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dutch clog decomp - a must

Taffy

Taffy

Joined Nov 2001
17K Posts | 774+
Ely, England
just done three bikes with the later decomp that looks end on like a dutch clog. all three bikes kick over like a 2-stroke. truly a break through.

at just £14 or so in the UK i think that virtually no top end work should be done without fitting it.

anyone else besides ned felt the difference and agree?

regards

Taffy
 
Taffy said:
just done three bikes with the later decomp that looks end on like a dutch clog. all three bikes kick over like a 2-stroke. truly a break through.

at just £14 or so in the UK i think that virtually no top end work should be done without fitting it.

anyone else besides ned felt the difference and agree?

regards

Taffy
Click to expand...

Hi Taffy,

Do you have a picture and part number of it?

Regards,

Joe
 
i took photos and they were out of focus! mickey mouse camera i guess!

ill try and email you some which you can put up or lose.

regards

Taffy
 
I take it, this is the most current decomp design, '04-'08 bikes? Which is good, since I've got to install a new auto-decomp due to my current being worn away.
 
Taffy said:
i took photos and they were out of focus! mickey mouse camera i guess!

ill try and email you some which you can put up or lose.

regards

Taffy
Click to expand...

Taffy, your pictures came out great, here they are after cropping them for the web site.

Remember guys, to click on the actual picture once more after it pops up to get the best focus and detail of the end of the decomp. As Taffy said, you can see the shape as kind of like a Dutch Clog (wooden shoe).

Regards,

Joe
 

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thanks joe

they were in the camera just 30 minutes ago here in the UK. sheesh1

here is a link to this not long ago joe. go to the third podt down and to Ned37's second and third photos.

it is VERY apparent that husaberg have decided to make the decomp work as far in advance as they can. thus the lump is well forwards.

http://www.husaberg.org/index.php?name= ... highlight=

regards

Taffy
 
here's more on the auto decomp old vs new. attached are a couple of pics that show the old style to go along with taffy's new style pics. to me the difference in the tip is subtle at best, but if you compare them, the flat for the old spring sits above the peak at a right angle and the new style uses a groove for the spring which sits on the front side. so if you're going to use the new one, get the new spring as well
 

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Taffy said:
just done three bikes with the later decomp that looks end on like a dutch clog. all three bikes kick over like a 2-stroke. truly a break through.

at just £14 or so in the UK i think that virtually no top end work should be done without fitting it.

anyone else besides ned felt the difference and agree?

regards

Taffy
Click to expand...

Hi Taffy,
Bear with me because I'm slightly confused about where to go next....
My 03 501 is still hard to start (although getting better) my battery is not a Yuasa but puts out the same starting current according to the battery testers measuring device - so its not that..
I've upgraded to the 04 auto decomp device. But not the dutch clog yet...
I've just put in the Yam R6 starter which is an improvement.
Its running on 5w 40 oil - the weather is about 14C
I have adjusted the kickstart decomp to factory specs
valve clearances are correct

Symptoms:
The bike sometimes gets 'stuck' on the kickstart - I get part way down the stroke (not far) and the kick gets very very tough.
Sometimes On electric start (even when hot) the bike has a real problem problem getting over TDC (im presuming) as it gets 'stuck' see above. Sometimes not - it spins over well and fires.
---
If I introduce a little manual decomp (with the kickstart lever just actuated - my handlebar lever has a broken perch.... ) the engine spins over very easily, if I then release the kickstart it will either start immediately or revert to getting stuck - or will spin over as it should do and start. I'm presuming due to these symptoms Ive got a problem with decompression somewhere in the mix - but where is it - I cant fathom - all thats left I think is the dutch clog decomp fix...

But, - I'm wondering if a change to the new dutch clog decomp and spring will actually make any difference (to the kicking at least) - given the pain of waiting for parts here in NZ and the hassle fitting it (how DO you get that cam out??? :-0) - I've read your posts but am confused a bit - does the dutch clog really make that much diff on kickstarting? I'd surmised that it was out of the circuit when trying to start on the kickstarter due to the decomp cable (and associated valve lifting device) attached to the kickstart taking over from the cam mounted decomp device??? Please could you explain how this system works (in words of 1 syllable :) ) to me?

Please can you publish the part number of the Dutch clog and its assoc spring?

