Auto Decompression Conversion for 2 stroke Husky - easy

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Hi, thought I would post the Automatic decompression setup I installed on my 85 WR430, because I am old and lazy I was starting to avoid riding my Husky because of the "huge" compression when trying to restart it after a fall or stalling....its usually when your totally shagged and you cant even lift the ole left leg up high enough to kick it!!, so to the purist out there please forgive me for this but I now get on the bike every weekend hassle free and its easy to start in any situation even when its flooded!!! makes it a lot more fun to ride.......

I had a spare 430 head and welded in the fitting for a decompression valve which is commonly used on 2 stroke motors, it has a small valve shaped much like a 4 stoke valve and seat built into the bottom unit and is fail safe (about $20 at a mower shop), funnily this is the same part Husqvarna have as a accessory on thier 2010 360 Husky 2T bigbore decomp head upgrades - second to last photo ( cost $525). I fitted a threaded tail into the reed block for the vacumn line,as soon as the bike fires it closes the small valve and runs as per normal. Maybe a little more difficult for Aircooled but can be done.

cost me around $100 bucks NZ all up......and can be changed back to normal head and compression at anytime or just block the holes.
Phil

Thanks for sharing! I've often wondered how these worked.

nice looking bike!

Thanks....it has a home made Glass tank, i have all the original white bits for Vinduro, but i love this "hot rod" MX look

cheers
Phil

tank query

Interesting! some info on making the tank would be good! I will ask some questions!

1.Did you you make a plug and mold or a mold off existing tank?

2. I am guessing you have a machined aluminium male thread spigot set in the glass for the fuel cap to bite onto?

3.Did you use vinyl ester resin?

4. What paint did you use on it?

Hello NZ
HOW DOES IT WORKS THIS DECOMPRESSOR ???
Thanks
Michel

The Fibreglass Tank - when i say "homemade' a good mate who is a bit of a glass and carbon fibre guru ( see the radiator scoops...carbon fibre) made it from taking a mould off the bottom of the original tank for frame shape and mounting holes, he then used polystyrene to get the shape we were happy with and close to the older Husky tanks, he poured acetone in to melt the polystyrene out and married them together and used as a mould and yes a aluminum spiggot wass moulded in for the cap....the tank is very strong and light. Dont know about the resins but will ask him, the paint is a 2 pak with extra hardners and many coats including clears, it doesnt scratch easy and polishes up good, this is probably 2 years old now?

The Decompressor - It works by the spring loaded valve in the bottom of the unit ( looks like a small 4 stroke valve) being partialy open to allow some compression past and pass through small vent holes with a filter under the base of mushroom shaped unit, once the bike fires ( which is quick and easy)and develops a vacumn from the inlet manifold sucking fuel into the combustion chamber it holds the valve shut and the bike runs as normal. These are a serviceable unit if the filter gets dirty ( very rare as it blows out not sucks in). Dare i say it but these are exactly the same as they fit onto a 2T Victa type lawn mower or similar....dont tell too many people that lol, google victa decompression valve...
I always used to boast about the amount of compression in original form and is easy to change back but as i got a little older it was getting harder for me...

In NZ we dont have a lot of access to Husky bits so we have to use a bit of Kiwi Ingenuity

Cheers
Phil

exactly......kicks like a 125 but still has the same arm stretching power!!

A guy a few hours away has just done this setup on his CR500, he reckons its like a new lease on life for him also as he has had major hip surgery....and is 52,good on him

Phil

This is the setup i put on my 81 430 CR

I will be happy if it kicks like a 250

Very nice. That valve is a great way of doing this. May just have to follow suit as well. Thanks for sharing....

nice job, have a couple of mates using similar setup

True or not I have heard that the factory stopped using compression release devices due to dirt getting into the engine. Perhaps what you did in the reed block cures this. There are other ways to approach the issue if you are only concerned about starting and not using it as some sort of brake. A) create a small hole from inside the exhaust passage to about half up the bore above the exhaust port. I have a 420 cylinder with this feature and it is used by brand x. B) Use a 500 head on the 430. don't knock it until you try it. If your problem is stalling and then falling not in the order you post you could be quite pleased.

Hey NZ,

How has this setup worked out for your mates?

Is it reliable?

Does it kick as easy as your setup?

HighDez,
What angle did you have machined in the squish area of your cylinder head?

Highdez..... yeah fine. they do watch the dirt and water blasting around the valve tho, at least 3 years old now no issues

2 degrees
I also machined the diameter to match the bore I.D.

NZ,
Are your mates using the TP engineering valve?

Thanks, thats what I was told 1.5-2deg. My 500's have "0" and show detonation damage on both pistons in that area.