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Discussion Starter #1
Got the air box sorted out.....I see that 98 ST2's can have alternator issues...I pulled off the left engine cover to have a look and fix an oil leak...The previous owner had this cover off for some reason...The rotor and stator look small, only 20MM width...But it all appears good.. 3 ohms between the yellow wires,no short to the laminations and no indication of overheating..I was told to see if it was updated with an oil slinger...I see nothing but fins on the rotor...

And the front head is seeping oil from the head gasket area. Leaks enough so I want to fix it....I assume these engines do have head gaskets? Any thing to look for other replacing what leaks? I drained the coolant, it was clean, the radiator and hoses are removed and the timing belt and exhaust are off...And I can check the valves while the head is off..............
 

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the st2 alt rotor was meant to have stronger magnets in it, so it was the same width as the narrow 400/600/750/851 and 888sp one. it was the most powerful single phase alt as listed from memory.

the recall was to replace the spacer behind it (to make up for the narrow rotor on the long nose wide alt crank it shared with the 900ss and m900) with one that had a groove in it to allow oil to flow out from the hole in the centre of the crank that also fed oil into the starter clutch assembly. the replacement rotor looked identical afaicr.

no head gasket, just a metal - metal face join. the head warps, and allows oil to come out of the chamber. pull the head and cylinder and get them machined flat.

get the guides k-lined and valves seated while the head is off.
 

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Discussion Starter #3
Ok...the ST2 head appears to have the recess that seals against the cylinder liner like the air cooled engines...? Any milling will change the "crush" between the head and liner...so it's not a simple milling operation...Or am I looking at this wrong..........? I'll have the head off today and see what actually goes on here..Thanks
 

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Just lap the head with lapping compound until flat, yes it will take a bit but it will fix the problem ... for a while. All water cooled 2-valve motors do this and if you increase the bore and/or make more power it does it sooner. Most do no more than weep a little so owners tend to keep them clean and NOT fix them. It should not be a safety issue as long as the weep is cleaned about every oil change.

Side cover should have at least been removed for the update Belter mentioned, after that there are many reasons .
 

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Discussion Starter #5 (Edited)
The head is off...no signs of oil passing by the head/barrel joint...But look at the photo, you can see the trail of grease and dirt in the 5 o'clock position from a core plug.The core plug is in a coolant passage so it must be a glycol mess..Easy fix I guess...One crankcase stud nut refused to loosen despite using the acetylene/ oxy torch..I spent half an hour with a small chisel splitting the nut...No damage to the stud...Still see honing marks in the cylinder, no wear ridge at all speedo shows 35K miles .Apparently no cylinder liner? Nikasil on the aluminum? It's not magnetic.....I'll check the valve guides while the head is off...

 

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you don't have to believe us if you don't want to.

at the bottom of the photo you can see the finish of the mating surface has a flat appearance, which is where the surfaces have been "working" if you like.

the core plug will have coolant behind it.
 

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Discussion Starter #7
you don't have to believe us if you don't want to.

at the bottom of the photo you can see the finish of the mating surface has a flat appearance, which is where the surfaces have been "working" if you like.

the core plug will have coolant behind it.
Oh, I see it but I don't want to see it.I mentioned it was a coolant plug, but I didn't want to see that either....:nerd: So you want me to put lapping compound on the raised lip of the cylinder and rotate it back and forth on the head until there's an even matte finish all the way around...OK I can do that ..
 

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that's what eric must do, never done it that way myself. hopefully eric will clarify his technique as i'm interested too.

if you get them machined you do both faces and the cylinder as well to keep o-ring loading the same, etc.
 

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Would it not be a good idea to spray some copper coat on the sealing surfaces? It might help heat transfer and stop warping also stopping the slow weep.
 

