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Thread: big 2-stroke decompression valve

  1. #1
    Join Date
    Oct 2008
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    Texas
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    Default big 2-stroke decompression valve

    I have a CR480.....for an old bike, I just love the thing. It has a boat-load of torque, a really fun carnival ride.
    I have a routine for starting the thing, but the first time I thought I tore a hole in the bottom of my work boot, I knew I was in for a work out. I bought a pair of Sidi boots to make it painless, but kicking the big beast was still a chore.

    I was across town and stalled the bike one day (tall street gearing...stupid mistake) and I thought it would never refire. That was it, I wasn't putting up w/it any more.

    My CR500 is almost complete....a new top end, so I knew it would be the same issues with that one as well, but on a larger scale. So, the 480 was to be the test vehicle.
    I located a vendor for the self-cancelling (stainless steel) valves, pulled the head, drilled/tapped the hole and screwed the valve in place.

    I can't believe the difference.
    Snap the valve down and kick away.
    Before I'd have to bring it up to TDC and jump on the kicker. Now it's like kicking a strong 125. Cold, hot, or flooded, it doesn't matter. It'll bust off with 3/4/5 kicks every time....I could start it w/tennis shoes (not that I would).

    I was out running a few errands and had to make several stops. It's a pleasure to know it'll start easily every time...instead of the fear of it possibly leaving me stranded.

    I'm a firm believer now in decomp's.
    01 CR500af 83 XL600 hooligans 83 CR480
    97 VFR750 CB1100F 93 Honda Sportster
    74 Suzuki Titan
    75 H1-F 75 RD350
    74 MT250 75 XL350 93 Ducati fighter

  2. #2
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    Sep 2008
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    268

    Default

    Ok i have a kx500 and would love to install one. Were did you get it?

  3. #3
    Join Date
    Oct 2008
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    Texas
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    Default

    I always slow kicked mine, then up to TDC and ard really hard stab on the kicker. It gets tiring after may tries.

    Slow kick now? Nope.
    Snap the valve and start stabbing the kicker....instant happiness.
    01 CR500af 83 XL600 hooligans 83 CR480
    97 VFR750 CB1100F 93 Honda Sportster
    74 Suzuki Titan
    75 H1-F 75 RD350
    74 MT250 75 XL350 93 Ducati fighter

  4. #4
    Join Date
    Mar 2009
    Posts
    13

    Default

    How much does the install cost and is anyone selling just the valve? I found some searchin but there only in packs of 50 of them.

  5. #5
    Join Date
    Oct 2005
    Location
    Roscoe, IL
    Posts
    36

    Default Decompression Valve

    Join and log into http://www.kxriders.com and you can follow the development of a simple, cheap decompression valve system. Lots of KX500 owners on that site, but this modification would work on the CR500 also.

    Last edited by LJW; 10-03-2009 at 03:45 PM. Reason: Added Photo

  6. #6
    Join Date
    Aug 2006
    Location
    Honolulu
    Posts
    538

    Default

    rode a friends cr500 with this valve on it. It literally kicks over easier than my RM250 and my Crf450!
    The streets are dead cuz I fkn killed it.
    2007 & 2009 CRF50F(sold)...2006 CRF450X supermoto - sold... 2005 KLX110 (sold)... 2006 RM250 supermoto (sold) ... 2001 GSXR1000 - blew the motor...2003 GSXR600 in repair for 4 years... 2004 CBR600RR full stunt...KLX110L - my new pride and joy.

  7. #7
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    Oct 2008
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    Pittsburgh, PA
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    Default

    I never had a problem starting my 1990 CR500. As long as you follow the right "routine" it was a 2-3 kick job at most. Also, it was a great deterrent for potential jobbers that wanted to ride it: "If you can start it, you can ride it." Never had anyone that couldn't handle it, ride it.

  8. #8
    Join Date
    Oct 2005
    Location
    Roscoe, IL
    Posts
    36

    Default To Kick or Be Kicked

    Quote Originally Posted by lowercasee View Post
    I never had a problem starting my 1990 CR500. As long as you follow the right "routine" it was a 2-3 kick job at most. Also, it was a great deterrent for potential jobbers that wanted to ride it: "If you can start it, you can ride it." Never had anyone that couldn't handle it, ride it.
    Yah, you're a stud, I'm old and wheezy. After going (losing) a few rounds with a KX500, that little blue button becomes your new best friend.

