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Old 12-21-2009, 01:41 AM   #1
warewolf OP
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Joined: Oct 2004
Location: Nelson, New Zealand
Oddometer: 2,435
Fixing the 640 base gasket, and more...

My 640 Adventure developed an oil leak at the cylinder base gasket. What began as a small weep became a gusher rather suddenly, prompting a tear-down and replacement by yours truly. As with many service tasks, I looked on here first! but didn’t find any threads detailing the whole process. Rather, there is a whole heap of related posts that helped. So here they are, collected in one spot, along with my notes, observations, gotchas and anything else that I found and thought might be useful if you are attempting this yourself.

Note; this is not a “How To” in the style of creeper, laramie LC4, et al; but rather a collection of information that a home mechanic like me might find useful. However you will find reference to several of their good works herein, thank you gentlemen!

The bike is a 2005 640 Adventure, EU/AU model with 37,000km; bought new by me and always serviced by the book. It has been used for everything from short-distance daily commuting, to multi-day adventure touring, extended road rides including several Grand Challenges (1000 miles in 24 hours), and trail rides with the local off-road club.

During the process, I thought fcuk it, I may as well do a couple of other little jobs:
  • remove the EPC
  • remove the SAS
  • clean the carb and replace the needle jet
  • overhaul the water pump
  • replace the rooted starter clutch and hubs.
Then my professional mechanic friend started throwing further jobs at me:
  • clean the piston crown
  • definitely replace the valve stem seals
  • tidy up the valve seats.
Bugger... so much for putting it together tonight! So this job went well beyond a simple base gasket replacement to almost the full refresh normally done at 50-60,000km.

For quick reference, here are all the other threads – my notes follow:
Aaarrrrgggg!!! damn base gaskets....
Re-sealing the KTM LC4 Rocker Cover
LC4 Engine Removal/Replacement
The BST-40 Bible
EPC (Electronic Power Control) design and deactivation.
KTM LC4 Mikuni BST40 "Venting"... Or, I got bored again.
SAS removal outside the USofA
Rebuilding the LC4 Mechanical Water Pump - a Guide

Guide to changing the oil on an LC4

and for a similar thread, with more information, see:
makazica's LC4 Adv top end fun&games

Contents of this thread:
Preparation
Disassembly
Assembly
Crankshaft Locking Bolt
Removing the SAS (Secondary Air System)
Removing the EPC (Electronic Power Control)
Cleaning the Carb
Water Pump Overhaul
Assembly, continued
And now, firing up...

The KTM repair manual was also consulted regularly.

Stay tuned to this channel...
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Colin
KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-21-2009, 01:41 AM   #2
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Preparation

Initial preparation included reading the manual and various threads here to see a) if I could do it myself, and b) what was needed. First, and most obvious, was Aaarrrrgggg!!! damn base gaskets.... by laramie LC4. I've added to that thread, here. I had no issues with parts: the superseded part fit my later bike perfectly.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-21-2009, 01:43 AM   #3
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Disassembly

I used creeper's excellent Re-sealing the KTM LC4 Rocker Cover to get as far as removing the cam cover. I've done this job twice before, as I sealed the cam cover leak only a few thousand kays before replacing the cam follower bearings.

After removing the water pump, it was time to set the engine at TDC-C. This procedure is used in the KTM repair manual, I'm not sure that it is necessary on disassembly but sure is important on reassembly to set the valve timing. Plus, this being my first time, I wanted to see how it was set before disrupting a known-good engine. And that's when the fun started!

First problem: I tried using a normal bolt in the crankshaft locking hole at the front of the engine. I could not find a specific locking position, and couldn't see anything by looking in the bolt hole. However I did manage to restrict the engine to a few degrees of movement near TDC... this was wrong (and subsequently resolved, as I'll explain later) but it gave me a reference point for now.

Second problem: the KTM repair manual shows the camshaft gear with a positioning dot marked near the chain, which should be aligned with the gasket surface of the head. No such dot was visible on mine!!! I happened to have a mate's LC4 400 in bits in the shed at the time, it had the dot.


So... I took a couple of photos with the engine rotated at each end of the few degrees of movement permitted by my pseudo-locking bolt, and scratched a mark in the cam gear level with the head at the point I thought was TDC. At least this meant I could assemble it back to the same way that it was originally, correctly timed, even if I couldn't use the official marks. Now it was okay to remove the cam chain tensioner (should have checked how far the plunger was extended as an indication of chain wear, but forgot), cam shaft, and cam gear.

And what did I find on removal of the gear? There's the dot, hidden under the cam chain! Further reading of the KTM manual shows the disassembly pictures have the dot visible with the chain in place, but the assembly pictures show the chain held clear of the teeth to expose the dot. Aaarrgghh. I did see another thread with some photos of the cam gear with the dots visible, lost it now. I will edit later if I find it.

