Just completed a long piste in Mauritania on 2000 640 Adv.

Discovered that all the coolant in the radiator has disappeared, and the oil has the consistency of a chocalate milkshake, hence there must be coolant in the oil. This would suggest to me that the head gasket has blown.

I have spent the morning searching Adv Rider and the net, and I cant find much info on the 640 Adv blowing head gaskets. Everyone who seems to have oil and coolant problems seems to blame it on the water pump.

I am taking it all apart later today, but interested to find out if anyone else has had experience with water pump and / or head gasket failures.

Also; to get to the head gasket I assume I dont have to completemly remove the engine. Is this correct?

cheers

Not much I can do for you but hang in there. A few years ago I helped a swedish guy work on his 640 under the midnight sun at Inuvik. Thats at the end of the northernmost road in canada. He had the water/oil mix going on and ended up hauling the bike to alaska. It would be nice if it was the water pump on yours.

Hi Matt,

Could be either water pump or head gasket as you already mentioned.

Remove the water pump and see if there are any signs of a leak could be the seal has failed. The bearing may have lateral play causing the seal to fail.

Very often with a head gasket failing the water jacket becomes pressurised and the water is blow out of the over flow.

If all the water went into the oil I would reckon the water pump is the most likely cause.

I have a KTM manual hear if you need any info, torque settings etc.

It does not show if the cylinder head can be removed in the frame.

Steve

Head gasket failures are not uncommon on the LC 4 and it has been suggested that the 2 nuts/studs {1 front and 1 back} on the cylinder head should be retensioned after a short period to prevent this...

The head gasket can be changed without removing the engine...

Thanks all for your comments;

Took it apart today. The water pump has failed and the head gasket has blown as well. I checked the piston rings and fortunately they seem ok.

Now I just have to wait to experience the joys of shipping parts to Mauritania!

Steve - just about to send you a PM. If you have a copy of the workshop manual in emailable form, Id really appreciate a copy!

Island Hopper - Good observation re: cylinder head nuts. They were a lot looser than I expected.

cheers

Gents,

A few more questions if you dont mind...........

My parts eventually arrived and I put the cylinder head and a new water pump back on, but I seemed to have made two monumental mistakes somewhere in the process.

I thought I had adjusted the timing chain correctly, but on starting the engine the timing is clearly way out and the bike was running very hot. Does anyone have a simple way to describe how to correctly adjust the timing chain?

Secondly, after changing the oil and the filters and running the engine for less than five minutes, I checked the oil level again. Water has again mixed in with the oil. I took the cylinder head off again and the head gasket seems fine. Because I didnt have a torque wrench I had adjusted all the bolts by hand, and they seemed very firm. Is it possible that if the bolts are not tightened sufficiently, water could leak again? If so, and someone has the correct tensions to hand, would you mind posting them here, as I dont have a workshop manual on the road!

Lastly, although I havent checked it yet, I thought that maybe the base gasket had blown as well - anyone have any experience with this failing as well?

cheers

The timing chain should be adjusted as follows: The engine should be locked at top dead center using a locking bolt. On the left side behind the screw on oil filter you will see a bolt that has a 10mm head... Remove this bolt and roll the engine to TDC .... At TDC you can see the window bubble and the flywheel mark aligned in the right side inspection window.... Now if you shine a flashlight into the locating hole {behind filter} you should see a cutout recess on the crankweb that a locking bolt engages to hold engine at TDC. Now the locking bolt is a KTM special tool but you can fashion one by filing a point on a 8mm thread size bolt..... Or you could wing it and try to hold the engine steady without the locking bolt in place and hope for the best....

Next you want to put the cam sprocket in place under the cam chain. With the chain tensioned at the front of the sprocket, a punch mark on the outer edge of the sprocket should be just visible lining up with the front gasket surface of the head. Adjust {reposition sprocket under chain} until you get it to align.... Next slide the camshaft in place with the punchmark on the inner rim of the sprocket lining up with the index line on the end of the camshaft..... Then verify that all three marks {TDC, outer cam sprocket punchmark to gasket surface and inner camsprocket punchmark to camshaft end index mark} align and you're there.....

Also having the TDC locking bolt in place makes it a lot easier to tension the camsprocket bolt to the required 35N/M {25 FT/LBS} and don't forget to loctite this one.....Also don't forget to slack off the ratchet setting on the camchain tensioner before you reinstall it so the chain is not zinging tight....

