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auto decompressor on a 630?

mjskier

mjskier

Husqvarna
AA Class
Does the TE 630 have an auto decompressor to help with starting?

My (new to me) '11 didn't start after a few days at home, hardly moving the motor.
I thought the battery was toast (me dropping a wrench across the 2 terminals probably didn't help!)
So I just installed a new EarthX 18C, same deal.
Then I jump started it with my car, kind of the same, but after a few short starter button press the bike finally started. The bike runs beautifully after that.

So I'm starting to think there is an issue with the auto decompressor (if there is one)
But I can't find anything obvious in the shop manual.
What would it be called if indeed there is one?

After I shut it off for a few minutes, the bike did start without the need to jump start. It still strains a bit though.
 
Well, I can somewhat answer my own question.
There is indeed an auto decompressor mechanism, which I kind of understand.
It relies on an additional cam (they call it a "valve lifter" on the part fiche) that can wobble on the camshaft. It is held off-vertical by a fairly weak spring. It is also wider at one end than the other.
I assume that the centrifugal force makes this valve want to align vertically (due to a higher weight on one end) and when the shaft turns fast enough it overcomes the weak spring.

When that cam is off vertical, it keeps the right exhaust valve open.
I can see the mechanism failing when I rotate the camshaft: That cam is pretty narrow, and it only rides on a small side of the rocker lever. Either the cam is worn down, or the rocker is.
I'll figure which one this weekend: Looking at the part fiche, the 4 rockers are all identical. So I'll just swap the 2 exhaust rockers and see if that fixes things.
That's the ideal, cheap solution. If it doesn't work, then I need to get a new valve lifter.

I've got to say, I'm not that impressed with the mechanism.
 
Never had an issue out of mine in 15k miles, it doesn't take much valve lift at all to work...
Have you checked all of the major electrical connections between battery, solenoid and starter? A weak connection could have similar symptoms. Or the starter could be going out.
 
I'm pretty sure it is the auto-decompressor. I can see it sliding off and the valve snapping back in place when rotating with the rear wheel.
And if I take the spark plug out, the starter rotates the engine as expected.
Seeing how that thing works, it wouldn't take much to fail: A rocker or lifter a bit worn off, or machined just a bit wrong.
I'll try to take a video of it failing tonight. It seems pretty obvious to me, but I've been wrong before :)
 
Ok, here it is. You can notice that at the cam lobe heel, (the opposite of the valve lifting part) the lifter gets off track and the valve snaps shut when it should have been open.
At least, that's my interpretation of it. Thoughts?
I did several rotations, but I hat a hard time keeping a smooth motion. 0:42 into the video is probably the best view.

View: https://www.youtube.com/watch?v=tAW4N-p7K6M

 
You may be on the right track here but you're also in uncharted waters, I don't recall anybody else encountering this problem. You might try to watch what happens cranking briefly with the starter and the valve cover off (plug removed). How many miles on the bike?

.
 
I can tell you that Halls has the individual components for the auto decom or can obtain them.

Friend had a problem with his and was able to get the parts. Had nothing to do with replacing the cam or rocker.

If I'm not mistaken, the parts or something about the install required an item to be pressed on the cam shaft.. maybe bearing on the outside of the auto decomp which is housed under the camshaft cap?

I'm taking this from memory of a problem that took place over 2 years ago. Bike would not start due to the auto decomp not working
and the battery would barely turn the motor over. If fact we could hardly even bump start it by pulling the bike.

Halls has the parts diagram on line.
 
There is a point in the rotation, specifically tdc, where the autodecomp is not engaged even with engine not running. I just found this out when checking my valves. At first I just pointed the cam lobes away from the valve, but noticed the valve on which the decomp lever acts was way out of spec (because the valve was part open, lol). Rotated to line up the timing marks per the manual and all was good with the spec check. Just thought this might be relevant.
 
Looks like I'm not the first one to run into this issue. Maybe uncommon on the 630 but this guy ran into the same problem on an 07 TE 450. The mechanism looks the same.

