Decompression valve information

asteroid500 · Post by **asteroid500** » February 19th, 2010, 9:34 pm

Has anyone got any detailed pictures or drawings on the "best" placement of a decompresion valve in the head.
1 head is a ML3E-1...Engine#5802407
& the other is a HF-1?...Engine#5500048

I just bought a pair of screaming eagle decompression valves $150.00 @ mates rates. there were no aftermarket ones availible to me in the country

JBaze · Post by **JBaze** » February 19th, 2010, 9:43 pm

If they are anything like the ones Roosty uses, check my 97 thread.

r1yfz · Post by **r1yfz** » February 20th, 2010, 12:03 am

holly hell, $150 !! i paid $18 a peice for mine in the states!...there not easy to pain to put in! you going to hit the water jacket and come up with you own way of filling it... might want to have the head decked when your done as the haet from welding could possibly warp it.

asteroid500 · Post by **asteroid500** » February 20th, 2010, 3:48 am

welcome to Australia

http://www.youtube.com/user/500bigbore · February 20th, 2010, 5:54 am

the first head casting ends in E, not R or N?
the other head is an 85 or 86, you'd have to check the step to confirm.

Theres alot different waterjacket in the heads, about where that button is on the ml series head is where i install it, i have the short valves tho, thread is only 10mm long, usually the screaming eagle ones are 15-20mm and they leak after a while.

bearorso · Post by **bearorso** » February 20th, 2010, 6:27 am

For $250 AUD, you would have got my in head, automatic decomp (no levers to pull, no buttons to push). The price includes return freight in OZ, carb mods for the vacuum fitting, decomp unit and as an extra, a stainless,'wing nut' idle screw. I also do a 'wing nut' air screw modification for another $25 AUD.

I posted a thread about this mod in 07, I think, on CR500Riders - soon after, others started to do in head decomps. Not an original idea from me, but the fellow I talked with about it had never done a 500, and wasn't interested / couldn't do one. So I did my own. I've done quite a few since then. It works well, and you don't have to think about it. You just flip the KS out and kick the bike over . It allows this old man , with end stage arthritis, synthetic cruciate ligaments and no knee cap to use a tiny , 150mm long KS lever, with no problems in starting.

Bear

asteroid500 · Post by **asteroid500** » February 20th, 2010, 4:51 pm

Bugger bear....i went to both sites serched Decomp valve, Decompresion valve and came up very short of threads. Also where are all or any of the pics of these devices. you still doing them

Roosty i love your conversion but its out of my price range at the moment.
Plus it would be good to do it in Australia so i can share the love.
The head " head casting ends in E, not R or N?" there the only markings on it.

WHAT I DO NEED IS A EXACT SPOT TO PLACE THIS THING.

http://www.youtube.com/user/500bigbore · February 20th, 2010, 6:01 pm

thats an 85-86 head, only the step at the chamber will determine, same profile as an N head, you need to be more outboard on that sucker. i'll see if i stil have it plotted on the machine, i use a fixture that locates off a center for either head

asteroid500 · Post by **asteroid500** » February 20th, 2010, 7:17 pm

your the man...i PM'd you trice but you never recived it so i went global....by the way i no longer work at the Ford motor car dealership.

JR650 · Post by **JR650** » February 22nd, 2010, 7:09 pm

this might help, 85 head roosty did for me last spring

cant recommend his work enough, starts like a real hot 250 with the 250 kicker on it.

asteroid500 · Post by **asteroid500** » February 25th, 2010, 12:08 am

OK i'm thinking of going the KX500 way of things.

I've got the tooling and materials required

This is were i'm thinking of going in.

what does the board think.

bearorso · Post by **bearorso** » February 25th, 2010, 12:51 am

Even I find it difficult to get the thread - don't remember the heading I put it under. I've got bugger all pictures saved - I don't take pics, generally, but here's some.

This is when I had the loop around alloy radiator hoses ( so no, those piddly little coolers you can buy aren't worth shit):

LH side view:

This is with the fans and radiator cages I made:

The red RTV holds on a protective strip of rubber to guard the old IMS tank from the decomp, when it gets pushed inwards by my leg / knee braces - just in case insurance basically, as is the tape over the vacuum hose fitting.

This is the short Gas Gas lever I use - legs don't bend, so much so, I use a LHRB :

That lever now has a longer foot piece added so it's easy to find, and your foot can't go anywhere:

I still do them, I don't try to push them, just word of mouth usually. I did one in a rush for a fellow before Xmas, and haven't heard from him - I was concerned that the SH ignition he has, with the 'rabbit kick' requirement would be a problem. I think he got the shits when he was charged a dishonour fee by his bank when he missed a number from my bank account that I told him over the phone - a number plastered right on my keyboard in front of me. 2 others since then, but I'm still waiting on payment from one of them - farrk, even just a few months from 50 I'm still too trusting

asteroid500 · Post by **asteroid500** » February 25th, 2010, 4:12 am

Bearso...thanks for the pic's....thermo fan hey....your kicker looks good..how much...do what i do...dont deliver till they pay.

gregrobo · Post by **gregrobo** » February 25th, 2010, 4:20 am

we have a decomp planned also we picked up the largest stihl chainsaw decomp they made for i think 20 bucks sould i add we dont know if it will work yet but hey worth a shot

asteroid500 · Post by **asteroid500** » February 25th, 2010, 4:32 am

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.

gregrobo · Post by **gregrobo** » February 25th, 2010, 4:36 am

it has potential i dont have a spare head to look at tho so cant say if it work or not

http://www.youtube.com/user/500bigbore · February 25th, 2010, 4:42 am

without blocking the waterjacket, the cr head doesnt have meat arround the stud holes like the kx

donovan35 · Post by **donovan35** » February 25th, 2010, 12:40 pm

the cr has more meat around stud than kx

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donovan35 · Post by **donovan35** » February 25th, 2010, 1:00 pm

got mine fitted 125usd inc decomp valve and head skimmed , brillant job, highly recommend the guy that did it, cost me 55usd to send three heads from US to uk[,done2xKX 1Xcr ] you are going to have to drill the hole in the right place which can be tricky, the X you have marked is going through the water jacket which will not work and it look close to exhaust
mine is going to be fitted to gen1 af and is angled back to miss the frame by 2 inches

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http://www.youtube.com/user/500bigbore · February 25th, 2010, 1:46 pm

theres 4 heads before that casting #

asteroid500 · Post by **asteroid500** » February 26th, 2010, 5:44 am

Hey Donovan...glad you got some good pic's, workmanship looks awsome...like to know how he linished the welds, you can barley see them.

As rootious said there are plenty of different heads though in the CR500 range.
I still recon it could be done off the side, it seems to me to make using it so much easier then ontop of the head.

http://www.youtube.com/user/500bigbore · February 26th, 2010, 6:39 am

thru all the heads i've welded i've noticed that most of them have carbon buildup out in the edge of the chamber if the jetting isnt on the mark, having the decomp in the pocket means its always clean, nothing to soot up the valve or passage

seanmx57 · Post by **seanmx57** » February 26th, 2010, 5:15 pm

I'd clean that valve/passage 100X (or fix the jetting) to have it on the side vs near a hot pipe.

asteroid500 · Post by **asteroid500** » February 26th, 2010, 9:58 pm

i agree with both of you...i guess for myself i'd rather just reach down instead of down and in to activate it.

gregrobo · Post by **gregrobo** » February 27th, 2010, 1:14 am

i like the idea of using the hot start lever to activate the decomp there have been some good conversions done in that department

BannedCR500Riders.com

Decompression valve information

Decompression valve information