Thanks for any helpful advice in advance!
cheers
James
 
jcsh said:
Taffy said:
just done three bikes with the later decomp that looks end on like a dutch clog. all three bikes kick over like a 2-stroke. truly a break through.

at just £14 or so in the UK i think that virtually no top end work should be done without fitting it.

anyone else besides ned felt the difference and agree?

regards

Taffy
Click to expand...

Hi Taffy,
Bear with me because I'm slightly confused about where to go next....
My 03 501 is still hard to start (although getting better) my battery is not a Yuasa but puts out the same starting current according to the battery testers measuring device - so its not that..
I've upgraded to the 04 auto decomp device. But not the dutch clog yet...
I've just put in the Yam R6 starter which is an improvement.
Its running on 5w 40 oil - the weather is about 14C
I have adjusted the kickstart decomp to factory specs
valve clearances are correct

Symptoms:
The bike sometimes gets 'stuck' on the kickstart - I get part way down the stroke (not far) and the kick gets very very tough.
Sometimes On electric start (even when hot) the bike has a real problem problem getting over TDC (im presuming) as it gets 'stuck' see above. Sometimes not - it spins over well and fires.
---
If I introduce a little manual decomp (with the kickstart lever just actuated - my handlebar lever has a broken perch.... ) the engine spins over very easily, if I then release the kickstart it will either start immediately or revert to getting stuck - or will spin over as it should do and start. I'm presuming due to these symptoms Ive got a problem with decompression somewhere in the mix - but where is it - I cant fathom - all thats left I think is the dutch clog decomp fix...

But, - I'm wondering if a change to the new dutch clog decomp and spring will actually make any difference (to the kicking at least) - given the pain of waiting for parts here in NZ and the hassle fitting it (how DO you get that cam out??? :-0) - I've read your posts but am confused a bit - does the dutch clog really make that much diff on kickstarting? I'd surmised that it was out of the circuit when trying to start on the kickstarter due to the decomp cable (and associated valve lifting device) attached to the kickstart taking over from the cam mounted decomp device??? Please could you explain how this system works (in words of 1 syllable :) ) to me?

Please can you publish the part number of the Dutch clog and its assoc spring?

Thanks for any helpful advice in advance!
cheers
James
Click to expand...

James,
I simply ordered mine as a KTM RFS part (which is what they are originally)

- 590.36.016.000 (decomp)
, 590.36.017.000 for the spring.

You will probably find your local KTM dealer has them in stock-mine did.

But as far as I know, if you have the 04 decomp then it should be that part already??

There was a post on here a while ago suggesting that the early springs dont quite fit the later decomps properly- perhaps yours is not returning properly sometimes? just a thought.
 
I've upgraded to the 04 auto decomp device. But not the dutch clog yet...
Click to expand...
i'm confused, because the 04 decomp is the dutch clog.
there are other factors which will keep it from working smoothly, one of them is valve clearance. if the exhaust is a bit too loose, the decomp won't get full lift and will do as you describe. if the rocker follower bearing is loose radially or axially, you will have variable clearances and thus the same problem.
do you have the kickstart decomp connected? does your model even have one? i found it all much easier to deal with when it was disconnected.

ausberg, you beat me to the punch, had to go chase down the dog mid sentence.
 
that loxking effect james is when the decomp doesn't get rid of enough charge and you carry on pushing over the engine. the auto decomp is just a bump that gets rid of some of the charge.

how it works
it has a spring which forces the decomp bump to be proud and release the compression. however, if you just kicked the bike or even ran it, at quite low revs the decomp lays flat and you keep all the gases in the cylinder.

so if i ride into the yard and stall the engine - guess where it stops?

right as the piston comes up on the compression stroke. the cylinder is full of charge/mix and sits there like that.

you then go to kick it and break yer phuckin leg!

same applies to kicking it over. if you kick it gently enough the decomp will lay flat and you again get a full charge.

