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Old 11-01-2010, 03:46 PM   #1
clintnz OP
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Joined: May 2004
Location: Rotoiti, New Zealand
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Clintnz's KTM 640 95,000km service

I was hoping to get to the 100K km mark but it was not to be, the metal on the sump bungs when I went to do a service last night confirmed that I wasn't just being paranoid when I thought the ol 640 was rattling a bit more than usual.



But hey, what's this sitting on the workbench?



Luck would have it that I had just taken delivery of a big batch of parts, cheap from the USA c/- a friend who has just been over there. So I decided to tear into it. Starting a thread to detail the process seemed like a good idea so I can remember how it goes back together & maybe some of the engine & LC4 gurus on here can stop me doing anything stoopid.

I wanted to get the top end off asap so I could check the bore & find out which piston I have (I or II) so I can order the piston kit, the last major item I need (I hope) None in stock in NZ so that will be a 3-4 week wait.

The good news is that the cylinder looks OK. I brought it into work today & the workshop foreman measured it up with an internal micrometer, 101.00 mm everywhere. There is some scuffing but maybe not too bad? None of the marks can really be felt, What say the experts?







I didn't have the camera at home last night so I will get more pics tonight along with some measurements of wear on the parts I have dismantled so far.

Cheers
Clint
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'03 KTM 640 LC4 Enduro

The wilderness, the desert - why are they not crowded
.................................................. .....with pilgrims?

clintnz screwed with this post 11-02-2010 at 02:05 PM
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Old 11-01-2010, 04:08 PM   #2
clintnz OP
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Anybody know anything about cylinder bore surface roughness? I've got a wee gadget that I use at work for measuring roughness so I thought I'd run it over the cylinder while it was sitting on my desk. It would only fit in sideways so the below readings are taken in the direction of piston travel, 1/2 way down the bore:

Back wall (worn area) Ra = 41 micro inches
Cam side wall (non worn area) Ra = 33 micro inches.

I have Rz numbers & metric equivalents too if anyone is interested.

Cheers
Clint
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'03 KTM 640 LC4 Enduro

The wilderness, the desert - why are they not crowded
.................................................. .....with pilgrims?
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Old 11-01-2010, 04:17 PM   #3
gunnerbuck
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I see you have a new con rod kit... Those fine wear lines on the front and back of the cylinder could be an indicator that the old one is starting to go....

A light hone should fix that up...

Did you check the ring end gap,old VS new rings?
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Old 11-01-2010, 04:22 PM   #4
Phreaky Phil
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Old 11-01-2010, 04:48 PM   #5
clintnz OP
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Quote:
Originally Posted by gunnerbuck
I see you have a new con rod kit... Those fine wear lines on the front and back of the cylinder could be an indicator that the old one is starting to go....

A light hone should fix that up...

Did you check the ring end gap,old VS new rings?
Yep, I think there is a good chance that the metal flakes on the magnet are from the big end, there didn't seem to be much radial play just wiggling it but the rod could be rocked side to side a fair bit.

I'm going to measure the end gap & piston wear tonight, the piston & rings certainly looked due for replacement. I'm also going to take apart the rocker assembly, it will be interesting to see how much wear there is on the inlet roller bearing.

Cheers
Clint
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The wilderness, the desert - why are they not crowded
.................................................. .....with pilgrims?
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Old 11-02-2010, 12:00 AM   #6
Tseta
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We are getting many great rebuild threads here this winter!



Quote:
Originally Posted by clintnz
Yep, I think there is a good chance that the metal flakes on the magnet are from the big end, there didn't seem to be much radial play just wiggling it but the rod could be rocked side to side a fair bit.


In the '98 engine I'm doing, the rod does move side to side surprisingly much. However, the specification for axial play is as great as 1.0mm. Try it with a feeler gauge, it probably is within spec. The radial play is a different animal, I have no idea how to measure that.

Cheers,

Tseta
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Old 11-02-2010, 12:55 AM   #7
benno.h
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Quote:
Originally Posted by gunnerbuck
I see you have a new con rod kit... Those fine wear lines on the front and back of the cylinder could be an indicator that the old one is starting to go....

A light hone should fix that up...

Did you check the ring end gap,old VS new rings?
Hey mate,
could you elaborate on this rod issue?

I've been having some issues with my XR and the machinist reckons the rod may be at fault.
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Old 11-02-2010, 01:25 AM   #8
Mark_S
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hope you get this all buttoned up before the Burt

will be watching with interest
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Old 11-02-2010, 11:01 AM   #9
gunnerbuck
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Quote:
Originally Posted by benno.h
Hey mate,
could you elaborate on this rod issue?

