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372xpw base gasket or no base gasket

Discussion in 'Hot Saws' started by Woodhacker69, Oct 10, 2016.

  1. Woodhacker69

    Woodhacker69 ArboristSite Lurker

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    Hey guys. I'm new to this site as well as chainsaw modding. I am a diesel mechanic by trade however I am trying to learn as much about these cylinder assemblies as I can. I see guys porting and decking their engines. I hear about woods ports etc. Here is the deal. I am on the east coast, and honestly I have yet to find a chainsaw engine fabricator. I do not want to take my cylinder to a hack. I am willing to do the porting by myself but really I don't have knowledge nor know how to perform a task like this properly. I hear about squish on base gaskets etc. I guess what I'm asking is. Is it OK to run the 372xpw without a base gasket and if so what am I gaining? Also how is squish measured? And the last question. Does anyone know a engine guy on the east coast? I am a perfectionist and I want to do something right. Don't get me wrong the 372 has plenty of power for what I use it for. I just am a gear head and love to improve things. I switched to the h/decking filter, high top, I modded the muffler but would love to go to a two stroke expansion pipe. Any ideas on the best pipe? Or do I build one?
     
  2. HuskStihl

    HuskStihl Chairin'em for the sound

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    So, gasket versus gasketless is pretty simple. I'm assuming ur xpw is one of the newer x-tork ones? Generally, huskies aren't all that tight in the squish department from the factory, but you just can't assume it will be ok. Testing the squish is very simple. Fancy way. Take off the cylinder, remove the gasket. Stick some thin solder pieces to the edge of the piston crown with grease at the 12, 3, 6, and 9 o'clock positions, bolt the cylinder on with no gasket, then spin the flywheel thru a revolution, "squishing" the solder. measure with calipers. If all the pieces are thicker than 0.020 inches, get some yamabond 4 as a sealer, put it back together, and run it.
    I will typically just snake some solder thru the plug hole towards the transfer port, and squish it. If it's greater than 0.035, I will delete the gasket, then recheck for safety using the same method without the gasket. You gain some extra torque with this maneuver
     
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  3. weimedog

    weimedog Addicted to ArboristSite

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    What HuskStihl said..with a few embellishments.

    The no base gasket build works on saws with a wide flange to build a good sized ( > .125 ) gasket surface and using Three Bond 1184 it actually acts as an adhesive making an excellent seal. The down side is its almost a metal on metal seal where a standard gasket allows for some expansion / contraction in that joint. Does it matter?? Not really certain as I have yet to have a 1184 gasket fail yet. On builds where its going in to "Pro" service I've done both. On the 562's I also cut a "Pop up" piston along will "decking" the cylinder...since its a high temperature situation in those saws I've moved towards using a gasket, building it to .018 squish along with approx.. .015 popup. Along with a muffler mod its a snappy 562 build! But that's not a 372...different animals.

    You get other things with a simple base gasket delete too and depending on the saw, its either a help; or not. Lowering the cylinder also means you have lowered the ports by the same amount. .020 on those 372's is in the 1 degree range of changing timing. SO you increase the intake duration approx. 2 degrees, delay the exhaust opening by a degree. Both have a minor effect. Also the transfer is moved....with minimal effect. Of the three things, increasing the intake timing can actually help those 372's. Lowering the exhaust & transfers not as much on the 372 although it helps smaller saws like the 350's. SO the net is a base gasket delete gets you more compression and on the positive side, a little more intake duration. Combine that with an intelligent muffler mod and its a noticeable change...more torque.

    IF you have the equipment and skills to deck the cylinder, it opens you up to a whole different level of modifications derived from being able to build pop ups & cutting the actual squish band...another store for another day. That along with some timing changes can radically alter the saw performance.

    BUT to your original question....no base gasket vs. decking the cylinder. It depends. Both work. If you are limited in skills and tool access.. do a base gasket delete. If you have access to equipment that will allow you to deck the cylinder....why stop there??? :)
     
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  4. Woodhacker69

    Woodhacker69 ArboristSite Lurker

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    Hey John no its not an x torque:)
     
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  5. Woodhacker69

    Woodhacker69 ArboristSite Lurker

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    And thank you guys for the replies. I would learn better by seeing it being done. I guess that's where you tube comes in yto play. ;-)
     
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  6. wildman ben

    wildman ben ArboristSite Member

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    so instead of removing the gasket and using three bond, is there any way to just shave down the gasket?
    and ask far as chaging the timing on the intake and exhaust strokes could you just grind the (either top or bottom) of the port so that it gains some of that back to help it more? sounds like it would give advantage to the intake but delay the exhaust, so grinding out the exhaust a bit would help much? and would you grind the top or the bottom to gain that degree back?
     
