Decompression valve information

donovan35 · Post by **donovan35** » February 27th, 2010, 4:43 am

got a few heads and secondhand pistons here dont see any more carbon in the outer area than centre,
seanmx57 so u are trying to say its going to block up 100x faster in the place i have used, wheres the hot pipe u are refering to??

CR500R7 · Post by **CR500R7** » February 27th, 2010, 6:16 am

I'm sure he meant he would rather clean the valve / passage 100 times and have it on the side of the head, than to have it placed near a hot pipe.

The hot pipe would be the Exhaust pipe.

Corrected, Thanks seanmx57.

seanmx57 · Post by **seanmx57** » February 28th, 2010, 8:16 pm

Hot pipe, the fmf, pc stock or what ever is the "best"

CR500R7 · Post by **CR500R7** » February 28th, 2010, 10:29 pm

seanmx57 wrote:Hot pipe, the fmf, pc stock or what ever is the "best"

The "best" pipe is the one that is on your bike, any other pipe is completely useless until it is on your bike.

asteroid500 · Post by **asteroid500** » March 5th, 2010, 10:33 pm

OK...
I finished off my D-comp valve today.

I decided to go in here.

Using a 2.5mm bit we set the head up in the vice and made sure it was sqare. i used the 2.5mm bit as it was the only one i could get that was long enough.

Clamped in place using 2 pieces of rod so as to press the face of the head against the sqare side of the vice.

Drilling the hole, we went in slowly and with the odd spray of WD-40 to keep it from binding on such a long hole, also drawimg the bit all the way out every now and then to spray the alloy of the bit with the WD-40

Now i used a 14mm blade bit to recess the side of the head so the new treaded piece could sit sqare onto the head, you dont have to do this but we did because it was easier to hold it in place to weld.

Recessed.

Dummy fitted prior to welding.

Clamped in place, alot easier with the recess done.

Steve tig welding it in place. (thanks Steve, my welds suck)

Final welds completed.

A quick acid bath.

And finaly back were it belongs, i recon it looks good, is functional, and easy to get to, you've gotta flick out your kick start any way so now i can hit the decompression valve while i'm at it.

seanmx57 · Post by **seanmx57** » March 6th, 2010, 10:22 am

IS there a reason to do it on the right side? I don't see why anyone would want to put it near the pipe. The left side has no obstructions, especially ones that could burn your hand.

Nice work regardless!!

donovan35 · Post by **donovan35** » March 6th, 2010, 10:47 am

nice job mate well done , looks a good quality valve,
you mentioned u did not have drill long enough , the hole2valve in mine is probably only 30mm long so i take it u drilled to a different point in combustion chamber? probably going to be a bit more of a risk weaking the squish area of head [also more cc ] . have u tried it yet? still crap weather here in uk so i did not get a chance to fit mine.

donovan35 · Post by **donovan35** » March 6th, 2010, 10:50 am

seanmx57 wrote:IS there a reason to do it on the right side? I don't see why anyone would want to put it near the pipe. The left side has no obstructions, especially ones that could burn your hand.

Nice work regardless!!

best position on gen1 af , can visually see it setting on bike , simple to press

seanmx57 · Post by **seanmx57** » March 6th, 2010, 11:42 am

donovan35 wrote:
seanmx57 wrote:IS there a reason to do it on the right side? I don't see why anyone would want to put it near the pipe. The left side has no obstructions, especially ones that could burn your hand.

Nice work regardless!!

best position on gen1 af , can visually see it setting on bike , simple to press

Gen 1's have exhaust pipes too.............

donovan35 · Post by **donovan35** » March 6th, 2010, 1:25 pm

seanmx57 wrote:
donovan35 wrote:
seanmx57 wrote:IS there a reason to do it on the right side? I don't see why anyone would want to put it near the pipe. The left side has no obstructions, especially ones that could burn your hand.

Nice work regardless!!

best position on gen1 af , can visually see it setting on bike , simple to press
Gen 1's have exhaust pipes too.............

who said gen1 dont have exhausts ?
i think both of us decided to pick a awkward place to put valve!! [ even though it is simple to press there]
I am now very concerned about starting my bike after a ride, how am i going to touch the KICKSTART without burning my hand off the HOT PIPE exhaust???????

CR500R7 · Post by **CR500R7** » March 6th, 2010, 3:39 pm

donovan35 wrote:I am now very concerned about starting my bike after a ride, how am i going to touch the KICKSTART without burning my hand off the HOT PIPE exhaust???????