It's fairly straightforward from here to remove the exhaust (although I still can't remove the header/mid pipe from the frame with the shock and mud flap in place ) then remove the carb following laramie LC4's LC4 Engine Removel/Replacement.

Next off is the cylinder head: undo the cam chain guide bolt from the left side, the two M6 screws from the left side, the M8 nuts front & rear, then the 4x M10 bolts (2x internal near the cam chain, 2x external near the spark plug). Finally the cylinder base nuts (4x) can be undone and the cylinder removed.

The paper base gasket was split along the LHS at the cam chain tunnel (circled below). It was removed and all traces carefully scraped/cleaned off.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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warewolf screwed with this post 12-21-2009 at 07:39 PM
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Old 12-21-2009, 01:45 AM   #4
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Assembly

Next I was ready to re-install the base gasket and cylinder. The KTM manual says to put some sealant around the cam chain tunnel area, where the original paper gasket leaked. Now at this point, I couldn't find a piston ring compressor, did some further reading, consulted my mechanic friend, and decided to have the dealer fit the cylinder and tend to the valves. Since I don't have a torque wrench that will fit the cylinder base nuts, and I read quite a few comments about people munting the fancy lower oil control piston ring, I figured it was safer and easier to get my dealer to do that step. Ditto attending to the valves, I couldn't even remove them with the tools to hand. So the KTM shop de-glazed and fitted the cylinder, declared the piston worn but serviceable, and attended to the head: de-carbed, re-faced the valves, cut the seats, and replaced the stem seals.

Photos of piston crown, looking a bit oily but okay:


The piston was cleaned, here shown with the cylinder and head gasket in place:


Note the inlet side of the gasket has quite small holes compared to the coolant passage. Is this some ploy to reduce the coolant flow on that side, in order to balance the temperature versus the exhaust?


Photos of the head before/after:




Now, about that crankshaft locking bolt...
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-21-2009, 02:29 AM   #5
warewolf OP
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Crankshaft locking bolt

I tried to use a plain bolt for this, with no luck. I couldn't feel a definite locking point, nor see one through the bolt hole. Using a spare M8 bolt, I filed a few threads off the end to reduce the diameter, mimicking the KTM part, but this didn't help, possibly because it was still too wide. Once the cylinder was removed, all became clear. The crank web is shaped like this:

Note the small notch: that is the TDC point. I'd managed to get the bolt caught in the large cut-out above it, so don't do this!!


Again my mechanic friend stepped in to advise, and upon investigation we spotted the notch. The next day he turns up with an M8 bolt he'd turned down on the lathe to have a conical point:

He suggests the tapered profile helps to ensure you are in the correct notch, as the crank movement will progressively reduce as the bolt is screwed in further. In the wrong place, this won't happen, such as when the bolt simply hits the crank web rather than the notch. And I can tell you, the bolt can easily hit the crank web and stop it turning without being in the notch.

Anyone with a gen-u-wine KTM lock bolt care to elaborate on its dimensions?
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-21-2009, 02:54 AM   #6
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Removing the SAS (Secondary Air System)

This heavy little gem (440g) does little to reduce emissions and has no effect of performance. However it does produce the ‘popping’ sound on the overrun which can add to the noise, especially when amplified by a, umm, ‘free flowing’ exhaust system. One of its main functions is simply to dilute the nasties in the exhaust system by injecting fresh air, thereby reducing the measured parts-per-million at the tail pipe. So it’s gone.

I don’t like half-done jobs, so rather than leave the SAS pipe in place and plug the end somehow; I spent the few dollars extra to buy the SAS Bore Plug, copper sealing washer, and replaced the exhaust header gaskets. Not having access to an engineering workshop with lots of scrap, I’d probably spend more time and money finding & buying the right-sized thing to plug it, than I did getting the proper part from my dealer... at less than the price of a pint of good beer!

I followed Sylvia’s tips in SAS removal outside the USofA. My additions here.

Edits:

btw With the head in situ, the frame makes access to the inner exhaust flange screws awkward, if not impossible in the case of my torque wrench. I didn't 'cos I was impatient (would rather give the cam cover 72 hours to cure), but it would have been better to do it while the head was off.

Initially, my test rides highlighted a marked reduction in the popping. It is still there, just nowhere near as bad.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-21-2009, 12:35 PM   #7
clintnz
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Oooh shiny!

Where did you find the best price on the parts & what did they charge for that head work?

Quote:
Originally Posted by warewolf
Now it was okay to remove the cam chain tensioner (should have checked how far the plunger was extended as an indication of chain wear, but forgot)
If you have a close look at the teeth on the tensioner you will probably be able to see wear where the pawl has been sitting.

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Old 12-21-2009, 02:14 PM   #8
warewolf OP
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I didn't hunt around for parts prices - I have a 'relationship' with my local KTM shop. I buy all my commodity items like bearings, seals etc from my engineering supplies friend by preference, resorting to the KTM fellahs if he can't get it.

btw I did score a pack of 6x10x1 copper washers, 25x for $12.53 from the Champion catalogue. That was the only size he could supply, not counting the ones that I already had from the oil filter kit. But the 6x10x1 are used by the valve inspection covers and is probably the most common size on the bike.

