Valve adjustments.......

OK, before anyone gives me link to the Holeshot forum, I have already looked at it.

I adjusted my valves this evening, and hopefully they are correct. My dealer, no clue. We even popped out the KTM service manual for the shop on the engine. I got 95% of my info from this, and the Holeshot forum.

BUT - as a first timer in 4 strokes, I had some problems, which hopefully you guys can answer, and can help some others in the future.

-When I found TDC, I was able to fit the .004" feeler in it's designated location. After a few minutes, I think I got the guage at a sufficient drag. After both intake valves were complete, I went to do the exhaust. To my surprise, I could not get the .006 feeler in the gap, no matter what. I cranked the engine by hand for one full piston stroke both ways. This was the only way to get the exhaust valves to "unweight". There is no mention anywhere of cranking the engine over 180 degrees to get the exhaust valves to do this "unweighting". Before I start the bike tomorow, I want to see if this IS a correct proceedure. If it's not, wouldn't an exhaust valve adjustment done on the same stroke as the intake valves cause the valving to be 180 degrees off?

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'01 KTM 520 SX

'95 KX 250 FOR SALE!!! -asking $2000 with decent amount of plastics/decals, parts!!

AMA Dist 6 Member

Hare Scramble Class B #523

Just bringing this thing up to the top, I moved it down.... :)

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'01 KTM 520 SX

'95 KX 250 FOR SALE!!! -asking $2000 with decent amount of plastics/decals, parts!!

AMA Dist 6 Member

Hare Scramble Class B #523

If you had to rotate the crank to unweight the ex.valve you did not adjust at TDC.The easy way is to remove the ignition cover. If you look at the flywheel you will see a metal strip welded to the flywheel. This strip lined up with the pickup is appo TDC remove the crank locking bolt and slowly rotate till the notch in the crank shows up in the hole.Your valves could have seated that is why you could not get your feeler guage in there.

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TWIST&SHOUT

In any event though, you're saying I should be able to adjust BOTH intake and exhaust valves with the crank locked in TDC, and NOT have to move it at all to adjust the other set of valves? Which TDC though? Compression stroke, or exhaust stroke? Perhaps that is not a concern, as the crank and ignition will only lock in one position?

The whole proceedure seems very half-@ssed. No "official" booklet on how to do it, and even the shop can't say they have a good idea. No contact numbers to KTM, and just all around, seems to be pretty lame.

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'01 KTM 520 SX

'95 KX 250 FOR SALE!!! -asking $2000 with decent amount of plastics/decals, parts!!

AMA Dist 6 Member

Hare Scramble Class B #523

[This message has been edited by Chris Slade (edited September 25, 2001).]

>In any event though, you're saying I should be able to adjust BOTH intake and exhaust valves with the crank locked in TDC, and NOT have to move it at all to adjust the other set of valves? <

Yes. TDC on compression stroke. Both intake and exhaust at once. If you can't get the feeler in there, it's too tight. Loosen the lock nut, back it out a turn or two, slip the feeler in the gap. Then tighten the adjuster down on the feeler blade. Back it off a whisker, lock the nut. You're done.

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'01 KTM 520 EXC

'95 Suzuki DR350 Dirt

'01 Silverado 2500HD 4x4 Duramax/ZF-6spd

Also, to get them to "unweight," just wiggle on the rocker arm with your fingers.

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'01 KTM 520 EXC

'95 Suzuki DR350 Dirt

'01 Silverado 2500HD 4x4 Duramax/ZF-6spd

Originally posted by Chris Slade:

Perhaps that is not a concern, as the crank and ignition will only lock in one position?

You could still be 360 out if you use the crank locking bolt. It'll be in the same position on the compression or exhaust stroke. You want to watch your intake valves. The TDC you want is just after they close.

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John Brunsgaard

jejb@att.net

01 400 EXC, 99 250 EXC (gone), 99 200 EXC, 98 125 EXC, 98 380 MXC (long gone)

[This message has been edited by jeb (edited September 26, 2001).]

Chris - you definately DO NOT want the exhaust stroke for adjust the clearance on the exhaust valves. Let me see if I can make some sense as to why - just think about the basic operation of a 4-stroke.

Intake (intake valves open)

Compression (Intake and Exhaust closed)

---- Valve adjust here ----

Power (Intake and Exhaust closed)

Exhaust (exhaust open)

Valves are adjusted when they are completely closed and hopefully (if adjusted correctly) there is no pressure from the cam on them. The purpose of clearance is to ensure that when the engine is hot that the valves do in fact close completely (instead of the cam holding them slightly open). Too much clearance = clicking. Too little = low compression and burnt valves as hot gases squeeze by.