I've been having some issues with my XR and the machinist reckons the rod may be at fault.
I have taken small engines apart with failed con rods and they often display piston cylinder scoring... I can only guess as to what exactly takes place to cause this but I would think that the vertical slop in the shot rod bearing causes the piston to rock back and forth at a much more accelerated rate than normal....
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Old 11-02-2010, 12:51 PM   #10
Rosie!
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Quote:
Originally Posted by Mark_S
hope you get this all buttoned up before the Burt

will be watching with interest
Sadly the 640 won't be going to the burt
He's had to revert to plan six-hundred-and-ninety
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Old 11-02-2010, 01:23 PM   #11
JensEskildsen
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Looking forward to you're progress.

How is the servicehistory for the bike looking? Any "major" work done previously?
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Old 11-02-2010, 01:47 PM   #12
clintnz OP
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Quote:
Originally Posted by JensEskildsen
Looking forward to you're progress.

How is the servicehistory for the bike looking? Any "major" work done previously?
Hi Jens, you are right, I should give some history of the bike. I bought the 640 new in April 2004, it was a run out 2003. It has been serviced to the recommended schedule from new, by the local KTM dealer for the first 12 months & then by me since then. On the rest of the bike I have had the forks & shock serviced a couple of times each, replaced all the wheel bearings a few times & done the steering head & rear linkage bearings once or twice. I have welded up a crack in & reinforced the rear subframe last year.

I have done the common minor jobs on the motor over the years; re sealed the cam cover, replaced the countershaft seal & o-ring a couple of times & replaced the starter sprag clutch. At 50 000km I replaced all the cam & rocker bearings, rebuilt the water pump & replaced the cam chain. The only part showing excessive wear at that point was the inlet cam follower roller bearing.

Cheers
Clint
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'03 KTM 640 LC4 Enduro

The wilderness, the desert - why are they not crowded
.................................................. .....with pilgrims?
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Old 11-02-2010, 03:07 PM   #13
clintnz OP
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Quote:
Originally Posted by Tseta
We are getting many great rebuild threads here this winter!



In the '98 engine I'm doing, the rod does move side to side surprisingly much. However, the specification for axial play is as great as 1.0mm. Try it with a feeler gauge, it probably is within spec. The radial play is a different animal, I have no idea how to measure that.

Cheers,

Tseta
Trouble is, it's the start of summer here Luckily I have plan #690 in place for the next ride.

The play in the conrod I was referring to is the movement of the top of the rod through an arc side to side.

Anyway, back to the used 640 internal engine parts porn:

Some carbon on the piston, but not too much:



The skirts are well worn, but not too deeply:





The most worn part of the piston skirt measured up with my cheap but fairly accurate calipers at 100.80mm. With the bore at 101.00 this gives a clearance of 0.20mm vs the max spec in the manual of 0.12mm.

The end gap on the top ring was 1.04 & the mid ring was 0.64mm vs the max spec of 0.80mm. The oil ring was 1.25mm vs a max spec of 1.00mm, so well due for replacement.

It's worth noting that despite this wear the bike was not using much oil, maybe 2x 100-200ml top ups between 5000km services.

I pressed out the cam follower rollers & they were in fairly good shape, especially compared with the wear I found on the old inlet roller shaft back when I replaced these at the 50 000km mark.



Then I stripped some more parts off the bike & gave everything a wash.





Cheers
Clint
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'03 KTM 640 LC4 Enduro

The wilderness, the desert - why are they not crowded
.................................................. .....with pilgrims?
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Old 11-02-2010, 03:19 PM   #14
B-Rod
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Just pulled my rocker cover today, and at 30K, my rollers look pretty good. I can't recall, did yours fail at 50,000? I've read a couple posts where they failed at 30K, so I'm doing mine once the parts come in. Bummer about doing this at the beginning of the season. Must be only spring though, so you should be able to enjoy a fresh bike for the majority of the season.

What con-rod kit and piston did you end up with? KTM or other?

Quote:
Originally Posted by clintnz
I pressed out the cam follower rollers & they were in fairly good shape, especially compared with the wear I found on the old inlet roller shaft back when I replaced these at the 50 000km mark.


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Old 11-02-2010, 04:01 PM   #15
Jan from Finland
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Quote:
Originally Posted by clintnz
I was hoping to get to the 100K km mark but it was not to be, the metal on the sump bungs when I went to do a service last night confirmed that I wasn't just being paranoid when I thought the ol 640 was rattling a bit more than usual.

I wouldn't have worried about that amount of metal. Assuming there are no big pieces of bearing casing or such. I have about the same mileage and the engine has been opened twice. Most likely the metal comes from transmission gears. Especially 4th and 5th gears do wear, if you ride too much at low revs.

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