OzVMX Forum
Clubroom => Tech Talk => Topic started by: Kane Mcguire on October 08, 2011, 08:04:43 pm
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i want to fit a decompression valve to a big bore husky. where can they be bought? thanks.
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Here you go 14mm longreach for the Husky
http://vulcanworks.net/Compression-Releases-orderby0-p-1-c-1.html
Cheers
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thanks heaps!
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try Les at mainly maico
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I've seen them being sold regularly on ebay somewhere for a lot less than those Harley ones.
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got a few at home.
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Vulcan highly recommended but a little pricey I agree. I couldn't find any others on eBay that were 14mm with a long enough reach to stick out through the fins on the head. Not worth using cheap shit.
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I've used those Vulcan decompressors on my bikes for a few years and I swear by them. The only bike I can't use one on is the 360 RT1 motor in my Cheney because the exhaust goes right accross the 'spare' plug hole. These gizmo's are shitloads better than the OEM Yamaha and Maico items.
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I have used one sucessfully on a CR 500 from a VICTA lawn mower.About $30 bucks from a mower shop
" zip on the do da your up and away"!
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Are these(vulcans) difficult to fit to bikes that dont have spare plug hole's - eg 83' huskies where there's not a lot of room from pipe etc -anybody done it ?
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Shoey's Husky 430 and 500 head mods for decomp ;)
(http://i781.photobucket.com/albums/yy94/HuskyRacer/03132010116.jpg)
(http://i781.photobucket.com/albums/yy94/HuskyRacer/CD72010QLD203.jpg)
(http://i781.photobucket.com/albums/yy94/HuskyRacer/03042010098.jpg)
(http://i781.photobucket.com/albums/yy94/HuskyRacer/03042010097.jpg)
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Great shot's 67 thanks for that ! looks fairly straight forward, damn nice 430 that one :)
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(http://i1113.photobucket.com/albums/k501/KTMaico/P1050953.jpg)
(http://i1113.photobucket.com/albums/k501/KTMaico/P1050954.jpg)
Used on my Maico 490, good product pity the guy at Vulcan Works I talked to was a complete dipstick. I have a couple spare.
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Just bought a couple of the short ones and am going to try to fit one to a Wr400/85 head.
Watercooled so should be fun.
I have a genetic back problem and can't get enough movement/power in my leg to kick the old girl over + the compression on mine is a lot higher than the original 12/1 ;D
Will post pikkys if it works out.
If it don't then lesson learnt. ;D
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For what it's worth, if I had to put in a decompression valve on any big bore bike I would not waste the time and money using 13mm ones (standard spark plug size). I will be changing my Maico 490 over to a 18mm one as soon as I can. The standard size units still don't give my bike enough compression release to make starting that easy. To start any bike bore bike they need a decent kick to get the fastest rotation of the motor as possible, (fuel suction, voltage/spark generation) and a 18mm decomp valve should give you maximum pressure release in your combustion chamber. I believe that the UK Maico owners tend to use the 18mm units over the standard.
Want any Vulcan Work Auto Decompression valves give me a call.
Kevin
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(http://i753.photobucket.com/albums/xx172/mike52_photo/WR400/85007.jpg)
(http://i753.photobucket.com/albums/xx172/mike52_photo/WR400/85009.jpg)
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(http://i753.photobucket.com/albums/xx172/mike52_photo/WR400/85007.jpg)
Finally fired the 400 up yesterday and I am very happy with the 10mm decomp valve.
The bike kicked back once and I can still walk.
Can,t ask for more than that.
Easy to start too. :)
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Sent my head to the states and had this done for $125 now the CR500 kicks like a MR50 :) (almost) :D
Top job and it looks factoryish too.
(http://i115.photobucket.com/albums/n309/gtr_05/seawolf0005-1.jpg) (http://s115.photobucket.com/user/gtr_05/media/seawolf0005-1.jpg.html)
(http://i115.photobucket.com/albums/n309/gtr_05/seawolf0007-1.jpg) (http://s115.photobucket.com/user/gtr_05/media/seawolf0007-1.jpg.html)
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the decompressor from the stilh 100cc farmboss chain saw might be worth ago too,there from memory 10mm thread size.the victa decomp valves come in 2 types,the long one from older split c/case moors and the short one from power torque motors.they need crank case vacuum to pull in ;)
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Can we get small decomp valves,m10 or 12, with provision for cable operation?
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Lots of m10 on eBay. Why do you need cable operation though? Quite easy to lean down and push the poppet valve in to open it if you can get one that protrudes past the fins on the engine. It it doesn't start on first kick you need to do it each time you kick. If fins too long then it will be a mongrel unless you machine some room to access the decomp device with your finger of else use a stick to push it in ;D ;D
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Cable because, it rarely starts 1st kick and I can catch a stall while still rolling. XC500
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My AE500 doesn't start first kick normally and I don't find it a hassle not using a cable operated device. It being an auto doesn't stall very often so I can't comment on the usefulness of having a cable operated setup ;D Good luck with the search.
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Changed mine to that sideways style as they are easier to reach with the long side tank.