  7. weimedog

    weimedog Addicted to ArboristSite

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    The amount of theoretical gain isn't worth the pain... :)

    The following video has a discussion on the base gasket delete concept...on a 576xp instead of a 372xp, but the concept is the same. Also the "changes" to compression & timing is about the same.


    How about Pulling a 365 top end and putting on a 372xpw? A little closer to the subject...so it goes through that process....and also a discussion on the 365/372 old style & X-torq series. ALSO if you are just pulling the gasket, you can pull the cylinder with the muffler & carb/intake still attached. Obviously you don't have to pull the piston..:) A little awkward putting it back on but still saves a bunch of time & doesn't disturb as many seals. Last but not least I used "Moto Seal" vs Three Bond. Stick with Three Bond 1184!


    The 365 converted to a 372xpw vs. the 372 X-Torq converted to Huztl 52mm BB top end
     
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  8. weimedog

    weimedog Addicted to ArboristSite

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    How about Stock Jonsered 2172 (Essentially a 372 x-torq) verses "slightly" modded Husqvarna 372xpw to quantify the difference...stock 2172 is bone stock. The 372xpw & Spikes are no base gasket builds...Spike60 also increased the intake timing & cut some at the lower end of the transfers. The 372xpw only has a "No base gasket" build and a Huztl "As Delivered" muffler, runs pretty good doesn't it. With the "new" Husqvarna pricing, this is one of the cheapest and simplest build you can do without effecting reliability even a little bit.

     
  9. weimedog

    weimedog Addicted to ArboristSite

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    Kinda beat that "no base gasket" subject to death.....:) I do both now for my "hobby farm" saws, decking the cylinder with a lathe and USING a gasket, and simply pulling the gasket& using 1184. Depends on the saw & intended use of that saw.
     
  10. weimedog

    weimedog Addicted to ArboristSite

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    Have to write a little addendum because there are a couple of things nagging at me, as I mentioned using Three Bond. What I should mention there are a lot of products out there that have been used.... some should never be in that situation and I'm certain add to the doubters especially if they are in the saw repair business. I ONLY use a Three Bond 1194 or 1184 sealer. Nothing else. I know there are other similar products but this is one of those area's where I use the experience from the past to help decide where to go in the future. I did try A Permatex product.... its been in a saw for two years. I wasn't as comfortable with what I saw when I pulled my test cases apart when evaluating that as an alternative. The seal didn't fail, but it wasn't "stuck" on the case as every three bond sealed saw I've tested to this point has been. In fact sometimes its very hard to pull apart a "Three Bond" saw if its had a chance to really cure. I did a few when testing the concept. SO for me its Three Bond and every time I talk about a no base gasket build, I will be using Three Bond. Period. End of discussion.

    Next. There are some saws I've run into that should never have a "No Base Gasket Build" in my most humble opinion. Husqvarna 562's come to mind. So do saws with a gasket area like a Husqvarna 395. I'm certain there are many more. If a compression gain is to be had for saws with similar issues, in my opinion a lathe or mill to cut the cylinder base is the best way. AND when I assemble both those saw models WITH their stock OEM gaskets, I also glue them on with.....Three Bond 1184.

    Last, when in doubt always use the manufacturer's recommendations guide how you build a saw. That means a gasket. They have engineered that system to survive the design service conditions and service life of that saw. Therefore the most reliable possible solution for repairs will be to OEM specs with OEM parts. I tweak and build saws...but I have piles of saws so it doesn't matter. I've had to go through this in the past and figure this is a good time to go through this again. To tweak a saw the assumption is the person has mechanical back ground and skills...I try to do recipe's where a mechanically inclined person can replicate them without having to buy big dollars machine tools or send things out. But regardless...if a person isn't secure with their mechanical skills and back ground....OEM is the best way to go. Another period and end of story! Don't want to be a wet blanket but the manufacturer's like Husqvarna and Stihl have built a system from the designed product to the servicing of that product hobbyist's like me aren't going to improve on over the long haul...So those who tinker do it knowing there is both risk and the possibility of ruining a perfectly good saw... I've kept an eye on another thread about a completely different saw brand therefore model for a while and there was a realization some folks should stay out of saws...so this is the "knee jerk" reaction I have .. a rant :) So I apologize in advance...
     
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