Good evening, all. I need the collective wisdom of the forum once more with regards to camshaft wear. I embarked on an oil change on my 4s the other day, and noticed a large amount of metallic particles at the bottom of the drain pan. I expected this to be rocker chrome wear, but I've pulled the cams and looked at the rockers, and while there are wear patterns present in them, there's no sign of chrome detatching. What I did notice, however, is that the horizontal inlet cam has a very different profile to the vertical one - the opening ramp is much flatter. I have a couple of questions:- 1) How do I confirm which cams are fitted? Is there a visible P/N, all cams seem to have a green paint mark. 2) Is this common? In any case, I've pulled the engine out, as if there are cam particles floating round the oil system they'll all need cleaning out. Will keep the thread updated as to progress......
Yes there is (should be) a code stamped somewhere on the camshaft, should include O (horizontal), V (vertical), A (intake) and S (exhaust) somewhere in there along with other letters/numbers to denote the model. See; https://www.ducati.ms/threads/camshaft-markings-id-numbers.125509/ for some more info.
Just checked again, found the numbers - 1L inlet and A1 exhaust. Correct for an ST4s according to Brad Black's site.
So I decided the prudent thing to do was to pull the engine and strip for inspection, figuring that it's really the only way to find out what's caused the significant cam wear and also to make sure there are no metallic particles left hiding anywhere. Leakdown testing revealed one leaky exhaust valve on the vertical cylinder, but not a huge amount of air escaping. Sooner than i thought, I had a wheelbarrow and an engine on the floor:- Thought that my original oil change sticker needed updating.... Removing the heads revealed the bores in reasonable condition, with minor carbon build up around the tops of the barrels, Piston skirts show some scoring. Removing the big ends revealed copper on both rod halves of the shells. Oil pump cover shows signs of scoring too, which could need polishing out. The gears seem in good condition, subject to measurement. Next, taking the heads apart for detailed inspection of the rockers and valve train.
Have been working on stripping the engine over the last few weekends. Found a few things that look like they need attention, but nothing that can't be fixed. Found some wear to the rockers and shafts, with what look to be marks from the closing springs digging into the shafts. The valve guides measure as being in the last few mm, and generally above the clearance limit stated in the manual, so it looks like a head refurbish is on the cards, as replacing valve guides will require checking and recutting (or replacement) of the seats. I made myself the puller to get the primary drive gear off the crank taper, which worked surprisingly well - excuse the welding! Thanks to @buzzer for the info on the puller - much better than spending quite a lot of money on a tool I may only use once. Once the cases were apart, I was able to remove all of the various bearings from the bottom end, and catalogue them so that I may find alternative sources for them than the main dealers. The only one I can't find in the aftermarket is the clutch-side main bearing. It looks as if one of the mains has been spinning in it's bore, so that "bearing holder bush", as it's called in the parts manual, will need checking for size and replacing if necessary - I did manage to score this NOS inlet cam on eBay in Germany for £9, and have another on the way from the US, so parts are out there, they just take some finding! Will try to keep the thread updated, if anyone's interested?
To update this, I've been continuing to strip down and inspect the condition of the engine. After confirming the valve guides were out of spec with a bore gauge, I decided to remove them. The factory manual mentions a special tool, which I had a go at making:- Tool allows driving out of the old guides, and the conical part and the highly accurate engineered spacers make sure the new ones will end up in the same place. Heating the heads up slowly, in an oven, per the manual, allowed removal of the old guides with a few hefty taps. I've now got the engine stripped as far as it will go, have measured everything I can, and will now start to clean and repaint cases before compiling the shopping list for new shiny bits!
Small update to this, in case anyone's interested. Been busy stripping the old paint off the various parts, ready for a proper cleaning and installing bearings, valve guides and seals before some new paint gets applied. I haven't stripped the barrels yet, as I need to get them re-plated. I've read some of the threads on here about the various suppliers of Nikasil. Does anyone have any recent experience with the suppliers - Langcourt, RCS, Poeton Aptec, etc? Also, to go with the new bore surfaces, I'm looking at either using my old pistons with new rings, or finding some new Ducati pistons. Alternatively I've found that Wossner do a set of forged pistons, but from the information I've been sent it looks like they're higher compression than standard. Has anyone run a high-comp piston? I would look to remap accordingly.
I always use Langcourts can't fault their work/quality. They match the new bores to your pistons. Forget the lumpy pistons, just skim 0.6mm off the heads for exactly the same result. However you'll need to dial in the cams after doing this. Steve R
Thanks Steve, I appreciate the response. How much roughly will removing 0.6mm from the heads raise the compression? I now have a set of the later OEM adjustable cam pulleys, and will be dialling the cam timing in when the engine is built.