You have to be careful not to overtighten the head bolts as well as this could distort the surface and cause leakage.... 50 n/m on the 10mm bolts, I think 25 n/m on the 2 stud nuts and 8 n/m {on pre 03} 10 n/m {on post 03} for the 6mm bolts....

A lean condition from a leaking head gasket could also make your engine run hot {glowing pipes}.

The base gasket isn't a water seal gasket so it wouldn't leak through there.... You have the head gasket, the waterpump or a cracked cylinder/head as points of entry for the water.....

Gotta go, Good luck....
David....

Much appreciated Island Hopper,

I had aligned the timing mark on the inner part of the cam sprocket, but for some reason missed aligning the timing mark on the outer part of the sprocket.

On further investigation, I think the head may actually be slightly warped. I put the cylinder head back on, without the head gasket and was able to slide a 0.1mm feeder guage around between the head and the cylinder block. This seems to me like far too big a gap - does anyone know if there should be any tolerance here - I would have thought that it should not be possible to fit anything through here - if so, I assume the solution would be to file or machine the head slightly?

cheers

if you are going to home grind it get a piece of plate glass and use that with some grinding paste - this will make sure that the mating surface is flat

Hi Matt,

You are entering areas I don't have any KTM experience with. I would say the flatnes on the head would depend on the type of head gasket the KTM uses.

I just checked the KTM manual and the tolerance is 0.1 mm 0.004"

Manual reads........
Sealing area
Check spark plug threads and valve seats for damage or cracks. Check
the sealing area to the cylinder for distortions with a straightedge and a
feeler gauge. Distortion limit 0.10 mm (0.004 in).

Steve

When you remove material from the cylinder head mating surfaces you also increase the compression ratio of the engine. This could be offset by using a thicker base gasket to get things back to spec....

The head gasket is pretty thick on these engines so I would think it could absorb a 0.10 mm intolerance.... It is very important how you tighten the head bolts during reassembly for getting a good seal.... The 4 big bolts should be tightened in a crosswise pattern in several sequences, then the stud nuts front and back and lastly the 2 smallest 6 mm screws.....

I would suggest upon reassembly to put a light coating of gasgacinch {or similar high pressure liquid gasket} on both surfaces {cylinder+head} and see if that cures your leakage....

It may be wise once you have things back together to pressure test the top end cooling system and see if it holds air..... Probably the best way to find a leak.....

Good luck...
David....

Matt,
It has been weeks after meeting you and watching your bike in various stages of dismantling...
You were in Nouackchott waiting for spares to be DHLed, when we had to get back to Holland. Did you get the spares?
So is everything working like it supposed to again
and have you managed to get everything back togehter without having too much pieces missing or leftover? In other words did you manage this crashcourse and go one step further from doing maitenance to being a mechanic?

It was fun meeting you, are your plans changed much now after your delay in Mauritania?

Becarefull and enjoy! (and looking forward to bump into you again sometime/somewhere on the globe...)

BTW it's fun meeting people who regular write here, and you only know by their loginnames, in the flesh.

__________________
bart & sophie

Hi Bart,

Good to hear from you! Are you missing the desert yet?

Would you believe that I am still in Nouakchott with a broken KTM? My original parts delivery arrived, but upon rebuilding the bike I discovered that the piston was cracked, although fortunately the cylinder seems in good condition. Hence another DHL delivery with a new piston and valves. Reassembled the bike in NKT, ran it for a few days and then took off for Mali yesterday.

I made it 100kms down the Route Despoir before a horrible noise came from the electric starter. I trucked it back to NKT, took it apart and discovered that the flywheel now has a very large crack.

I thought this might have been caused by a failure of the starter bearing (Part No 58440026000 - which I have replaced twice before) but this seemed ok. The crankshaft currently turns ok with the kick-starter so it doesnt seem to be a crankshaft problem.

I am currently at a loss to work out what could have caused the flywheel to crack? I can order a new one and wait another few weeks for DHL to ship it out here, but I am rather concerned that I am missing a bigger problem somewhere?

Any thoughts would be much appreciated!

cheers

Hi Matt,

sorry to hear about your continued problems.

I can't offer any advice but if you get completely stuck I came across what appeared to me to be a good KTM workshop in Zagora Morocco. I know you are in Mauritainia but it maybe the nearest.
They were working on a 950 in a very clean workshop. Spares could still be a issue but they know the insides of a 640.

Steve

Hey Matt

Are you trying to beat my NKT endurance record???

__________________
Simon

London-Cape Town 2004-06
Buenos Aires-Vancouver 2008-10:
http://www.horizonsunlimited.com/tstories/fitzpatrick