The valves were re-faced as outwork, itemised as $140. The stem seals were $45 for 4x, but I don't know how much of the 2.75 hours 'technician fee' was the valve work, they also attended to the cylinder in that time. Head gasket was $60.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-21-2009, 03:56 PM   #9
clintnz
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Cheers, good to know.

I was in at the local shop today ordering some bits, I asked them what maintenance I should be thinking about doing on a 80k km LC4 motor - their reply: "Oooo, uh, yeah, um I don't think we've actually ever seen one that has done anywhere near those kms..."

They did spot a valve kit for the LC4 in their catalogue, IIRC it had all the valves, springs, collets (maybe not the guides?), seals etc for $400-something, I might plan on getting one of them in. I ordered some new cam follower roller bearings to keep in stock for a future rebuild/just in case
.
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Old 12-21-2009, 07:27 PM   #10
laramie LC4
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very nice. keep it up!

laramie
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Old 12-21-2009, 08:36 PM   #11
bmwktmbill
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What jetting

Warewolf,
Quite a bit of carbon, what jetting are you running on your '05, what airbox, air filter arrangement? What exhaust?
bill
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The faster it goes the faster it breaks.
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Old 12-21-2009, 10:07 PM   #12
warewolf OP
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All stock, Bill.

Completely outta-da-box standard Euro II compliant. MJ:152.5, PJ:45, PAJ:1.2, Needle clip 3. Airbox has the closed sidecover & snorkel fitted. OEM air filter these days runs a filter skin as a crud catcher. Unmodified OEM exhaust. SAS & EPC. Until now... Next project is to uncork it, but once this tidy-up is completed I want to run it for a bit to get a base line with a good needle jet and the SAS/EPC removed.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-22-2009, 01:40 AM   #13
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Removing the EPC (Electronic Power Control)

This item definitely reduces performance so itís gone. Helpful threads included creeperís EPC (Electronic Power Control) design and deactivation and KTM LC4 Mikuni BST40 "Venting"... Or, I got bored again., this latter to answer the question: should I use the OEM filter, or go something better? For the moment I'll run with OEM as the carb is relatively clean.

Not much to add. After I disconnected the wires from the gearbox switches, I cut them off near the connector to the wiring loom, removed the wires and put a little heat-shrink tubing over the exposed ends to keep them clean.

I sourced a plug for the carb top at a rubber supplies place, < $1 for a chair leg stopper diameter 9.5mm, nice and firm on the 10mm connection. Plus I will use the wire clip (belt and suspenders) even though the new stopper is much firmer than the EPC connection ever was.

All the bits I removed weighed 200g. That's gotta make it easier to loft the front in 2nd/3rd gear, eh?
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-22-2009, 01:59 AM   #14
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Cleaning the carb

The bike was running a bit rich, with a sooty tail pipe and not much choke needed to start, even on frosty mornings. My guess was that perennial BST blight: a worn needle jet. Of course, how could you check/clean a BST-40 without laramie LC4ís The BST-40 Bible? The needle jet was worn, visible to a practised eye. Replacement is covered in the disassembly/assembly process in Da Bible.

Two points to note: bmwktmbillís float checking technique is brilliant and oh-so-simple. Attach a length of fuel hose to the inlet, gently blow, move the float to see where the flow stops. With my carb, it was still spot-on, but if I hadnít used this method, I would have got it wrong. You see, the point where the float valve appeared closed was where it started to close. Billís method found where it actually closed, some mm different in float height.

As an afterthought now I'm typing this up, could that misread of the float level explain why some people have bogging issues with the BST? If I'd adjusted the float level per the visual method, it would have made the float chamber rich... which causes the bogging, init?

Second point, or rather a suggestion: later I read in an old magazine a useful technique for removing carb throttle cables is to simply unbolt the anchor plate from the side of the carb. This is quick, easy, and doesnít disturb the slack adjustment of the cables. Nice idea, but on the LC4 one of the screws is obscured by the frame rails. It might be possible to get a right-angled screwdriver in there... or do it after lifting the carb above the frame rails, or even tilting the carb in situ.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 12-22-2009, 02:46 AM   #15
innathyzit
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Quote:
Originally Posted by warewolf

Note the inlet side of the gasket has quite small holes compared to the coolant passage. Is this some ploy to reduce the coolant flow on that side, in order to balance the temperature versus the exhaust?

That is very very common in auto engines as well, actually pretty standard really. Not too sure why , it could be a flow/heat transfer thing like you say, but they also use the gasket to restict the flow instead of casting the holes different to keep the tension more even on the head gaskets bore binder ring. may also have something to do with clearing all the sand and crap out of the water jacket after casting.
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