On the exhaust stroke the exhaust valves are open and therefore have pressure on them. Actually - at TDC on the exhaust stroke usually the intakes are starting to open as well which is counter to what you mentioned.

At TDC (or anywhere close - my feeling is within +/-20 degrees of crank rototion - but KTM has the lock so I guess might as well use it) on compression stroke both valves should definately be closed (and therefore "unweighted) as this is when the engine goes bang and you want things sealed.

With both valve covers off you should be able to watch and easily determine where you are at (and also realize why you wouldn't have any clearance on the exhaust stroke). If you don't want to take the side cover off - use a straw down the spark plug hole to see when the piston is at the top.

Last thing - the crank locks in one position - but there are TWO crank rotations for every ONE cam rotation. You want the cam to be in the right position. The right crank rotation to be at is the one after the intakes close.

Sorry for the long post - hope this helps.

Mathew

Well, amidst all of this, I took a chance. I fired her up this early afternoon. Took a few kicks, but I wasn't giving it a good kick....just in case...you know, and the fuel was completely gone.

She fires up, with I think slightly les noise than is used to....but still 'cammy'. I won't worry about it.

She seems snappier, which I assume is a good sign.

Here's how I had done it.

1) removed all parts necessary

2) rotated crank until I thought was TDC, and when it seemed intake valves were fully closed. Feeler guage went in ok.

3) Adjusted intakes

4) No go on getting the .006 feeler in the exhaust valves.

5) Remove lock bolt, don't even worry about it.

6) Spin crank until the enhaust valves unweighted, and .06 feeler went in.

7) Adjusted exhaust valves.

8) Put everything back.

9) Kicked over lightly with kill button depressed, listening for any noises.

10) Fire her up.

11) Nothing blows, runs great, assume all is well.

Just a note - the specified TDC should be unimportant, as the cam nubs are not impacting valves at all until just before the valve opens. As long as the cams are not putting pressure on the valves, it doesn't matter if it's TDC or not...as long as the valves are unweighted, it's ok, this isn't a timing adjustment.

Comments?

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'01 KTM 520 SX

'95 KX 250 FOR SALE!!! -asking $2000 with decent amount of plastics/decals, parts!!

AMA Dist 6 Member

Hare Scramble Class B #523

Glad to hear of your success!

I think if you had looked at the intakes during step 6 of your list - they would have been unloaded as well. You were probably on the exhaust stroke during steps 1-4.

I agree mostly with your last statement. However - you do want to make sure you are close to TDC as if you are in the region of the cam where it ramps up to contact with the valve you will be off by whatever the ramp up is. Not sure exactly how far you can be off before the profile starts up on the cam - but I figure +/- 20 degrees or so is quite safe and easy to hit.

Remember gentlemen this bike has a autodecompresson device on the cam which operates on the exhaust valves. When the engine is turning slowly it slightly opens the exhaust valves, when the engine fires it quickly speeds up and centrifigal force pushes the weight outward rotating a small pin to the flat side causing normal exhaust valve train operation.

My point is if you carefully watch the exhaust valves you can see the exhaust valves slightly open when you slowly rotate the engine over and this occures close to TDC on the compression stroke. If your exhaust cam follower is resting on the autodecompression device your exhaust valves will be tight and your intakes loose.

You must be certin you are at exactly TDC on the compression stroke and BOTH valves should be slightly loose.

Another point on the crank locking bolt it has a tapered tip which is to go into a notch cut in the crankshaft locking it at TDC you must make sure its TDC on the Compression stroke. A similar locking bolt is used on Rotax and LC4 motors (although its in a slighly different location). If you look into the locking bolt hole using a flashlight you can see the notch cut to receive the tip of the locking bolt. This is handy on engine disassembly allowing easy removal of nuts on the crank, etc. since it locks the motor crankshaft firmly in place.

I just completed a valve adjustment on my 520 after about 4 hours of running. One intake and both exhausts required minor adjustment.

This is a tough motor to adjust the valves on because of access. I drained the oil and coolant. Removed the top radiator hoses and hung the radiators outboard with bungie cords from the handlbars allowing easy access to the exhaust valve cover area. I also loosened both carb clamps and rotated the carb slighly to the right allowing easier access to the intake valve cover area.

I removed the magneto cover and used the 17mm nut on the end of the flywheel to turn over the engine with the spark plug remeoved. Use of a long NON RIGID shaft (Soda Straw) also helps in locating exact TDC but make sure its on the compression stroke (both valves fully close with slight play at the rocker arms.

Never stick a rigid device in the spark plug hole to help determine TDC as the stroke of the valves will catch on it and either break it (like a wood pencil) or cause engine damage (like a metal screw driver).

Good luck all

Clark

[This message has been edited by Clark Mason (edited September 25, 2001).]

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