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Discussion Starter #1
Evening guys.

Now I've come to the end of modding my headlight, I've decided to tackle some minor issues that are affecting the bike at present. So while I had the lower & main fairings off, I noticed I had oil residue on the lower cylinder head around the midway point, and the engine itself has lost approx 1/2Ltr of oil in almost 8 months (not hugely excessive) and noticed elsewhere that there was talk of changing heads.

Now I'm not interested as such in changing cylinder heads or piston sleeves, but what I would like to know is, what does a top end rebuild consist of? what's needed for a top end rebuild, and what is the likely cost (£ or $)?

I'm not planning on doing this work in the short time we have left this winter, so genning up now in preparation for doing work to the engine next winter. Has anyone here done a top end rebuild on an ST2 944 engine? I'm planning on doing it around the same time as changing the clutch basket.

Cheers for any info you can provide.
 

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You're probably in uncharted territory here. There have been plenty of people repairing or replacing faulty components / gaskets in heads and cylinders, but I don't think a "top end rebuild" is common practice or commonly needed as normal maintenance after a given number of miles. It goes along with performance work at times such as installing high comp pistons, porting heads, cutting valve seats etc.

If you want to refresh things, normally that seems to involve cleaning carbon, checking and replacing if necessary valve guides, lapping valve seats and replacing all the gaskets and seals. You may have a change of heart if you were to look up the price of a set of piston rings! Most find it cheaper to buy aftermarket pistons...

I just looked up the price of rings on Ducati Omaha's site and a set (both cylinders) of rings are $430! A pair of very nice aftermarket pistons from FBF are $419 and they come with rings...

Point is, the days of needing to occasionally pull things apart to pop in a set of rings are over and not really needed. The cylinder linings on these bikes are coated with Nikasil, a very hard material. No idea what the rings are made of, but I can't remember reading of anyone ever needing new rings for general wear.

I think I'd find the source of the oil leak and fix that. Fixing the leak may involve pulling a head or cylinder to replace a gasket. If it does, maybe take advantage of that time to clean things up. If you're concerned, do a compression check to see where you are.

Otherwise, ride it!
 
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Mr Leakered
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There's no gasket on the ST2. I was shocked when I learned that a while back. Just some viton o-rings that I believe are prone to leaking over time.

Have a good one.
 

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Discussion Starter #4
Yeah, I was beginning to think the same to be honest, as you say, cost of piston rings on their own are pricey even when their at their cheapest.

I think I just need to change some gaskets/O-rings and re-adjust the rockers, other than that, I think she'll be good for another 20,000 miles (already at 63,000) had the belts done before getting her back on the road.

Just a quick question on engine running, if the temp sensor at the rear (one that communicates with ECU?) if that has malfunctioned will the engine run funny? And would it also be the cause of the rad fan not kicking in when coolant temp is excessive?

The owner of the bike before the person I bought it from (my former boss) said he had problem with cooling fan from the day he bought it himself. He bought a new fan, fitted it, but still the fan wouldn't kick in. So after some research, I think it's the vertical coolant temp switch, but just want clarification on the above.
 

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On the fan. What temp is it turning on? If it's turning on at all, it is not the fan. On the ST4s, the fan is controlled by the ECU via a relay. When the temp sensor that feeds the ECU reads a high enough temp, the ECU energizes the fan relay turning on the fan. I think the ST2 works the same way, or at least this schematic indicates it does.

https://dl.dropboxusercontent.com/u/71253082/Ducati%20ST2%20-%201998%20Schematic.pdf

My fan kicks on around 220 degrees (104ish C). Seems hot, but that's the way it is. You can install a manual fan switch if you like.

So if it's coming on higher than around 220 degrees, you can change the temp sensor to see if that makes a difference. If it's not coming on at all, check the fan by placing 12VDC to the terminals to see if it's working. If it is, go for the relay. I doubt it's the ECU, but you never know until you check the easy stuff.

And yes, a faulty temp sensor feeding the ECU can screw things up pretty well in regards to fueling and the fan. You can swap the sensors, front for rear, to see if you get a different indication.
 

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Discussion Starter #6
The fan works fine, I created a mini circuit from an old 12v battery direct to the fan, and it spun up nicely. I do think it's the temp switch which in turn controls the ECU auto cut in/cut out. I'll have to pull them both and swap them around to see how that gets on, or alternatively, hook up my multimeter to it and see if there's any change to the polarity inside the switch.

And I say the same as you as you, I doubt very much it's the ECU, more the switch which tells the ECU to turn it on/off.