Entry 12 in this thread. My valve lifter looks like it is notched like the one in the picture.
http://www.thumpertalk.com/topic/774689-auto-decompression/

When you look at it, there isn't that much surface between the valve lifter and the rocker lever to make this mechanism work.
So any defect or wear on either surface would make it very easy for the lifter to slide off like mine does.

So I was going to just swap rocker levers to see if it helps. But Halls did have the parts in stock. So for peace of mind I'm going to fix it right. It would really suck to have this fails in the middle of nowhere.

My bike has 6,600 miles. Valves are in spec. Previous owner did mention they had to adjust at 6k.
Good to know it is pretty uncommon.

Here's the pic from the TE 450 in the post I referred to. The shiny surface is what rides on the side of the rocker lever. The screwdriver is holding the valve lifter in the position where it would have no effect on the valve.

20k535u.jpg
 
The TE450 mechanically operated decom release is situated on the handle bar where the 630 fast start mechanism is. That is how my TE510 operated.
 
Fast1 said:
The TE450 mechanically operated decom release is situated on the handle bar where the 630 fast start mechanism is. That is how my TE510 operated.
Click to expand...


The funny thing is that the cable holder is still there on the 630 head (the part that would hold the cable adjuster at the top of the TE 450 pic I posted) I wonder how hard it would be to retrofit a manual decompression if one needed too.

I ended up getting part 14 ($63.50), 17, 16, 15 from page 28 (17, 16, 15 are pennies so not worth second guessing)
as well as part 14 on page 16 (1 rocket arm, $23.99)

So about $100 total after S/H
 
If I recall correctly that is exactly what my friend purchased for his and it solved the problem his 630 had. His was only a few months old when
the problem occurred. I too noticed the valve cover head cable holder. In fact during the first few attempts starting my new 630 I had thought the fast idle was the auto decomp like my TE510 had.

Hope the parts solve the problem for you. I know that a press was required to install them but honestly am not 100% sure if it was for the cam shaft bearing removal and re-install or something else. He did all the work but I was aware of the problem.
 
I might have found what caused the problem in the fist place:
On this video you can see that with the way the rocker arm spring spacer was installed, all the play was on the the rocker used by the auto decompression. The other rocker had no side play whatsoever.

View: http://youtu.be/U7pLPmCtCPU


So I think whoever did the valves last, installed the spring spacer too close to the left rocker, which allowed the right rocker to move inward, which caused the valve lifter to ride half way on the rocker, which caused the rocker to look like this. Yuck!!!

CAM00033-L.jpg
 
Could be. I do notice ur decompressor cam looked a lot more work than mine. My spring retainers move really easy on the shaft. Easy enough that they kinda just flop around side to side and rotate, enough that they wouldn't stay where I put them in a running engine. You'rs pretty tight?
 
The retainer on the exhaust is pretty tight. It doesn't move side to side at all. I didn't check the intake one.
Is that retainer the right length or is it too short by about 1mm?
 
Mines apart now. It's got a little side to side play, maybe .5 mm at most. Let me know if you need pics of anything to compare.
 
bushwa said:
Mines apart now. It's got a little side to side play, maybe .5 mm at most. Let me know if you need pics of anything to compare.
Click to expand...

If you get a chance, please measure the length of your retainer so I can compare to mine.
 
Success!
I put it back together this weekend, crossed my fingers and hit the button. Starter revs the way it should, bike starts, the 2 in 1 FMF powercore with quiet insert sounds good, life is good.
That lifter valve assembly is pretty tricky, The wrong washer thickness and things bind. (Notice on the part list there are 2 washers: parts 9 and 10 page 28.
0.8mm and 1.0mm) You are just supposed to use the correct thickness. Mine was 1.2mm (according to my high precision Harbor Freight special caliper :rolleyes:) I just ran it on 1000 grit sandpaper until it was about 0.9 before things didn't bind anymore.
 
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