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Old 03-31-2010, 12:44 AM   #1
DaBit OP
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LC4Adv clutch engagement moves closer to handlebar at highway speeds.

Original title: 'LC4Adv crankcase ventilation: what's inside the frame tube?'

My KTM LC4 640 Adventure 2003 (55k km/35k miles on the odo) suffers a bit from 'clutch engagement point moving closer to the handlebars after a stretch of highway at 75mph/120kmh/5500rpm'. Other than that it's quite irritating the clutch functions normally.

After replacing the clutch fluid several times and pulling the clutch cover, dismounting and inspecting the clutch I have not yet found a problem. I still have to pull the clutch slave and inspect that, but since it's not leaking (no fluid loss in the container) and performing well as long as I do not run long stretches of highway, I don't think the slave is the problem.

A search here at the forum gave 'crankcase ventilation' as a possible source for this behaviour. Sounds reasonable since the problem only occurs when the engine is loaded, and the clutch problem is not engine temperature related. So when I had the tank off, I decided to check the ventilation.

It seems OK; no kinked hoses, hoses are open. But when trying to blow through the engine connection hoses, I feel some resistance. I'm not sure if it's too much. Hard to describe air resistance in words. I would also expect at least a small amount of condensed oil in the hose running to the air filter box, but there is none.

Two thick ventilation hoses run from engine to the frame tube, a smaller hose leaves the tube and goes to the air filter box.

Now, what's in between?

DaBit screwed with this post 04-02-2010 at 01:00 PM Reason: changed title
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Old 03-31-2010, 03:56 AM   #2
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I sent you a PM.

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Old 03-31-2010, 06:44 AM   #3
Laromonster
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Quote:
Originally Posted by dlh62c
I sent you a PM.

daryl
Send me a PM too, i wanna know as well



promise i wont tell anyone
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Old 03-31-2010, 07:07 AM   #4
DaBit OP
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The PM was about some documentation, but unfortunately it did not contain anything about the innards of the central frame tube.

That's a weird thing with KTM. I have a user manual which describes various tasks, an engine service manual, service manuals for the shock and front forks, but not much about the rest. With my previous motorcycles I had a workshop manual that covered every aspect of the bike.
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Old 03-31-2010, 07:38 AM   #5
robberst
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Hey
I've been wondering about this too. What is in that upper frame tube? I have a '99 with cable actuated clutch and no problems, however on my last oil change/ valve check, there was a glob of back plastic mesh/filter type material getting smashed up in the exhaust valve springs. The crank case vent is the only place it could have gotten in there.
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Old 03-31-2010, 07:42 AM   #6
gunnerbuck
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That gob of goo was the vent tube filter... It must of slid down the tube and dropped into the valve area... It is supposed to reside in the tube near the top frame clamp...
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Old 03-31-2010, 08:02 AM   #7
gunnerbuck
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Quote:
Originally Posted by DaBit
My KTM LC4 640 Adventure 2003 (55k km/35k miles on the odo) suffers a bit from 'clutch engagement point moving closer to the handlebars after a stretch of highway at 75mph/120kmh/5500rpm'. Other than that it's quite irritating the clutch functions normally.

After replacing the clutch fluid several times and pulling the clutch cover, dismounting and inspecting the clutch I have not yet found a problem. I still have to pull the clutch slave and inspect that, but since it's not leaking (no fluid loss in the container) and performing well as long as I do not run long stretches of highway, I don't think the slave is the problem.

A search here at the forum gave 'crankcase ventilation' as a possible source for this behaviour. Sounds reasonable since the problem only occurs when the engine is loaded, and the clutch problem is not engine temperature related. So when I had the tank off, I decided to check the ventilation.

It seems OK; no kinked hoses, hoses are open. But when trying to blow through the engine connection hoses, I feel some resistance. I'm not sure if it's too much. Hard to describe air resistance in words. I would also expect at least a small amount of condensed oil in the hose running to the air filter box, but there is none.

Two thick ventilation hoses run from engine to the frame tube, a smaller hose leaves the tube and goes to the air filter box.

Now, what's in between?
I believe the backbone vent is designed so anything pushed out through the valve cover vent will end up draining back into the engine through the case vent.. If excessive pressure builds through an overfull engine or a faulty piston/top end then too much oil ends up in the backbone tube and the case vent cant keep up so it ends up in the airbox through the higher airbox vent...