I've had temps (last summer) reaching as high as 114c with no activation whatsoever, I have ruled out the fan, so just got the switch and relay to test! Where abouts is the relay for the fan?
 

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Where abouts is the relay for the fan?
Probably under the headlight fairing on the left side, but I do not know the ST2 well enough to say. An ST2 owner would have to pop in for that question.
 

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IF you want the engine to run well when warm, substitute a 220 Ohm resistor into the rear connector. The ECU will think the water temp is 207F.

ECU does control the fan on ST2.
If you place another 500 Ohms in parallel with the 220 Ohm, the fan should turn on. Not sure which relay it is, but I thought it was one of the 3 near the tool tray (under the seat).

If you need to start the engine cold, just unplug the resistors, leave connector open. ECU will run in enriched mode.
 

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Discussion Starter #9
Does anyone have a part number for these switches? I've had a look on the sticky topic for suitable alternatives, but the only one I can find on there is for an engine air temp? My Ducati Parts Catalogue lists them as: 552.4.013.1A, is this the correct item?

I know my local stealership sell them for £60 each (approx $85) so I would rather get a suitable alternative that won't break the bank, and hopefully resolve my overheating issue. I may go down the resistor route should all else fail, and fit an override switch onto the fan.

Thanks for the replies so far guys.
 

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From either the third or fourth post in the "equivalent parts" sticky:

NAPA TS5520 for the coolant sensors.

I have not tried it myself yet, just going from what has been posted.
 

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Discussion Starter #11
I did notice today while I had the bike in work, and some reasonable sunlight, that the radiator is rather well caked with road grime (mud/dirt), so this would explain the rapidly rising temp I seem to have at low speeds.
 

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The Napas seem to work OK and my original was still OK after 15 years. I may have a spare lying about.
 

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Any brand (Bosch, NAPA, etc) other than the Jaeger ones that Ducati provides are better. Both units failed on my ST2. It's one of the 1st items I replaced when I got my ST4s.
 

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I use the OEM relays, but I do keep a spare of each on board! Too many stories. One of these days I'll go the SSR route like DavyJ did.
 

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Chris,
I had a spare set of heads rebuilt and I was told by the re builder that he doesn't put new rings on unless they are damaged or the cylinders were damaged. I was told to reuse them and to reuse the base gaskets and to just spray them with gasket spray. I have about 8k since I put the rebuilt heads and I have zero issues.
Cost with vary with who you get to rebuild them, some people like to use new valves (if available). The shop I had rebuild mine did a light cut on the seats and valves and re shimmed everything with in spec. Good luck
Bill
 

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Discussion Starter #16
Hi Bill,

Thanks for the info, I'm now however contemplating just replacing a couple of gaskets (which one(s) atm I don't know) it all depends where the oil is leaking from.

As for top end rebuild, I've become less inclined to do it now. Thinking of just adjusting the rocker clearance and general engine tidy up. Does anyone know what paint is used on the engine case? Mine is looking a little flaky (light corrosion) so thinking of wire brushing and repainting after I've had the work done!

On a side note, how do you guys clean the external areas of your radiators? (Between the cooling vanes etc...)
 

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how do you guys clean the external areas of your radiators? (Between the cooling vanes etc...)
When I have it off the bike (which isn't often) I spray it with a cleaner like simple green and let it soak for a bit. Then I just use a garden hose and and flush it from the back side towards front. I haven't had to deal with clogging, however. Most of what I am cleaning out have been bugs and general road grime. If you have actual clogging I'd say you could try the same method, but if it doesn't work well you may try soaking it in a bucket for a while. The thing I feel to avoid is being tempted to use a pressure washer for fear of damaging the fins.
 

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Simple Green is great stuff. I spray the radiator with each washing to keep the fins clear of bug guts. If really gunned up. Do like Dan suggested but I'll add my spin: use very hot water and Simple Green. Then blow the crud off with compressed air.
 

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Discussion Starter #19
Is this simple green just a normal household cleaner? Do you guys think a soft bristle brush would also be a good idea for more stubborn dirt?
 

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I'm not a fan of brushing the radiator. The fins are really easy to bend. How bad is it?

The Simple Green is the regular old house hold detergent brand. Buy the concentrate and mix 1:1 with water for super greasy jobs, 1:10 for regular old grime. I use this stuff all the time on my vehicles...safe for body work, alloy, rims, rubber, and the environment! Does a darn fine job as an engine degreaser too.
 
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