Decomp valve

mr500 · Post by **mr500** » September 23rd, 2011, 10:58 pm

Have give a quick thumbs up to Larry W for the lovely job he did on 2 heads
Here's one.

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&
On the bike.

Tharrell · Post by **Tharrell** » September 24th, 2011, 4:30 am

Nice, got a pic of the inside?

mr500 · Post by **mr500** » September 24th, 2011, 6:16 am

As requested
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CR500PHIL · Post by **CR500PHIL** » October 17th, 2011, 7:43 pm

mr500 wrote:Have give a quick thumbs up to Larry W for the lovely job he did on 2 heads
Here's one.

[/url]
&
On the bike.

Beautiful - I wonder would it clear the side of my large Clarke tank.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » October 18th, 2011, 6:18 am

That head is like the ones I do also, most of the side mount ones didnt clear the big tanks, I had always installed them stair up before because of that. I did sell some side mount stuff that didnt need to be welded also.
I have a strait up install R casting head ready to go if you need one

CR500PHIL · Post by **CR500PHIL** » October 18th, 2011, 7:53 am

Roostius_Maximus wrote:That head is like the ones I do also, most of the side mount ones didnt clear the big tanks, I had always installed them stair up before because of that. I did sell some side mount stuff that didnt need to be welded also.
I have a strait up install R casting head ready to go if you need one

I still have a couple needs for upgrades throughout the fall and over the winter and this may well be one of them. I will contact you when I get ready to do this. Here is one thing I do not understand - if low compression causes difficult starting ( I experienced this first hand) then why doesn't a decompression valve have the same effect?

mr500 · Post by **mr500** » October 19th, 2011, 3:14 am

Who said its easier to start?.. Decomp means it's only easier to Kick!

Maybe its cos the mixture is going out the decomp valve and not back into the crackcase via the rings?

One thing i did notice is it's harder to find TDC wiith the valve in.
BIt like an xr400.
Better to find TDC first then push the button.

Post by **AlisoBob** » October 19th, 2011, 8:24 am

mr500 wrote: Maybe its cos the mixture is going out the decomp valve and not back into the crackcase via the rings?

Gmbond · Post by **Gmbond** » October 19th, 2011, 9:23 am

Although my bike needs some jetting time spent still, I find the big difference on the decomp valve is it allows the motor to spin over a bit quicker. They still like an open throttle and a damn good kick, but with my still weak right knee I'd otherwise be leaning the handguard against a tree and having to stand on the peg for every start I think.

NightBiker07 · Post by **NightBiker07** » October 19th, 2011, 10:42 am

You use the decomp to get some kick momentum before returning the full cylinder compression. if the decomp stuck on, it would never start, similar to a low compression issue.

I dont understand how these work though. A lever operated one stays open until you release the lever. but how are you supposed to kick the bike and deactivate these decompression valves? I must be missing something here

Gmbond · Post by **Gmbond** » October 19th, 2011, 11:30 am

these are a poppet style valve, you push it in and it "snaps" down...

when kicked they will stay open, but upon the first good pop or fire from the cylinder it kicks them shut. Sometimes if the bike pops/fires it will kick them shut before it starts and you need to reset the valve again to kick again. My Valve is on the right side of the cylinder head, so when i reach for the kickstarter its right at my fingertip to push in, it seems a little more natural on this side to me as i only need to use the one arm to get the kicker and the valve. Some people have rigged up cables to allow a bar mount hot start lever from a 4T to be used to bump it open, some of these setups are pretty damn sweet.

There are several different manufacturers of the valves, including some chainsaw designed ones... (STIHL)

AV&V
Goodson
S&S
Screaming Eagle
all make the same sort of style but i haven't got any clue what is best...

