke days) would tune thier mix ratio to different track conditions.... As well as their jet sizes, which obviously makes way more of a difference.
    The key is to have only as much oil as is needed to ensure thorough lubrication, any more and you're invariably going to lose power.
    Size of the rotating assembly is also a huge factor... Bigger bearings require more oil.
    IMO
     
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  17. blsnelling

    blsnelling Site Contributor

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    What was the deal that the jet needed drilled?
     
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  18. panolo

    panolo Seldom right...Always opinionated!

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    I don't use 2R. We had some of the same issues in race bikes with guys that were putters same with banshees and blasters. It's great oil but likes to get hot to burn. I've always ran 2M and have had zero issues. Couldn't tell you the flash point differences but rarely did you see a good running outboard have excess unburnt coming from the exhaust. And many outboards around here do lots of idling and there are not a ton of long runs.
     
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  19. huskihl

    huskihl Addicted to ArboristSite

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    Once ported, 7 consecutive cuts in an 18” log would overheat the saw and the mtron would prevent it from revving for a few seconds until it cooled down.
     
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