  9. #9
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    Oct 2008
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    /\ LOL!! Yeah right. I'm as fat and lazy as they come.

  10. #10
    Join Date
    Mar 2007
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    6,273

    Default

    Quote Originally Posted by solidjohnny View Post
    rode a friends cr500 with this valve on it. It literally kicks over easier than my RM250 and my Crf450!
    I could kick it over in slippers seriously, but my bike was tuned properly and would start first kick every time. He'll it started first kick after I built the motor. It was easy as he'll to start without the decomp as well. The best thing about the decomp is that you can start it sitting on the seat. So at long traffic lights I would shut the bike off, set the decomp and get the piston just before tdc and wait.
    2006 husqvarna 530rr. AKA "dirtyfivethirty" or "freight train " Formerly known as Alohar1

    www.FastBikeIndustries.com www.ksrwheels.comwww.balidogrefuge.com

  11. #11
    Join Date
    Jan 2009
    Location
    Michigan
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    Default

    Aren't you suppose to kick a big bore 2T the same as a 4t? Not starting at TDC but pushing slightly past and bringing lever back up and then kicking.

    Makes it much easier to kick my 380 doing that way.
    97 rm250
    01 680r

  12. #12
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    Nov 2007
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    Used to live in Crestview FL, now ????
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    1,718

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    That head on the KX 5 looks like it was made for it!
    ~Tim

    "04 625 SXC
    '04 625 SMC 76,xxx mi.
    '97 CR500 SOLD

  13. #13
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    Mar 2007
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    Default

    Quote Originally Posted by kan3 View Post
    Aren't you suppose to kick a big bore 2T the same as a 4t? Not starting at TDC but pushing slightly past and bringing lever back up and then kicking.

    Makes it much easier to kick my 380 doing that way.
    Correctomundo
    2006 husqvarna 530rr. AKA "dirtyfivethirty" or "freight train " Formerly known as Alohar1

    www.FastBikeIndustries.com www.ksrwheels.comwww.balidogrefuge.com

  14. #14
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    Mar 2007
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    Default

    The best way to start a big bore is.. Turn fuel on. No fuel should be left in the carb the fuel will slowly evaporate and leave just the premix oil. Anyway once the fuel is on for a few sec slow kick threw a few times. Get the piston a c- hair past tdc. Bring the kicker back to the top and kick all the way threw. Having the carb set up properly is key!! Also a good set of reeds and a clean filter. Also when you kick make sure the throttle is open about 1/8. This allows air to get sucked in with the fuel. The throttle being slightly open is very important.
    2006 husqvarna 530rr. AKA "dirtyfivethirty" or "freight train " Formerly known as Alohar1

    www.FastBikeIndustries.com www.ksrwheels.comwww.balidogrefuge.com

  15. #15
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    Sep 2009
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    Shenandoah Valley, VA.
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    Default

    And a big f-'ing leg don't hurt either.....
    WANTED: ONE GOOD WOMAN... Must have motorcycle license, own tools, proficient in bed/kitchen and have thin figure in order to be able to walk between the numerous bikes, quads, trucks, tools and extrenious crap between the garage door and the house.

  16. #16
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    Mar 2007
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    Nah I'm 165 soaking wet. Hell there is a video on YouTube of my wife kicking over my cr500. She is 105 after eating at ruth's Chris. Haha
    2006 husqvarna 530rr. AKA "dirtyfivethirty" or "freight train " Formerly known as Alohar1

    www.FastBikeIndustries.com www.ksrwheels.comwww.balidogrefuge.com

  17. #17
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    Used to live in Crestview FL, now ????
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    Default

    Mine starts 2nd 3rd kick every time using above method. Unless of course she is on the rag. That's only on really hot steamy days or at the start of a recent "dead engine start" race I went to. Lot of fun blowing by all those guys on there 250f woods weapons in the open sections though.

    The little blue knob looks like the $hit but I really don't want to go messing with a good thing though. You know, " If it aint broke, don't fix it".
    ~Tim

    "04 625 SXC
    '04 625 SMC 76,xxx mi.
    '97 CR500 SOLD

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