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Inside the Husqvarna 450 x torq

Discussion in 'Chainsaw' started by Mastermind, Jul 8, 2011.

  1. Mastermind

    Mastermind Work Saw Specialist

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    This is a customers saw, he complained that it has no power and has ran I saw I ported. He wants me to increase the power. I sharpened the chain and increased the cut speed 300%. :laugh:

    I tried to tell him that he just needs to learn to sharpen the chain properly but he still wants it "tuned up". OK, I told him I'll take a look at it.

    I've not been inside a 450 before so I'm learning something here and thought I'd share it with you guys. :cheers:

    The saw is just over a year old. Nice, light 50cc machine.

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    Here's a shot of the chain as delivered. Note the dust. No chips in this baby.

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    I wanted to see how it was cutting for him...

    [video=youtube;uwZOj6Y4SrQ]http://www.youtube.com/watch?v=uwZOj6Y4SrQ[/video]

    This is after I sharpened the chain...

    [video=youtube;jqAXpWewmBY]http://www.youtube.com/watch?v=jqAXpWewmBY[/video]

    I debated just having come to pick up the saw after seeing how bad his sharpening skills were. I really can't see the point of an increase in power in a saw that will be treated this badly. Believe it or not this fellow cuts quite a bit of wood. He has several acres of wooded property and is a damn hard working man. I think I'll take the time to show him how to use a file. I also plan to give him a few extra loops I have laying around. If nothing else maybe I'll end up keeping his chains sharp for him. :)
     
  2. Mastermind

    Mastermind Work Saw Specialist

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    No restrictions in this muffler.

    [​IMG]

    Nice sized exhaust port. Note the transfer tunnels coming from the front of the crankcase.

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    Typical strato setup.

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    Removable transfer covers.

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    I have no plans to change the port timing except for a 5° increase in intake duration. Nothing wild for this little saw.
     
  3. CTYank

    CTYank Peripatetic Sawyer

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    Probably screaming power output has more sex appeal than something tedious like chain maintenance, but it pales in comparison to sharp cutters. Some people may never get it, but it's worth their while to try to educate them. Or maybe you could arrange regular "tune-ups" which are just swaps of chain loops. Lots of luck.

    Working smarter trumps working harder, most times.
     
  4. Mastermind

    Mastermind Work Saw Specialist

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    [​IMG]

    The transfer covers are crudely ground on the end.

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    Cleaning them up also has the effect of widening the port.

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    I used a ball shaped burr to further open the port.

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    I widened the exhaust port 4mm total. This is still only 60% of the bore.

    [​IMG]
     
  5. Mastermind

    Mastermind Work Saw Specialist

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    I've seen a lot of saws fried because of a dull saw and a heavy hand. I really hope I can impress upon this guy how important a sharp chain is.

    I have the saw back together and will post another video in the same wood tomorrow. I hope it gains a little. :)
     
  6. MacLaren

    MacLaren Addicted to ArboristSite

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    Good thread Randy. That was painful watchin the vid of the dull chain. After seeing the after vid with the sharp chain, i think thats a fine little chainsaw. Good work!
     
  7. Terry Syd

    Terry Syd Addicted to ArboristSite

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    Like you said, a lightweight saw - a 10.8 lb powerhead. I've done a fair bit of tuning on my 450 and have documented most of the work in this thread - http://www.arboristsite.com/saw-building-101/107976.htm

    Since the 450 is a bored out 445, the transfer tunnels are sized for a 45cc saw. I found by using some clay and measuring the area of the tunnels that they are 9% too small for the size of the existing transfer port (let alone after I made them wider). Since I increased the area of the transfer ports by 12.5%, in order to get them to flow properly I had to increase the area in the tunnels by 21.5% - that took a lot of work.

    These engines only have 12 degrees of blowdown, so stock they don't cut very fast, but they do have some nice torque for a work saw. If you want to increase the cutting speed, 14 degrees of blowdown will do it.

    A really neat muffler mod is to use the two tubes for the bolts. Just drill in behind the muffler seam to get a hole big enough to put a Dremel bit through. By opening up a hole on the side of the tube opposite the exhaust port, you won't get the sonic wave going directly out of it - it doesn't increase the noise much at all. I brazed up the holes on the outside of the muffler and you can't see them when the muffler is mounted on the saw - a stealth muffler mod.
     
    Last edited: Jul 9, 2011
  8. miking

    miking ArboristSite Operative

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    I owned a 450 for a while myself and thought it was a excellent saw. I sold it in favor of my 530 but the new owner is real happy with it too. Kudos to you for the chain sharpening lesson you'll give him.
     
    REJ2 likes this.
  9. Mastermind

    Mastermind Work Saw Specialist

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    I been running the saw just a little and have to say I like it well enough. With some time spent in the lower transfer tunnels and the entrance it would most likely come alive. I just opened it up a tad and feel like it responded well. The muffler still exits through the stock outlet with screen. I did open the hole under the screen up quite a bit. In this video I really put some pressure on it in the first two cuts, it pulled down some but not nearly as much as it did before, you could bog it out easily in stock form. The next three cuts I just let it eat. It's a nice running saw but I still ain't sold on the strato. :D

    [video=youtube;jiXwRVDy8lE]http://www.youtube.com/watch?v=jiXwRVDy8lE[/video]
     
  10. SawTroll

    SawTroll Information Collector

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    Well, it isn't a pro saw, and the power surely is much lower than the 346xp, while the weight barely is lower....;)
     
  11. Terry Syd

    Terry Syd Addicted to ArboristSite

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    Randy, the 450 is my first chainsaw. I've got a fair bit of experience tuning engines, but had no experience in regards to the particulars of a chainsaw powerband. Throw in my first exposure to a 'strato' and it was a learning experience. You can see how from the posts in that thread I linked to that I was trying to sort out what works and what doesn't.