It is possible that the higher oil pressure while running at speed will push the clutch slave piston back, giving a bit of slack for the first squeeze or 2 of the clutch lever to pick up.... You could check the vent filter in the valve cover vent tube for partial blockage...

If your clutch slave piston O-ring is faulty the pressure will actually push the mineral oil out of the clutch master weep hole....

gunnerbuck screwed with this post 03-31-2010 at 08:11 AM
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Old 03-31-2010, 08:40 AM   #8
DaBit OP
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Quote:
Originally Posted by robberst
there was a glob of back plastic mesh/filter type material getting smashed up in the exhaust valve springs.
That is a filter which normally resides in the vent hose. I suppose it is used to condense oil vapour so it returns to the engine instead of being blown in the air filter box.

I wonder what the side effect of removing this filter is? I don't like loose things inside hoses, and mine gathered some 'mayonaise' during the winter months. Eventually the 'mayonaise' may clog it up.

Also, in the case vent hose there was not such a filter. Should there be one in that hose?

Quote:
Originally Posted by gunnerbuck
I believe the backbone vent is designed so anything pushed out through the valve cover vent will end up draining back into the engine through the case vent..
It looks that way. That would probably mean that the smaller vent tube leading to the air filter box is just a length of pipe sticking high in the central frame tube?

Quote:
It is possible that the higher oil pressure while running at speed will push the clutch slave piston back, giving a bit of slack for the first squeeze or 2 of the clutch lever to pick up....
I don't have to squeeze twice. It is only that the engagement point moves closer to the handlebars. Often enough to make adjusting the clutch lever necessary. But even when I have to adjust the clutch lever the problem does not get worse over time. The engagement point just shifts, and that's it.

When i stop at a gas station and leave the bike alone for 5 minutes, the clutch is back at it's original engagement point. That's why I wanted to check crankcase ventilation.

Quote:
You could check the vent filter in the valve cover vent tube for partial blockage...
It did gather some mayonaise in the winter... That counts as 'partial blockage' in my book. But the clutch problem is already there as long as I have the bike (since last summer), and the problem is there also in the summer.

Quote:
If your clutch slave piston O-ring is faulty the pressure will actually push the mineral oil out of the clutch master weep hole....
I don't suspect the slave cylinder for now. The symptoms do not point to the slave as the guilty component.
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Old 03-31-2010, 09:11 AM   #9
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O ring on the slave is bad or the walls of the slave have been worn down inside on the coating...

I dont run a spooge sponge.... no issues like soaked oil filter etc
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Old 03-31-2010, 09:16 AM   #10
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I cut apart one of my LC4 frames recently, both down tubes and the oil filter attachment point. If anybody is interested I can take some pictures of the insides next time I am in the garage.

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Old 03-31-2010, 09:54 AM   #11
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Quote:
Originally Posted by LukasM
I cut apart one of my LC4 frames...


Cut apart a good LC4 frame?!?! And one of them, implying you have more just lying around?!?!?



Good, that's something I like to see!

However, aren't we talking about the "backbone" tube, with the red line?




Cheers,

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Old 03-31-2010, 10:58 AM   #12
LukasM
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Tseta,

I didn't cut it apart just for fun, you know! Although I enjoyed it quite a bit.
Had 3 LC4 frames here, one from a Duke and 2 from the 640-Adventures that I parted out. So now I have 2.5 left.


I didn't really read all of the thread, just saw that somebody asked about the insides of the tubes. Unfortunately I don't plan on cutting any more so you'll have to do your own frame if you want to see the upper tube!

Lukas
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Old 04-01-2010, 02:03 AM   #13
DaBit OP
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Quote:
Originally Posted by wrk2surf
O ring on the slave is bad or the walls of the slave have been worn down inside on the coating...
How would that cause the engagement point to shift during a stretch of highway?

Pulling the slave cylinder was a no-brainer, right? I might as well check it out.

I also have a spare engine which contains a slave cylinder. If I decide to swap the cylinders and see what happens, do i really have to adjust the 'Dimension Y' (distance between the sealing surface of slave and the pushrod)? Or is it usually OK to just swap out the slave cylinders?

Quote:
I dont run a spooge sponge.... no issues like soaked oil filter etc
OK then. I will leave it out. I don't like that loose bit in the hose.
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Old 04-01-2010, 02:26 AM   #14
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Hey lukas. any chance of grabbing a left bottom frame rail? i bent mine pretty bad on an 07 640A. do you knom if they would fit?

heres a pic



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Old 04-01-2010, 02:29 AM   #15
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sorry to hijack ya thread DaBit......
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