Dutch clog decomp, spring and cam

husabutt · Aug 23, 2009

The decomp return spring on my 1997 600 is now F.U.B.A.R.ed as I have tried to bend it to make it work. The pranged part would not grip the flat part of the decomp very well and slips barely staying in place neting little to no spring tension. If I order another stock decomp spring which was the same part # from 1995-2000 I will probably get the same marginal to not working results.

So my questions are:

Will the newer decomp spring, 2004-2008 fit the older decomp?

Can I use the newer Dutch clog decomp and spring in this 1997 cam if the cam is machined as shown in "the doc"?

If I wanted to use the newer decomp, spring and cam which cam should I use that would be the most beneficial to starting (2008 650 cam?).

Since the KTM RFS motor is an extension of the pre-2001 motors would the KTM decomp spring, part # 4383443-001 work and possibly the decomp itself, part # 4383442 with the 1997 cam?

berger · Aug 23, 2009

Can you even use the late model cam? Being the waterpump is driven off of it on the early motor.
Could you modify the profile of the old style decompressor to match the new style (weld it up and grind to the new profile)?

schultzy · Aug 23, 2009

Check the posts here for the decomp thread. For my 98 I used the part numbers from the thread and used the new decomp and spring on my 98 600.I had confirmation from Taffy that it would work. I still have the old cam chain sprocket and needed to do some minor grinding on the decomp to get the nub to stand properly on the cam. The spring I had to take a few turns off of it as it was longer than my old one. I then installed it, gave it 1 turn of tension and slipped it into the groove. I used a dab of silicone to help keep the spring from slipping.
I saw very little difference in my old to new decomp. I think the steel sprocket must change things and I have no experience with that yet.
Cold, it starts in 2 or three kicks. warm, starts first spin of the motor from the button. Awsome!

Taffy · Aug 24, 2009

i would fit a later cam from a KTM they are basically the 53 profile but with the flanks still concaved but softened like the 08 cam. the waterpump shaft will be fine and you even have the bonus that the decomp will go straight in and the shoulder doesn't need machining. i as has been said, the only difference is the spring, you need to get rid of about 4 turns of it.

why not go to dual valve springs while you are there?

regards

Taffy

husabutt · Aug 24, 2009

Taffy said:
i would fit a later cam from a KTM they are basically the 53 profile but with the flanks still concaved but softened like the 08 cam. the waterpump shaft will be fine and you even have the bonus that the decomp will go straight in and the shoulder doesn't need machining. i as has been said, the only difference is the spring, you need to get rid of about 4 turns of it.

why not go to dual valve springs while you are there?

regards

Taffy

I have the head and cylinder off now. I never noticed it before (or gave it any thought) but it has dual valve springs from the factory. Checking the manual it appears that first generation motors came that way since 89 and at least up to 1997 and probably to 2000.

Taffy, do you think that going to the new DVS for the newer bikes would be of benefit? I was absolutely thinking of using the DVS set up as part of the top end rebuilt.

What if I used the KTM cam with the KTM decomp and spring? A quick check shows that the same decomp was used for all of the KTM RFS motors.

Taffy · Aug 24, 2009

i believe it was 97 or 98 (end of) when they changed. the '99 i stripped had conicals.

yes sure go with the decomp for your new KTM cam, that makes sense for sure. i wouldn't bother going to later DVSK's unless someone can prove the seat pressure is ridiculously strong on your set up so a later set would then be beneficial.

regards

Taffy

husabutt · Aug 24, 2009

A quick search onthe KTM parts fiche shows that the RFS motor uses DVS as standard equipment (I searched 01-07 on select models). So I would take it that the aftermarket KTM / Husaberg kit uses different rates or configurations of the two springs to achieve superior results which may be the case with my 97?

Taffy · Aug 24, 2009

you have smaller valves, i would have thought that they would use a softer spring for your year?

regards

Taffy

husabutt · Aug 24, 2009

Taffy said:
you have smaller valves, i would have thought that they would use a softer spring for your year?

regards

Taffy

Ah........makes sense

On the exhaust valves there is a coating, possibly a heat barrier, which I mostly removed with a bronze brush and degreaser (I thought is was carbon). Can this cause a problem?

Taffy · Aug 24, 2009

that will be some form of carbon or teflon as you say. i can't see why? it's designed to continue without it i'm sure.

regards

taffy

husabutt · Aug 24, 2009

Taffy said:
i would fit a later cam from a KTM they are basically the 53 profile but with the flanks still concaved but softened like the 08 cam
Taffy

I am leaning toward using the KTM cam as suggested. Do you know which model uses the cam mentioned above or possibly have a part number?

Taffy · Aug 24, 2009

well it's been mentioned here. the number 5521 comes to mind but where and how i don't recall. yes i do. put a search in by a doppy canook named lee fryberger!!!!!! he runs 'em and loves 'em!

regards

taffy

husabutt · Aug 24, 2009

Thank you sir!

Faust · Aug 25, 2009

could you please put a pic of your stock cam?If I were you I wouldn't bother using a new cam and save my money.It shouldn't make much difference.just put a new decomp spring and go.if your decomp lobe is weared get a new decomp also.and use your stock DVSK.don't waste your money.if your cam follower bearings is fine then never ever think of changing your stock DVSK.

fryguy · Aug 25, 2009

Taffy said:
well it's been mentioned here. the number 5521 comes to mind but where and how i don't recall. yes i do. put a search in by a doppy canook named lee fryberger!!!!!! he runs 'em and loves 'em!

regards

taffy

just 'cause it takes me 4 days to respond...does that make me dopey????? sshheeessshhhh

I'm not sure I can add much here. The only "KTM" cam I've ran was in a 380 kit I built, which I did not run back to back with the std cam. It was suggested to me to run by 'reliable sources'.... and it did work good. I've never had a pre 01 motor apart..so I"m afraid any suggestions on your predicament Eric would be pure speculation and not worth trusting, I'm sorry to say.

Is it possible to cross reference the old Husaberg part numbers to the current # system...then see where the similarities lie?? Perhaps then you could see common cams?

all the best to you

cheers

fry

husabutt · Aug 30, 2009

Faust said:
could you please put a pic of your stock cam?

Faust: The cam will be out of the bike until I receive the water pump seals, so if you would like a picture taken at a different angle just let me know.

schultzy · Aug 30, 2009

on my decomp spring I put a dab of silicone on the other side of the spring as that is where it seems to slip or loosen.
A close up of your decomp in the off and on position would be helpful for everyone!

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