Auto-decomp questions???

sandskipper · Oct 7, 2005

I have a question for the masses regarding the auto decompression device located on the kick start shaft and decompression lever that it actuates. I posted in another thread (Broken kick start shaft) but didn't get any responses to my questions regarding the decomp system.

Please go to the pics I have posted in my gallery by following this link (Kick shaft/Decomp pics) in order to get an idea of what i'm talking about hear.

My kick start shaft broke at the point of spline termination while on a ride last weekend. I have since taken the clutch cover off to remove the part and noticed the wear on the decompression device of the shaft as shown in the pics and also the lever it actuates (which I hope to have pics of sometime this weekend).

Thanks to all of you, I have received an answer to my question regarding the stronger kickstart shaft to alleviate the breakage at the splines.

My new question now is.... "Do I have a mis-adjusted auto decomp system that caused the wear on the shaft and lever or is this just the nature of the beast"? I apologize for not having pics already of the lever but upon close inspection it looks like it was made on a bench grinder in a five minute attempt to get the bike ready for the second heat of a race!!! No smooth surfaces, very unrefined..... like a 3 year old lawn mower blade!!! I do not believe this was caused by the normal actuation of the lever coming in contact with the decomp lobe of the shaft as those channels are unmistakably evident. Im wondering if the poor surface quality of the lever was the culprit of the wear seen on the rest of the surfaces (one bad surface leading to premature wear of the contact surface of another and so on...)and if a simple polishing of the surfaces would have prevented/prolonged the life of these parts or if my lever was just out of adjustment???

Any thoughts or ideas would be greatly appreciated?

Regards,

wildbill · Oct 8, 2005

I noticed when I had everything apart concerning my kick starter that there was quite a bit of wear on the ramp and the decompression lob (the part that passes through the case to the cable). Your decompression might have been out of adjustment but mine was not even hooked up. I would check it over good, something might be out of wack. Work it through the motion and see what it does. Hope this helps.

Maddel · Oct 10, 2005

IMHO the wear on the shaft and lever is just the "nature of the beast". :?
While removing the electric re-starter (after about ten running hours) I
found quite similar wear.
The mechanism design is a crude way to produce the auto-decomp "click".
I slightly removed the worst burr and the system worked fine for
three years now. :roll:

LINEAWEAVER · Oct 10, 2005

Nature of the beast.
May I suggest you completely remove said system plugging the shaft bore with a pipe plug. The engine will start easier with proper use of the manual lever.

Hope this helps.
Sincerely,
Dale

PS
Note the late model engines have followed my que and indeed are minus the kick de-comp.

Taffy · Oct 10, 2005

i only have the manual decomp. i've run mine like that for a season now and it's easy peasy lemon-squeezy!

regards

Taffy

threedigits · Jan 31, 2017

Can the manual decomp be actuated when E-starting, or will the piston hit exhaust valves if done ? I have not tried in fear of that, only used it to carefully adjust the kicker pass the combustion.

Taffy said:
i only have the manual decomp. i've run mine like that for a season now and it's easy peasy lemon-squeezy!

regards

Taffy

Taffy · Feb 1, 2017

yes it can be activated but the bike can't start with it activated. you can try and just suddenly 'dump' the lever but it kills the engine stone dead and never ever starts it....

the one exception, ever, in the history of the world will probably be along in a minute and leave you dazed and confused!

Taffy

ned37 · Feb 1, 2017

Khristi · Jun 26, 2017

I finally managed to break my kickstart return spring due to a hard to start 1994 FE600 engine. A question on the kick lever actuated decomp: doesn't it decomp a bit to much and for a too long duration? I have it set to the 2 +/- 1 mm the manual calls for and it seem to disengage about half way down the kick motion.

I'm thinking about fitting a manual decomp instead since the rocker cover mechanism is set up for it. I don't have the cam shaft that will take the weight/spring auto decomp.

Will I be able to kick through a complete kick motion without the decomp, after passing compression stroke TDC with manual decomp? Thoughs on this?

Taffy: Read that you remove the kick actuated decomp more or less as a rule, why?

bushmechanic · Jun 26, 2017

Hmm ?

I always started mine using the manual de Comp and e start

It worked everytime. 2008 650. Plenty of people in oz can manage it. The trick is in the timing of the release

I even removed the auto decomp on the cam for a while as it was effectively useless with the stock Spring.

This principle is employed in many many engines with obviously positive outcomes. What it allows to happen is the crank builds momentum then when you gently release the lever there is enough rotational inertia in the crank to turn the engine over and start it

Mazzokie · Jun 27, 2017

I took the advice and removed the auto decomp(3 mounth ago),i dont feel any difference in the way to start it though .
Husaberg 600fe 1995.
I use manual decomp and by the fourth or the fifth kick I got one bit of the kick movement that feels like a mechanical stop cant pass it, totally stop.
The guy(heavy one Im a light guy) I bought the bike from said that the kickaxle was replaced, I think if you are trying to go through this dead end stop before it reach the footpeg by brutal force you could break the kickaxle or someting related .

husabutt · Jun 27, 2017

The 600's up to 2000 have a helluvalot of compression. A friend that has a 99 600 used the stock decompression device and spring. He pretensioned the spring so that lever or device snapped back nicely to its resting position. He can kick start it while sitting on the bike. Taffmeisters sells a stronger spring which is not a bad idea too.

On my 97 I went to a KTM cam and used the newer 04-08 decomp and it will kick and e-start easily.

It came from the factory with the decomp spring incorrectly installed and I could never kick start it. Luckily it was an e-start model. The e-start models of that era came without the manual dompression release.

Khristi · Jun 28, 2017

Since I have it apart now and waiting for a new kick lever return spring I carefully looked at the mechanics of the kick start auto decomp.

1. Kick lever resting position is approx 11 o'clock, kick lever more or less towards clutch cover.
2. The decomp cam on the kick start shaft starts to lift the decomp actuator at 12 o'clock (rest in cam) and starts valve lift approx half past 12..
3. The engagement pawl is released from it's locking cradle at about 1 o'clock (kick start shaft engages kick start gear).
4. The decomp cam disengages at about 4 o'clock.
5. The kick lever stops towards the foot rest at about 6 o'clock.
6. One comple "normal hard" kick gives two revs on the crank/one complete cycle.

I previously had my decomp slack adjusted to 2 +/- 1 mm at the decomp axle, according to the manual his was set at compression TDC.
When having this apart, I see that there's a small rest position for the decomp actuator on the kick shaft decomp cam just before the decomp engages. I adjusted the slack in this position instead, giving more slack at kick lever rest position (11 o'clock) and less total lift during decomp. I can still push the lever by hand but I can feel a bit more resistance. I think to much decomp lift maybe makes my bike hard to start since I have been through absolutely everything at least twice and tried different choke and idle jets.

In the first attached photo you can see the decomp actuator at the cam rest position before engagement. In the second photo the decomp is in total rest, kick lever rest position (also the shaft wont return further because the pawl locks towards a raised part of the cradle). Below the shaft you see the pawl lock cradle (pawl removed but it goes in the slot on the underside of the axle).

Now I just hope the new spring arrives before the weekend.

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Auto-decomp questions???

sandskipper

wildbill

Maddel

LINEAWEAVER

Taffy

threedigits

Taffy

ned37

Khristi

bushmechanic

Mazzokie

husabutt

Khristi

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