OK, I have a burette so can measure the chamber volumes once I get the new valves in. Would you expect any issues with 12:1, such as having to use Super Unleaded all the time? Any suggestions over cam timing to suit, considering the short duration '4s inlets? I was planning to use something like Brad Black suggests on his site.
At 12-1 I'd run it on Super/Shell V power and have it mapped using this fuel. I'd also go with Brads suggestions. Steve R
Some updates in case anyone's still interested. Installed the new valve guides yesterday afternoon - which I was putting off as I really wasn't looking forward to putting them in - I had visions of getting them stuck if the head cooled down quickly, or worse driving them in too far. In the end, it was all a bit anti-climactic, and took about 5 minutes! I then left them overnight for the heads to cool down. So today I have honed the guides to size using a FlexHone, to the service manual clearance of 0.03 - 0.045mm (all came out towards the upper end of the as-new spec). Then the valve seats were recut. I'm not sure if these heads have had valve work previously, but the outer diameter of the 45° cut started out well above the service manual figures (29.6 & 35.6mm OD) and were definitely bigger than the ODs of the valves. The seat widths were also far too wide, so these have been brought back down using the 30° and 60° narrowing cuts. Finally all 8 valves got a super-quick lap with fine paste to check for consistent contact around all of the valve seats. The factory service manual states that no lapping should be done after seat grinding, but as I'm using hand-driven cutters and not a solid Serdi/Sunnen-type valve grinding machine I see no reason why a quick lap would do any harm by removing any machining high spots. All of the valves now seal against a combustion chamber full of brake cleaner under their own weight - no springs or closing rockers fitted yet.
Does anyone know where to get ThreeBond 1375B thread sealant? It's for the crank gallery plugs (1 x large and 2 x M8s). Have ordered from a place online but just received an email saying it's out of stock. Any suitable alternatives from Loctite? I've tried searching but have got that many different numbers floating round my head I'm totally confused!
Have you tried Ducati? It’s double the price from them due to the Ducati logo on the tube but they probably have it in stock. Edit: oops. My bad. I didn’t read the post properly, I read it as gasket sealant. Apologies .
Time for another small update. Managed to get all of the castings cleaned and painted, apart from the barrels which I need to send off for replating. Have also started putting the bearings and seals into the crankcases, so that I can find out which shims I need for the crank and gearbox shafts. The service manual says to aim for 0.30mm preload, is that the general consensus? Next steps are to put the crank into the cases and measure the endfloat, and to continue putting parts back into the bottom end.
Spent this weekend looking at the crank and gearbox shaft shimming. The crank was straightforward, using two thinner shims as mentioned in the Service Manual. With a 1.9 and 1.95mm shim fitted, I get 0.15mm endfloat, so need another 0.45mm of thickness to get to the factory setting of 0.30mm. Easy. The gearbox wasn't playing ball quite as easily. After re-assembling the gearbox as per the parts manual, there was an obvious issue with 1st gear not rotating on the shaft, which I think is due to a missing washer on the diagram. The parts diagram shows this:- Which gives the end of the output shaft looking like this:- But that doesn't control the position of 1st gear properly. Luckily, I'd found that I had a spare bit, so deployed it at this opportune moment:- Betterer. The needle bearing and 1st gear are now held in place. This output shaft isn't the original one from this engine, I'm replacing it as the original one had damage to the sprocket splines and sprocket retaining clip groove - the end float ended up at 0.83mm against the spec' of 0.05 to 0.15mm = new parts required. The input shaft started out with virtually no endfloat at all, using the original components. Parts from a second 'box gave up a shim 0.12mm thinner than the original, which has landed us at 0.08mm endfloat - almost too little to feel. This is still pretty tight so I will order a thinner shim to see if I can get something a bit bigger without exceeding the as-new spec. I did check that all bearings are properly "home" to make sure I hadn't made a mistake. Finally, I checked the weight of the two NOS pistons I'd located. There seems to be a huge difference in weight between them - almost 8g! I'm not sure if it will be possible to get those identical - not sure what to do with those. The pistons appear absolutely identical - same P/N, same markings inside, same features. I can't see where 8g comes from!? During the week I'd been preparing other bits and pieces for the rebuild. I designed and 3D printed two valve/shim holders so that I can take the valves out of the heads to clean them. I've also made two supports to allow end-to-end balancing of the connecting rods, As I'm using the later adjustable cam pulleys, the Laser cam holder tool won't work, so I've made a spanner to hold the outer part of the cam pulley whilst the nut is done up:- Hopefully an order of some shims and other odds'n'sods will allow the bottom end to be built up, awaiting opening rocker refurbishment and cylinder re-plating.