NightBiker07 · Post by **NightBiker07** » October 19th, 2011, 1:32 pm

Gmbond wrote:these are a poppet style valve, you push it in and it "snaps" down...

when kicked they will stay open, but upon the first good pop or fire from the cylinder it kicks them shut. Sometimes if the bike pops/fires it will kick them shut before it starts and you need to reset the valve again to kick again. My Valve is on the right side of the cylinder head, so when i reach for the kickstarter its right at my fingertip to push in, it seems a little more natural on this side to me as i only need to use the one arm to get the kicker and the valve. Some people have rigged up cables to allow a bar mount hot start lever from a 4T to be used to bump it open, some of these setups are pretty damn sweet.

There are several different manufacturers of the valves, including some chainsaw designed ones... (STIHL)

AV&V
Goodson
S&S
Screaming Eagle
all make the same sort of style but i haven't got any clue what is best...

Got it. I know the 4 stroke hotstarts will stay open as long as you hold the lever.

The more i read into these, the more i want one for my bike.

Would you have any pics of a cable rig on one of these? that would be really nice to have. I just cant visualize hooking a cable to that little thing, especially if you push IN on the button

cbx1170 · Post by **cbx1170** » November 22nd, 2011, 6:01 am

How to get a hold of Larry W? he is at lwiechman@charter.net

mr500 · Post by **mr500** » November 22nd, 2011, 4:04 pm

Don't expect to be writing pages of correspondance with Larry..

wiechman@charter.net

Gmbond · Post by **Gmbond** » November 22nd, 2011, 7:55 pm

Give him a call

815-623-8940

2strokeforever · Post by **2strokeforever** » November 22nd, 2011, 8:18 pm

if the decomp stuck on, it would never start

ya it could, mine does it every once in a while, also with a little throttle it will run with it open, i didnt pass soundtest so i held it open with my knee, and richened up the air screw, also put it in gear and kept a little load on it with the clutch, and backed away from the tent the bike was suposed to be parked under
this let me scrape thru

it wasnt too loud really, but the random bing noise coming from the pipe was pushing it over the limit
im gonna get a washer that fits between the silencer and pipe for next time in case theres issues

jbsleddin · Post by **jbsleddin** » November 23rd, 2011, 3:25 am

NightBiker07 wrote: The more i read into these, the more i want one for my bike.

I am thinking the same thing but having trouble admitting it. It's like your first AA meeting, admitting you have a problem.

http://www.youtube.com/user/500bigbore · November 23rd, 2011, 5:53 am

I started making them when I blackened my foot almost this bad...

bearorso · Post by **bearorso** » November 23rd, 2011, 7:45 pm

mr500 wrote:Who said its easier to start?.. Decomp means it's only easier to Kick!

Maybe its cos the mixture is going out the decomp valve and not back into the crackcase via the rings?

One thing i did notice is it's harder to find TDC wiith the valve in.
BIt like an xr400.
Better to find TDC first then push the button.

It bloody well should start easier. There's not much bloody point if it doesn't. It shows it to be an ill thought out design, however pretty it might be.

Does your bigger tank still fit?

I posted my Auto Decomp pics and info in July 07, on CR500riders . SH and Roosty seemed to have got into them, then.

Mine, you just kick the bike, and it goes. No levers, buttons , TDC finding, or anything to mess with. Fit any tank you want. I don't try to sell them on sites, as I've more than enough to do, but I've done quite a few for people who have sought me out. Unless I'm 'snowed under', if a OZ owner sends his parts (head, and carb) to me by Express Post, they get the finished job back, in less than a week from when they sent their stuff.

DonDDR · Post by **DonDDR** » November 23rd, 2011, 10:53 pm

It shows it to be an ill thought out design, however pretty it might be.

What is an ill thought out design? What am I missing when you say that? Its late and I might not get it right now...

Mine, you just kick the bike, and it goes. No levers, buttons , TDC finding, or anything to mess with. Fit any tank you want. I don't try to sell them on sites, as I've more than enough to do, but I've done quite a few for people who have sought me out. Unless I'm 'snowed under', if a OZ owner sends his parts (head, and carb) to me by Express Post, they get the finished job back, in less than a week from when they sent their stuff.

Id like to see your design, or sell me the plans to do myself?

BannedCR500Riders.com

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