    The saw is a ripper now, but it took a lot of work. It will pull an 8 pin with the 18" bar. I'm waiting for my 20" chains to stretch a bit to see if I can run the 8 pin on the 20". The 445/450 has a 13,000 limiter on the coil. As long as I keep my chains sharp it isn't a problem. However, if the chain gets dull, the engine will start bouncing off the limiter in the cut.

    The strato engine is IMO a superior engine. The time/area on the intake cycle is far greater than a conventional two-stroke. The 450 has an intake opening that is 95% of bore width. Some of the other stratos exceed 100%.

    When you have that much time/area for the intake cycle, you don't need a lot of intake timing - but you do need to allow the engine to breath. The stock carb has an 11mm venturi, I put a 13.5mm venturi carb off a 570 on mine. I ended up with a combined area of the carb and strato intake equivalent to a 19mm venturi carb.

    The stock intake timing is 144 degrees with a strato timing of 154 degrees. You will see from that thread that I found matching the intake timing to the strato timing gave me the best power. Matching the timing allows the most flow while retaining the most base compression. Essentially, on my modded saw I am running the stock 'intake' timing of 154 degrees. Whereas many porters use an intake timing of 160 degrees or more, I can retain the torque of the shorter intake cycle and still have the engine breath at the higher revs using the greater time/area of the intake and the bigger carb.

    You may have left some on the table with the intake system. The strato ports get partially blocked by the shape of the piston at TDC. You can trim the piston cutaway so that the strato ports are fully open at TDC. You might also want to match the intake and strato timing. That is easy enough with the transfer port covers off as you can watch when the strato cutaway peeks over the bottom of the transfer port and then look into the intake port to see if the intake port is opening at the same time.

    My saw puts out enough power that I had to block off the 'air injection' system in order to keep it alive. The air injection system takes air off the fly wheel, what was happening on my saw was the more I got the engine to breath, the less air was available for cooling. I was producing more heat and at the same time removing air over the fins.

    If it was your own saw, then you might be able to justify doing all the transfer tunnel work, but not for a customer. It was a fun project for me, but then I'm a compulsive tuner.
     
  12. Mastermind

    Mastermind Work Saw Specialist

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    No it's far from a pro saw Niko. :laugh:

    On the bright side though, is has less emissions than a fart. :D
     
  13. Mastermind

    Mastermind Work Saw Specialist

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    Yes Terry, that is the rub here. I would go back inside several times on my own saw. I too am compulsive. :)

    I read the linked thread twice, and can say that you surely learned a lot about the stratified design, and taught me some as well.

    In my opinion this is a fine saw for the casual user even in stock form. This is a 350.00 saw, far from the price of a pro model. Now to teach the old boy to keep it sharp. :dizzy:
     
  14. SawTroll

    SawTroll Information Collector

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    Yup - I believe it is very good for a "homeowner" design! :D
     
  15. Terry Syd

    Terry Syd Addicted to ArboristSite

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    I noticed he was using the H30/95VP chain. Get him one of those Husky roller guides for that chain and he should be right - provided he uses it.
     
  16. Mastermind

    Mastermind Work Saw Specialist

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    I thought about sticking a full chisel on it but was afraid it would dull faster, which would mean even more "sharpening" for him. :laugh:
     
  17. SawTroll

    SawTroll Information Collector

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    That should be pretty good on that saw, but I would want to try 20LP(X) on the original bar as well......
     
  18. zogger

    zogger Tree Freak

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    wait

    That dude is *never* going to sharpen his chain, or he would be doing it already. Most likely he tried and can't sharpen, some people just don't have fine motor skills, they jiggle too much (you see this trying to show people how to shoot..some people will never be able to be accurate..the medcos call this "purpose tremors" and if they get them or have them, retire or never do surgery) . Some people, guys, are just great on heavy duty strength/work skills, but just can't cut it-pun intended-on the more delicate tasks that take a little finesse. And sharpening is finesse.. Just is, folks are different....

    But...there is a very practical solution to get him happy and back cutting, with a sharp chain he can keep sharp. He is a prime candidate for that new oregon powersharp whatever the heck it is called system. Sounds perfect for him. Sell him on one of those. (if they have a model/bar and chain for that saw, that is)
     
  19. Mastermind

    Mastermind Work Saw Specialist

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    I'll be damned if that ain't a fine idea. I saw one of those and the old barracuda system timed and tested at the winter GTG (thanks to Terry Landrum!!!) and they worked very well. They cut pretty damn fast too. I'll keep that in mind! Thanks.
     
  20. Terry Syd

    Terry Syd Addicted to ArboristSite

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    Randy, as a fellow sufferer of 'Tim Allen Disease', you may want to subscribe to that strato thread. I've been doing some research and experimenting on Pop Off Pressures (POP) on diaphragm carbs. Here's a link for a thread in 2008 - http://www.arboristsite.com/arborist-101/67662.htm

    I'm trying to develop some practical theories on tuning the POPs on these saw carbs. There is some information on the kart and aero forums, but not much on troubleshooting to get better performance. Since my saw has a broad powerband, I'm trying to get a better metering of fuel over that broad range. I've had some success so far, so I think I'm on the right track.

    I'll post the results of my experiments in that strato thread.
     

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