Try wearing some gloves.

asteroid500 · Post by **asteroid500** » March 6th, 2010, 5:07 pm

All good fellas,
I put my valve were "I" thought it best for my 99G-1/AF.
The right side, and were i put it by far is the clearest and safest place on a G-1.

Donavan is right,
there are more chances of "BURNING" your hand reaching down to the kicker then pushing in your D-comp valve.

The spot i placed my valve is clear from any and all obstructions, the frame is 24mm from the base of the valve to the frame, 20mm from the black rubber top of the valve to the frame, 60mm from the top of the valve to the radiator shroud, & 90mm from the top of my OEM expansion chamber.

The black line in the bottom of the picture is the exhaust.

Now the Left hand side for example is full of shit, coil,carby,choke,fuel tap, i could of got it in but it would of been even more clutered down there.
Also in the name of safety, if you concerned with being burned i'd suggest wearing gloves, probably a welders longsleve glove to make sure.

Donavan, i drilled square to the face of the head, there for it exited 4mm above the band line in the squish cup.
I dont see a problem with it, i chamfered the hole so no hot spots are going to be prevelent.

No i've not kicked it over as my kicker gear is not in yet, but i could turn the motor via the gear box and a cordless drill, worked easy.

FYI...14mm solid alloy rod.
...9mm drill bit
...1.0 metric fine tap
...Screaming eagle decompresion valve
...14mm blade bit
...1/2 a can WD-40

CR500R7 · Post by **CR500R7** » March 6th, 2010, 8:33 pm

Looks like a really nice job Man.

How did your Chinese vise hold up.

donovan35 · Post by **donovan35** » March 7th, 2010, 4:42 am

any pics of where the hole enters the combustion chambers ??
i know you a bit concerned about people saying it would block on the outer edge just think the hole in the outer edge is a safer option [ could also make it harder to do any head work at a later date [recutting squich band]
saying that due to to the shape of the head it should work ok ,
mine got a garley exhaust pipe so space it tigher bit than yours but still got loads room to press valve
good luck with the rest of the build

asteroid500 · Post by **asteroid500** » March 7th, 2010, 5:42 am

Chines vice.....
Wok veby whelll fank yu

CR500R7 · Post by **CR500R7** » March 7th, 2010, 9:55 pm

100hp honda · Post by **100hp honda** » March 9th, 2010, 9:24 pm

anybody tried it in a coolhead ?

Post by **AlisoBob** » March 9th, 2010, 10:07 pm

asteroid500 wrote: Wok veby whelll fank yu

Your friggin' nutz......

asteroid500 · Post by **asteroid500** » March 9th, 2010, 11:28 pm

Well i do scratch'm

Wheelie-Gene · Post by **Wheelie-Gene** » March 21st, 2010, 12:02 pm

Looks almost like the one I did (and posted) a while back.
I really like the quality of the stainless S&S Harley decomps.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » March 21st, 2010, 5:57 pm

coolhead needs no welding

asteroid500 · Post by **asteroid500** » November 27th, 2011, 9:33 pm

It would seem DE-comp has found itself back on the front page.......i know what i like

NightBiker07 · Post by **NightBiker07** » November 28th, 2011, 8:40 pm

asteroid500 wrote:EAT SHIT gregrobo,
Fuck i cant belive i paid $150 for 2 bloody valves.....OOOOHHHHH well.
who you colouding with...shaggy, maybe we shoul form a think tank.
what do you recon of my idea of going threw the side.

You did buy Harley parts, after all.

mr500 · Post by **mr500** » December 8th, 2011, 1:40 am

After riding all day saturday for the first time with a decomp valve.
I'm thinking it's good but not the BEST thing ever!!
The PMB stand was a WAY better investment and gets more use!
Because its hard to find TDC with the valve in ,I found it easier just to kick it normaly as it starts with one smooth kick anyway.
Maybe if I was on the side of a nasty hill and really rooted I'd use it.
Just nice to know its there and I'm not getting younger...

2strokeforever · Post by **2strokeforever** » December 8th, 2011, 10:30 am

Because its hard to find TDC with the valve in

you can find tdc, then push the button

after a while you can tell exactly where tdc is with the valve pushed, by feel, and the sound

i really like it for bomb starting, or if you stall but are still moving, hit the button with your boot and let clutch out, it can be done really fast

BannedCR500Riders.com

Decompression valve information