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Clamshell sealing (345)

Discussion in 'Chainsaw' started by 9050lx, Nov 13, 2019.

  1. 9050lx

    9050lx ArboristSite Operative

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    Husqvarna 345 torn back down after piston replacement. Looks like an air leak around the top of the bearings or maybe the plastic flange as it looks like a miniscule amount of sealer was left. Failed a vacuum test. I used 3bond 1211 and let it dry 3 days before attempting to run, and at first it ran well. Wondering if I should attempt the 3bond again, or maybe Dirko as I have both of these at hand. How long should I let the sealer setup before pressing parts together?Any reasonable reply is appreciated.
     
  2. irhunter

    irhunter ArboristSite Operative

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  3. Duce

    Duce Addicted to ArboristSite

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    Motoseal is assemble and allow to set 24 hours.
     
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  4. lostone

    lostone Stihl Runnin

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    I haven't had a chance to use it yet but I bought Hylomar Blue, There are different grades of it but if it's good enough for Royle Royce to use in their jet engines then I figure it's safe for me to try on a chainsaw.

    Hylomar Blue, but if I read it correctly the M is even better but don't take my word for it and take the time to read up on it.

    Hylomar M

    There is Hylomar Aerograde as well (a bit overkill).
     
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  5. SEAM

    SEAM Addicted to ArboristSite

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    I've wrestled with a 345 before. Ran fine for a few minutes after replacing the seals and bearings, and then developed the leak symptoms again - repeatedly. My solution: I don't touch that design any more.
    I think the problem is the plastic housing that also serves as the lower crankcase half. Plastic will warp when it gets too warm/hot and generally does not follow the expansion pattern of metals exposed to heat. Metal on plastic for a crankcase is just a poor choice in my opinion, and a single overheating of the engine (seizure or bearing failure) may make the case unusable for a rebuild.
    The Stihl version features a true clamshell design and the crank rotates in a full enclosure which is easier to seal - not perfect but way better in my opinion. Never had any problems with the Stihl version of clamshells.

    Good luck! Let us know if and how the problem got solved. ;)
     
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  6. irhunter

    irhunter ArboristSite Operative

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    It is not just a Stihl design. Some, if not all, older Husky clamshells had the lower half of the clamshell made of aluminum (or, some such metal). At least my 36 and 136 did,

    Roy Whole clamshell.jpg
     
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  7. SEAM

    SEAM Addicted to ArboristSite

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    You're right, I forgot about the early models... those were real clamshells. ;)
     
  8. irhunter

    irhunter ArboristSite Operative

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    I wonder if any of the newer Stihls use the no-bottom-metal design.

    My understanding is that saws like the Husky 350 had the bearings fully supported by plastic (top and bottom); with a pro-like cylinder. But, I have not had one apart, and do not know for sure.
     
  9. Huskitoter

    Huskitoter ArboristSite Operative

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    The 350 case is identical to the 340 and 345. The 350 riser (bearing cup) is metal and has the same shape as the bottom of a 345 cyl. It's what enables the use of non-clam cylinders.

    It might not be a bad idea to place a sheet of fine sand paper on a flat surface and run the base of the cylinder over it to make sure it hasn't warped any.
     
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  10. 9050lx

    9050lx ArboristSite Operative

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    Yeah, this 345 just may be a candidate for a 346 OEM cylinder and piston.Anyone know what length and diameter cap screws are needed for a HL supply aftermarket bearing cap?I reassembled with Dirko, started right up of course, and held vacuum after reassembly.I just don't trust it.Also, does spike60 still sell 346 cylinder kits?
     
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  11. svk

    svk A little bit of everything

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    You can check with bob but I think I remember him saying he doesn’t ship parts anymore, only pro saws.

    Not sure on the length of screws but the OE ones for a 350 will work.
     
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  12. irhunter

    irhunter ArboristSite Operative

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    If you can't get the 345 cylinder to seal to the plastic, will sealing the 346 cap to the 345 plastic be more certain?
     
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  13. 9050lx

    9050lx ArboristSite Operative

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    Not Certain, But it looks like a more positive seal can be achieved with two separate points of assembly.Plus, its a great excuse to build a 346 clone.I can also decree the 346 top end as a christmas present.
     
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  14. Huskitoter

    Huskitoter ArboristSite Operative

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    That's a nice gift to buy yourself. Better than a model car by a long shot.
     
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  15. 9050lx

    9050lx ArboristSite Operative

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    also keeps me out from underneath the fox body in the cold weather.Well it really isn't cold here yet.
     
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  16. 9050lx

    9050lx ArboristSite Operative

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    Today I bought some 5 mm dia. x 16mm long cap screws for the cylinder mount side of the Farmertec Husqvarna 350-style bearing cup. The bottom side was I believe 6mm x 16 mm but I havent actually bought the bottom length ones yet. Ace hardware.
     
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  17. 9050lx

    9050lx ArboristSite Operative

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    Well, heck with it.Bought an OEM 346 cylinder kit.Probably go on my 353 and put the 353 cylinder and a bearing cap on the 345.All the best stuff will go on the 353.
     
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