• Husqvarna Motorcycles Made In Sweden - About 1988 and older

  • Hi everyone,

    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

    When he passed, I worked with his kids to gather the necessary credentials to keep this site running. Since then (and for however long they worked with Coffee), Woodschick and Dirtdame have been maintaining the site and covering the costs. Without their hard work and financial support, CafeHusky would have been lost.

    Over the past couple of weeks, I’ve been working to migrate the site to a free cloud compute instance so that Woodschick and Dirtdame no longer have to fund it. At the same time, I’ve updated the site to a current version of XenForo (the discussion software it runs on). The previous version was outdated and no longer supported.

    Unfortunately, the new software version doesn’t support importing the old site’s styles, so for now, you’ll see the XenForo default style. This may change over time.

    Coffee didn’t document the work he did on the site, so I’ve been digging through the old setup to understand how everything was running. There may still be things I’ve missed. One known issue is that email functionality is not yet working on the new site, but I hope to resolve this over time.

    Thanks for your patience and support!

Compression release?

I haven't seen the chain saw decompression so can't comment on those . With the hole from the exhaust port thru to the cylinder to me seems that the lower the rpm , the greater effect that it would have to bleed off compression . Seems to me that 2 things would have to be considered , location of hole and size .
Location of hole , the closer to the top of the cylinder the more distance the piston can travel upwards bleeding compression . When the piston passes the top of the hole it's like when the piston passes one of the ports , closing it even though the compression release is still open leaving the remaining upward travel to boulder compression for starting . Now if the hole is lower , there is less upward piston travel to decompression off and should have a higher compression than the higher placed hole for starting . This is assuming identical size holes .
Now as for size of the hole , like a carburetor , the bigger the hole the more it can flow than a smaller hole given the same location . So what I mention before about Maico owners going to the 18 mm compression release , they are refilling and tapping the existing 14 mms hole bigger to fit the 18 mms comp release . The 18 mms release itself allows more pressure to be released but since the hole in the cylinder is also now 2 mms higher , the piston will pass the hole later on the upward travel allowing even more compression to be bled off.
As for snagging a ring , after drilling , champer the hole .
That 14 or 18 mms hole should be smaller than the other ports plus no other holes at that height .
Are the chain saw decompression 1 way or do they also allow air in ?
 
Fluff Brown the long time owner of AJS after Norton Villiers went bust showed me a 410 barrel/jug where he had done this to ease starting.
 
Put mine in the head 10mm straight through but used a decomp valve with a metal plunger button and welded it to the top so the plunger cannot break out of the body and into the engine.
The plunger sits flush with the dome surface, heated the head up before tapping the thread, the button sits lower than the ac fins but is operated by a modified choke lever attached to the head as operating it without would lead to burnt gloves.
 
420s don't need compression releases lol well ours doesn't
All the shops offering decomp services will have a small hole through from the decomp . Google images it .
 
I was going to install a compression release on the rear of the ac cylinder about 1" down but the ring gap is on the rear of the piston right where the hole for the cr would be. Going to off set the cr so it doesn't interfere with the ring gap.

I was part of a test which involved the Husqvarna 2100 chainsaws with a newly designed cylinder and piston porting. The engineers at Husqvarna put the arrows that point forward on the piston for installation were backwards. We noticed it during assembly. A call to Husqvarna they said to install it that way. The ring gap passed through a port in the cylinder. We didn't listen and installed it the correct way. I tested it in the field. We had the only saw that didn't fail in the test. The new design was better on fuel consumption and had a tad more torqu and speed.
 
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