I am doing a clean rebuild on a 888 SP4. I am looking to replace the valve stem seal. They are a complete bum to remove though. I have also now bought a couple of pliers for the job and there is zero clearance between the seal and the wall of the head, so it is completely impossible to insert the pliers. Putting the pliers the other way is impossible as well since the handles cannot operate through the opening of the inspection cover. There does not seem to be a specific tool for desmoquattros, so I am a bit lost as to how to proceed. I do not want to go as far as changing the valve guides. How do you remove your Valve stem seals? What tool do you use? What to worry about to insert them back?
I got mine off with a hooked pick... wasn't too difficult, but installing the new ones was a bit of a struggle..I found it easier to lightly grease the insides and install them without the valves in place.
How did you use the hooked pick? Did you pry from under the seals? Installing I have read a few ideas - from using a valve seal insert tool and create a leverage to push in. Or use a socket and a long bolt through the valve guides. But for now, my challenge is to get them out.
I was looking for some information online and it looks like those Red ones are a bu99er to get off. I am wondering a little to keep them but with an engine that has not run in a very long time, I guess they have probably dried up and would be better changed. By the sound of it, cutting the metal band with a chisel seems like the main option. I have taken some pictures of the 888 heads - Looks like later designs made a better reserve for fitting a plier. I am likely to go for green ones as replacements. Does anybody know where to source them from auto suppliers?
as you said, a horrible job to remove if all original. As hinted at, any sturdy dentist-type pointed tools or small heel/pry bar (similar to below but with a bent end), definitely sharp-straight bladed or pointed is the only way. I have used modified pry bars in the past where close to the tip is bent to achieve around 90 degrees* but depending on how well hardened they are, how far the hardening extends beyond the tip, makes even this difficult to do. Ingenuity and invention is the clue, as you well know already. I've tried to find videos more info but without luck so far. * this is so the end of the tool can rest on the casting "floor" to achieve upwards leverage but even then, you only have 15 degrees or less of "prying movement" due to the confined space. Two prys would be perfect but "rocking" action applying tool 180 degrees alternately usually the most practical.
Tbh, I can't remember exactly the technique, but I know I didn't care about saving then...so was probably quite forceful in removal. I do remember inserting new ones with the valve stem flush with the seal top to help guide the diameters to the correct locations.
I've not had many sets of valve seals defeat my ancient set of 'picks', over the years. One was a modified Hillman Imp head that had been fitted with uprated seals from god knows what, but a narrow chisel used to cut down the side sorted them out. I also struggled to get the seals off a Riley 6 engine I was working on for a neighbour. It had been modified to use seals, and we needed at least one off each side intact to measure for replacements. I ended up sacrificing a good quality scriber by cutting the bent end off a few mm from the main shaft and grinding it into a flat, which popped them off nicely when used as a lever. As an aside, we ended up putting that back together without seals as it was originally built, because we found the valve guides had worn really badly over a very small mileage and needed replacing anyway. As for putting any seal in place, you really can’t beat the proper tool for each application. Simply a length of bar bored out to a sliding fit on the valve stem, then counter bored at one end so the rubber bit fits up inside and the end of the bar bears on the top of the metal sleeve. .
I replaced the seals on my 916, IIRC I used a pair of bent, long-nosed pliers to pull them off AFAIK 888 heads are pretty similar? (though looking at the above pic, maybe a bit more room in a 916?) As for fitting new ones, I used a nut/bolt and 'modified' washers to pull them into place rather than try bashing them in with a hammer - much safer and less likely to damage anything. Some pics;
tip of the iceberg stuff here, but fitting is, or providing valve guide diameter is reasonably correct for that stem-seal, fairly easy. You should always use a "draw-bar" that is similar in appearance and diameter to the valve stem - I wouldn't use the above with the threaded portion of a bolt adjacent to the valve stem lip upon fitting. Sometimes when stem seals are at the tighter fitting end of the acceptable fitting diameter spectrum, the seal will compress slightly and spread inward at the lip seal area (sometimes 2 or 3 lips over the years) and so could be cut/slit by anything other than a smooth surface.
I use long nose Vice Grip's to remove the old seals and have the genuine Ducati special tool to replace the new ones. I also fit car valve guide seals, they cost a small fraction of the price that Ducati ask for them and they're exactly the same part. Steve R
I was planning to use this approach too for insertion, except that I was looking to insert the smooth side of the bolt nearer the seal to avoid exposing the seal to the threaded bolt. If you see the space inside the heads that I posted for the 888, the casting is very different to your 916. A lot less clearance between seal and wall in the head. The thickness of a valve removal plier ends does not fit between seal and wall. And you can't position them top/bottom because then the pliers do not fit in the inspection cover anymore. The more I am reading about it, there does not seem to be any clean way without butchering the seals. and if I butcher the seals, I am thinking that I may as well carefully cut the metal band as it is probably the best way to avoid creating any damage to the valve guides.
I've got '91 851, '92 851, 888, 916, 916SP and 888/926 Corse "G" heads here and there's NO difference in the placing of the Valve guides in relation to the wall of the heads. Steve R
That's what I have tried and it works a charm. I am just "ashamed" having to attack them like an ape. Even if the intention is to replace them for new as bike had not been ridden in a long while, fresh rebuild and a bit of carbon deposit on piston, I don't feel right not being able to take a part out cleanly.
It's not possible to get squarely onto the guides which is why the factory tool is the shape it is. Similar in shape to a crows foot spanner. The tool part number 887130833 ensures you get a straight push on the seals. Check out the link below:- Ducati Superbike 888 SP5 WORKSHOP SERVICE TOOLS » SPECIAL TOOLS exploded drawing > oem-parts.hu Steve R