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Discussion Starter #11
Most of my bike experience is with vintage Triumphs, I have two land speed racers and one holds several records..The heads never warp on those old turds unless there's mistakes in assembly...
I wonder what actually makes the Ducati heads warp in the first place...It's robust looking piece of metal,crankcase studs are the preferred way of securing cylinders and heads...
I mentioned having a problem loosening the top left side cylinder nut, it was seized to the stud..I put pressure on the wrench, the nut and stud wiggled a bit like it was not all that tight..I wonder if the studs stretch over time and might need occasional tightening ? I checked the rear cylinder nut, all four are seized..They are rusty...No where else on the bike is any signs of corrosion, it's a clean bike..
I bet a machine shop would charge at least $500 to jig the head and mill two circular surfaces and the top of the cylinder..
Anyways, the valve clearances are good, no excessive play in the guides and the valve seating looks like it should..I'll do the lapping and see what happens..
 

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Discussion Starter #12 (Edited)
So i pulled the cylinder...cleaned up the parts, pulled out the head dowel, and then put lapping compound on the head and place it over the cylinder. I was able to rotate the head about 20 degrees back and forth.. Did it carefully for about two minutes....Both the the head and top of the cylinder had an even matte finish. I put the head cam side down and placed the cylinder on top....Poured in a water-detergent mix... No leaks at all.......
Of course once it's on the engine torqued down, who knows, but this seems good...
I didn't take off much material,lapping is slow, maybe .001-.002 at best....I'm beginning to believe this leak from at least in part from improperly torqued head nuts...Thanks for the advice !
 

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only the water cooled 2v head does this, and i want to say the 2001 on heads are better - i'm sure there's a visual difference to the casting above the exhaust port. it's not because of any incorrect assembly, it's just what happened.

the nuts on the studs usually get very crappy in their finish over time. maybe its the heat. they can be quite firm to break away, and usually give with a bit of noise.

i'd use brake clean/metho/acetone to see if it leaks. or blue one side and see how much transfer you get.
 

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I'll toss my 2c in here. My 1998 ST2 ran well for the bulk of the 50,000 mi I put on it. (Sold it at about 53K). But, I did have issues with the temp. senders. There are 2. the H sender (usually) goes to the readout. The V sender feeds the ECU. They're Jaeger brand -- French. And they suck. I always thought that the readout seemed low, and then it went intermittent at times. Thought it was the connector on the sender. Never quite nailed it down until the V sender started acting up on a 2500 mile trip. Rough running. I started playing with resistors in place of the sender. 220 Ohm = 207 F on the readout. One warmed up, she ran excellent on the 220 Ohm resistor. Of course, you'll never get the fan to turn on in heavy traffic, but I did all my riding out on back roads.

So I ended up buying Bosch replacements. Did the H one first. When I rode it to work, I left it on the center stand running, until the fan came on. Wow, I saw the readout get to 248F and flash on-and-off. This told me that these OEM senders can drift that far out and lie to you. BTW the fan NEVER CAME ON. When I replaced the V cylinder sender, then the fan came on at 220F.

My point here is that with the POS OEM senders, then engine can actually be overheating without you really knowing. And when aluminum heads overheat on cars, you usually blow a head gasket. So some warping here might be a very easy thing to happen with these false conditions.

OEM senders were about $100 USD (each!) years ago. The Bosch (also NAPA & others have replacements) about $20 / each.

I was also able to verify the intermittent-cy of the readout sender in boiling water, as my VOM would go "open circuit", while watching the resistance fall while heating. (they're NTC's, with are inverse resistance as the heat rises)
 

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So my recommendation is to replace the OEM POS senders (soon!!!) with aftermarket ones. I've also verified the temp area on engine/plumbing with an optical pyrometer. The replacement ones are spot-on.
 

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Discussion Starter #16
So my recommendation is to replace the OEM POS senders (soon!!!) with aftermarket ones. I've also verified the temp area on engine/plumbing with an optical pyrometer. The replacement ones are spot-on.
You have part numbers for the Bosch? are both are the same and which one is for the ECU? I have plans to add a aftermarket temperature gauge...I can make an adapter to splice into the upper radiator hose...
 

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Do the search in here. Maybe even at the top for "replacement parts".
 

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Discussion Starter #18
I found the NAPA part number...the temp sensors also fit some Nissans and Ferrari...I pulled off the rear head and the oil weeping situation was the same as the from, by the exhaust port..Again I checked the head to cylinder fit and nothing is warped..If the head and cylinder fit becomes poor when the engine is running normally, then no amount of machine work will fix that..
New timing belts and I'll ride the bike this spring to see what happens..
 
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