IN YOUR CASE THOUGH I'M GOING TO SUGGEST THAT THE SPRING HAS LOST IT'S STRENGTH OR BECOME UNBOUND. the only way to check is to remove the rocker cover and flick the decomp. it should be quite strong at whipping the decomp back into the axle of the cam.

then at the same time you can check the condition of the lobe itself and which year you have.

go into upgrades, red alert and tuning in the doc and there are some great photos there.

regards

Taffy
 
Taffy said:
that loxking effect james is when the decomp doesn't get rid of enough charge and you carry on pushing over the engine. the auto decomp is just a bump that gets rid of some of the charge.

how it works
it has a spring which forces the decomp bump to be proud and release the compression. however, if you just kicked the bike or even ran it, at quite low revs the decomp lays flat and you keep all the gases in the cylinder.

so if i ride into the yard and stall the engine - guess where it stops?

right as the piston comes up on the compression stroke. the cylinder is full of charge/mix and sits there like that.

you then go to kick it and break yer phuckin leg!

same applies to kicking it over. if you kick it gently enough the decomp will lay flat and you again get a full charge.



IN YOUR CASE THOUGH I'M GOING TO SUGGEST THAT THE SPRING HAS LOST IT'S STRENGTH OR BECOME UNBOUND. the only way to check is to remove the rocker cover and flick the decomp. it should be quite strong at whipping the decomp back into the axle of the cam.

then at the same time you can check the condition of the lobe itself and which year you have.

go into upgrades, red alert and tuning in the doc and there are some great photos there.

regards

Taffy
Click to expand...

Ok, Thanks Taffy and you others - this is helpful
I've just gone and checked the auto decomp cam shape and it seems to be teh old shape - so when I asked for thr new one last year they sent me teh old shape again! Doh!

- but..
It looks like this auto decomp device was actually not used when trying to start on the kickstarter due to the decomp cable (and associated big bar type valve lifting device) attached to the kickstart mechanism taking over from the cam mounted decomp device and rendering it not used??? Is this right? If it is then the auto device is only 'in circuit' for the electric start - so shouldn't make any diff when kicking.. what do you think?

Anyway I will now go and order the new shape parts listed above and try again :)

Thanks very much all!
Cheers
James
 
Actually, looking at the new (RFS) decompressor in an old ("53") cam makes me wonder 2 things-

1. How long is the tip going to last as it is only being contacted on a very small portion of ts overall length.

2. Will there be spring (decomp) issues given that the decompressor unit has nothing to control its float - other than the spring- doesnt the cam bearing help retain them too??

I think someoneelse also mentioned the length issue too?? :?
 
the spring is now in a trench. you can see that in the photos i hope so the decomp is continually being forced against the end of the slot in the exhaust lobe.

i can't say how long the tip will last BUT it has a low front edge which is a new idea/effort. the small area has always been a problem.

regards

Taffy
 
i've just done the mod with a few issues. the main one was the length of the shaft on the decomp shaft. i could not get the spring to work properly as it was squashed in there and kept binding up. i had to cut about 3 coils off the spring and re bend the end of the spring to make it work. it works now but is a bit inconsistant with starting off the e start. sometimes it fires and sometimes it doesnt but it is kicking straight away with no problems and as said before is very easy to kick over.
my other issue is the length of the shaft that is comming into contact with the roller is less than the standard shaft and i can se this wearing very fast.

i'm not quite sure why it's not starting well off the button??!! could i have bent the spring too tight and the decomp wants to swing out but can't because the spring is too tight?? has anyone wound their spring too tight?? what happened??!!
 
the spring is now too soft. i can't understand how you had these issue with the shaft being too short etc.

regards

Taffy
 
i didn't measure it but at a guess it was 3mm shorter in shaft length. i used the ktm part numbers from an earlier post. maybe i bought the wrong part.
i didn't think that the spring could be too soft because it turns over easy but just doesn't want to fire.if it was too soft wouldn't it be fighting against compression???!!! when the bike was warm it did seem to work better but still refused to fire sometimes. battery is a yuasua(spelling???) and is about 6 weeks old so that is not the prob. when the e start didn't work it would kick 1st or 2nd kick. and i could prob kick it over by hand now if i wanted to!!


was your later decomp the same length as the old????? could there be two different later decomps????????????????????????????????????
 
the new decomp is 36.8mm and the old one is 39.5mm but the new spring is 3mm narrower than the old spring! the old spring has a dog leg shape at the end whereas the new one goes straight across the middle!

i think you might have a new decomp and an old spring?

i've not experienced any trouble with the new set up....

regards

Taffy
 

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