(http://i753.photobucket.com/albums/xx172/mike52_photo/decomps/400and240001.jpg) (http://s753.photobucket.com/user/mike52_photo/media/decomps/400and240001.jpg.html)
The cable operated ones can give you a problem if you use them as an engine brake as they can suck in dust on the down stroke.
The one Mr500 has pictured is used on the Husqvarna Quickcut saw so that may be a place to start looking.
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I've been thinking about a decomp valve for my it490. Can anyone recommend a machine shop in Melbourne for the head work?
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Got me scratching my [bald spot], thought any decomp in the head was to 'stop the motor' or get a rolling re-start downhill or [like a trials bike of old] stop it locking the wheel & stalling & use it as engine braking. These type you guy have must let a minute amount out if they run like that? or do they automatically shut off after one puff. Was thinking the best way to go [albeit difficult if no place provided] is like the old 360 Yams where it's letting compression off from a point taken half way between top of ex/port & top of cylinder, cable operated & will run all day like that if you want--makes a soft motor for creeping around difficult situations, then close the lever &--full power. The old orange AG175's had this hole open all the time for easy starting [bleeds off into exhaust port], & so did RD400's. Of course us young fellas blocked everything off because, well, we were loosing horses!!,[actually i wasn't young even then--depressing that] but did work & worked well. Talking 490's I think someone asked [IT490--or YZ], i did exactly that [open all the time] to my YZ465G, went enduro riding & was just too bloody hard to kick over when your panting out of breath stuck in a Fkn mud hole thinking--never again--till next time!!. Was a bit of a gamble drilling it. Was long long ago but by memory i made a slight grind mark in the cylinder liner where i wanted it to exit the liner then started drilling steeply down till it came out in the exhaust port, hoping like hell it wouldn't appear through the fins before it got there & luckily it didn't. Can't recall the drill size but think it was 6mm, maybe 5 or 5.5mm. Plan was that if i didn't like it i could just tap a thread & bung it from probably the outlet into the port end [if i could have got straight on to it to thread etc]. Ended up selling it like that, with lights on etc as was then awaiting the YZ490J. Often wondered if the new owner ever thought it sounded a bit chuffy at idle, probably did knock the overall performance a bit & the ideal set up would be one [like the old RT1/2/3 & later 360A/B plus i think SC500--operated by the kick start automatically via a cable], but no room to do that as not cast with enough meet where you'd want to fit it [i think]. Anyway, forgot where i was going with this--probably nowhere. Carry on. Cheers.
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Yes they close after the first puff. They are designed to be used on the big American V Twins to take load off the starter motor. Designed to screw into a second spark plug hole. Your requirement to use as a motor compression release while the engine is operating is not suited to these devices.
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is that a harley accesorie won?
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Here's a Harley accessory decompressor on my 360 Yam motor.
(http://i1112.photobucket.com/albums/k495/firko2/flattracker008_zpsf1322e4b.jpg) (http://s1112.photobucket.com/user/firko2/media/flattracker008_zpsf1322e4b.jpg.html)
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I've just put one from a Husqvarna chain saw on my Triumph 650 Twingle, has a 10mm thread and works a treat, starts easily with no more bent kick starter levers!!!!
Mike
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The one shown on my Husky is a Harley aftermarket part.
Over the hill , Push these and they stay open until the engine fires then they slam shut and stay shut until you push them again.
Nothing like the old cable types.
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Thanks for that [Mike52 & others], i'm learning all the time. Triumph 650 twingle's got me thinking, she'd be a beastie to kick over alright. Did an RD350 as a 'twingle' years ago [with dirt in mind] but sold it before i got it running damn it, was close too running too, just too tight to spend money on new piston kits at the time. Your type of de-comp in the head would have been ideal. Thanks.
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Got 4 x 246cc four stroke pots at 12.4/1 comp all in a line, stuff decompresses. I just refitted the electric starter motor with a couple of extra electrical relays :D
Sorry ::) Seriously, Have fitted "Vulcan" brand decomps over the years ,never had any complaints, worth the dollars.
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I got some on cable and bar levers if any one wants to buy some
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On Oz Ebay http://www.ebay.com.au/itm/cr500-cr480-cylinder-head-decompression-modification-cool-head-rm465-/121126959361?pt=AU_Motorcycles&hash=item1c33bab901&_uhb=1
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Hello, Just wanted to revive an old thread, does anyone know where to purchase the compression valve from these days?
Looking to fit it to a 87 Cr500, there seems to be a lot on Ebay but just wanted to purchase something that is a proven product and the correct size?
Thanks.
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https://secure.vulcanworks.net/store/Compression-Release-Set-14mm-Long-Reach.html
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https://secure.vulcanworks.net/store/Compression-Release-Set-14mm-Long-Reach.html
I've fitted a few and have used chainsaw units- Stihl/Husky push button type with the 10 x 1.0 thread; $150 US sounds a bit exxy. Stihl genuine are about $20 or you can get a 3 for $12 with free postage Chinese deal from Ebay.
Getting the unit is easy, the install in a water cooled bike needs a bit of thought. Most I've seen involve a welded boss that the decomp screws into. I make an adaptor using a M6 thread that requires only drilling and tapping and can go through the water jacket.
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Thanks for your help people, much appreciated.