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Old 12-31-2004, 03:48 PM   #1
gaspipe OP
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Location: Pickwick Lake, Tennessippi
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LC4 Valve Clearance Question.....

Creep and you other LC4 dudes: My '01 640 Adventure calls for valves to be 0.15mm for both intake and exhaust, per the book. For some reason, KTM spec'd 0.10mm for intake and exhaust on my '96 620 RXC, per the book.

I have been setting my 640 at 0.15mm, and my 620 at 0.10mm since I got them.

The 620 has always been a BASTAGE and a half to start when hot. Last night, I decided to check the valves on the 620 since gaspipe wife has deserted me since xmas eve.

The intakes and exhaust were right where I left them, at 0.10mm. I decided to leave the intakes at 0.10mm, and I opened up the exhaust clearance to 0.127mm.

I rode the bike to work today. It starts MUCH easier when hot now.

So the questions:

A) Is there some scientific reason to not just set the 620 valves at 0.15mm like the 640? Slappy valves are happy valves, yes?

B) Was KTM still figuring it all out in '96, or have there been some significant material changes that warrant the different specs?

TIA for any thoughts, and Happy New Year to you thumpers. BTW, the RXC ran so nice, I strapped a case of Kolorado Koolaide to it and rode home tonight. The Hardin County Sheriff laughed his ass off at the state line checkin' for drunks traffic stop.

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Old 12-31-2004, 08:43 PM   #2
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Chances are the difference in spec is in the heat each engine is capable of producing... and dissipating. Also, the valve and seat materials used from year to year.

If it's hard to start when hot, but seems to turn over unusually easy, then yes, chances are the valves are being held open a bit.
Worst case scenario, if this has been an ongoing thing... you may have damaged the exhaust valves... they are unable to shed much heat into the head if they do not fully seat, and can distort and even break.

I don't want to be the barrer of bad news, and thats not the very worst that can happen... just the most likely.

Creep
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Old 12-31-2004, 09:46 PM   #3
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Creep,

Thanks for the insight. Wonder if I'd best set 'em back tight to 0.10mm......IMHO, it runs too well yet, and is too much of a hwore to kick for valve damage, but then again you really never know till the leakdown test and a visual.

Even if it's FUBAR, I like it too much to let it die. This bike has always been a strong one.

Happy New Year to you. 14 minutes to go in Gaspipe land.

'Pipe

Quote:
Originally Posted by creeper
Chances are the difference in spec is in the heat each engine is capable of producing... and dissipating. Also, the valve and seat materials used from year to year.

If it's hard to start when hot, but seems to turn over unusually easy, then yes, chances are the valves are being held open a bit.
Worst case scenario, if this has been an ongoing thing... you may have damaged the exhaust valves... they are unable to shed much heat into the head if they do not fully seat, and can distort and even break.

I don't want to be the barrer of bad news, and thats not the very worst that can happen... just the most likely.

Creep
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Old 01-01-2005, 12:38 AM   #4
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Quote:
Originally Posted by gaspipe
Creep,

Thanks for the insight. Wonder if I'd best set 'em back tight to 0.10mm......IMHO, it runs too well yet, and is too much of a hwore to kick for valve damage, but then again you really never know till the leakdown test and a visual.

Even if it's FUBAR, I like it too much to let it die. This bike has always been a strong one.

Happy New Year to you. 14 minutes to go in Gaspipe land.

'Pipe
I doubt it will hurt them to run the the same spec as a late model LC4. A bit looser is not so much better for noise but shouldn't damage the valve train... at least not as much as too tight.
Should you need head work in the future, and don't mind pulling it off, boxing it up and sending it to Washington, I should be up and running by the first week in February.

Just got back from the big fireworks show by the lake... time for bed.

Chat again in '05.

Creep
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Old 01-01-2005, 01:14 AM   #5
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Have the exhaust clearance tightened up much between adjustments? If not then I would'nt be concerned about and problems due to the 10mm clearance. Actually if it runs well, who cares.
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