decompression valve. where from?

[Mike52]

[Mike52]

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.

[mr500]

Sent my head to the states and had this done for $125 now the CR500 kicks like a MR50 (almost)
Top job and it looks factoryish too.

[TT5 Matt]

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

[facthunt]

Can we get small decomp valves,m10 or 12, with provision for cable operation?

[PEZBerq]

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

[facthunt]

Cable because, it rarely starts 1st kick and I can catch a stall while still rolling. XC500

[PEZBerq]

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 Good luck with the search.

[Mike52]

Changed mine to that sideways style as they are easier to reach with the long side tank.


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.

[Gday]

I've been thinking about a decomp valve for my it490. Can anyone recommend a machine shop in Melbourne for the head work?

[OverTheHill]

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.

[PEZBerq]

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.

[bazza]

is that a harley accesorie won?

[firko]

Here's a Harley accessory decompressor on my 360 Yam motor.                                                                                 
                                                                           
                                                                           

[dirtrumpy]

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