decomp stop moves to red alert

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Taffy

Taffy

Joined
Nov 20, 2001
Messages
17,028
Location
Ely, England
in 6 months i've had three decomnp stop bolts snap. two have smacked the engine about and the third one didn't. pure and utter luck!

this i believe is an age and fatigue related problem so it moves "up the charts".

every chance you get, change the bolt sat in the camwheel and i'll have a check of whether you can go larger with it.

oddly enough, they don't snap at the head of the bolt but as it enters the nut which should tell you that in order to make sure that they never come loose....... somebody has given them an extra tweak and that has stressed the thread as it enters the nut.

as usual, i think that over engineering it via a bigger bolt is the real answer.....

the annoying tyhinkg is....it's not even needed! 1mm later and the decomp stops on a cam sprocket bolt head anyway!

regards

Taffy
 
Does the bolt cause any balance issues ? Is a balanced cam chain sprocket a better sprocket?
 
sure!

but first you stop the decomp lobe and then afterwards you balance it all up. you've still got to do what's mechanically right for the bike. it's also only half engine speed.

BTW, i guess even your personal address has stopped taking my emails now eric!!!!

regards

Taffy
 
Taffy said:
sure!

BTW, i guess even your personal address has stopped taking my emails now eric!!!!


Taffy
Click to expand...

I think it may be time to take your computer in for a diagnostic. Are you running virus protection software? You may have caught a cold.
 
Taffy why would one still be running a cam sprocket that could cause a failure of

such devistation? The year of units that use said sprocket should by now need updating!

This item should be in the dumpster,this will also help with major expence for the unlucky!
 
husabutt said:
Does the bolt cause any balance issues ? Is a balanced cam chain sprocket a better sprocket?
Click to expand...
Spun mine in a drill a few weeks back & it shakes like all hell when the flyweight flips out! Losing the stop bolt would only improve the balance.
 
BOSS said:
Taffy why would one still be running a cam sprocket that could cause a failure of

such devistation? The year of units that use said sprocket should by now need updating!

This item should be in the dumpster,this will also help with major expence for the unlucky!
Click to expand...

you're up late?

boss

i have yet to see a much newer bike than '05 and they all have this nut and bolt affair.

i'll look out for the updated part. the people i'm dealing with have never had anything upgraded whatsoever! so the chance of this being changed is zilch!

regards

taffy
 
Was the decomp stop bolt eliminated or replaced with an updated stop or cam gear?
 
i trust that that was addressed to boss coz i don't know as you know....

regards

Taffy
 

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It appears the decomp stop bolt is not used in 2007.

I can't seem to download my own attachment. If no one else can see it just download the 2007 entire parts manual from husaberg.com.
 

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No bolt on my 04.
Faktor had the 1 piece stop come off his sprocket as well I believe.
I don't really see the need for the stop bolt either as Taffy states 1 mm more and it will hit the sprocket bolt, I asked some KTM mechanics about this but they hadn't tried going without it and I didn't want to be the first.
 
but craigy, think about it, if they've snapped ages ago and the engines have been running fine ever since: isn't the testing done for you? inadvertantly or not? the camsprocket bolt can only undo - it can't snap and with the amount of loctite on mine.....sheesh!

regards

Taffy

regards

Taffy
 
Craigy said:
No bolt on my 04.
Faktor had the 1 piece stop come off his sprocket as well I believe.
I don't really see the need for the stop blt either as Taffy states 1 mm more and it will hit the sprocket bolt, I asked some KTM mechanics about this but they hadn't tried going without it and I didn't want to be the first.
Click to expand...

Yep, Faktors "updated" cam gear decomp stopper (05) broke and caused him an expensive repair.

Talking to a Husaberg dealer who became aware of Faktors problem has since found a few others in the process of failing- so it seems faktors was not and will not be an isolated incident as the "updated" part ages and fatigues.
 
Taffy said:
but craigy, think about it, if they've snapped ages ago and the engines have been running fine ever since: isn't the testing done for you? inadvertantly or not? the camsprocket bolt can only undo - it can't snap and with the amount of loctite on mine.....sheesh!
Click to expand...

If my bolt had come all the way out I would have known but at the time it was loose but still hanging in there. This was in 2002 with my second RFS and I spoke to a few shops, most didn't even know the bolt was a problem.

Interestingly we used to safety wire and loctite the cam bolts when I was racing Supermono as they had a bad habit of coming loose in the Husky 610 engines we were running.
 
Ok, so I went about installing the updated decomp mechanism. First thing I noticed is the decomp face toward the stop and cam bolt is not machined the same. The old style has a concave shape that allows it to miss the cam bolt head. Then, after installing the updated version, I notice that when it is rotated toward the stop bolt, it actually never contacts the stop bolt, instead it hits the cam bolt first. So, looks like the stop bolt doesn't need to be there as the decomp never actually contacts it.
 
My belief is that utilising the cam sprocket retaining bolt as the decompressor stop MIGHT ultimately lead to failure in the long run...

why?? the original decomp stopper bolt is placed at the outer periphery of the cam sprocket- where it stops the decomp at its heaviest point when under centrifugal force..

by using the cam sprocket retaining bolt instead, there is a lot of "leverage" placed against the area where decompressor weight and round shift join as centrifugal force at the heaviest point of the weight uses the cam sprocket retaing bolt as a pivot point to add stress at this point.

My gut feeling is ultimately we MIGHT be seeing reports of decompressor weight failure at the weight/shaft junction when the cam sprocket retaining bolt is used as the decompressor stop.

I think Taff nailed it earlier- the original stop bolt fails due to fatigue and /or coming loose.
Keep it fresh at every oppurtunity with a 12.9 rated replacement, and use the "peen method" to stop it undoing as the dealer I know does and it wont give too many issues.

And yes, it should be on the "RED ALERT" list for sure.
 
ausberg

i think that a 4mm threaded bolt being battered is destined to break across its neck. given that or the shaft weight junction i would say that the relative strength of one to the other must be double as it's cast as one peice with no inherent break point.

we're now seeing fatigue and faliure in the older engines. we've just got to accept it.

regards

Taffy
 
Based on what I see when installing the new decomp bolt is, it doesn't use the decomp stop bolt on the old cam gear, due to the new profile. It's a hair away from contacting it, so contacts the cam sprocket bolt anyway. So you either change the washers on the stop bolt, mod the decomp profile to match the older, leave off the stop bolt, or change the cam sprocket to the new style.

Also, your mass seen by the stop bolt is the same as the mass seen by the cam sprocket. You've got to look at it as an entire assembly. Actually, the impact energy at the sprocket bolt will be less than that seen by the decomp stop bolt since by moving the contact point down the radius of the decomp mechanism; same with the force applied at that point as well.
 

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