Valve stem seal.

[Irezumi aka Reuben]

How difficult are these to replace. Worth getting specialist tools or just as good taking the head off?

Bike is and Aprillia SL1000 (Rotax V-twin engine).
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Pictorgraphicalfantastical

[Snod Blatter]

You will have to get the head off anyway, unless you have a very special trick to compress the springs enough to pick the collets out. Or Rotax built it differently from everyone else ever?

People have always managed to do this without the proper tool, but how they perform this feat of dexterity is beyond me. It is quite easy with the correct tool, but I would look into getting someone to do it for you if you can (after you remove the head(s) yourself).. Factor in the cost of the tool and it's not a lot more expensive, and it is a fiddly job.
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1994 CB250, 1984 CBX250RS-E, 1989 K100RS, 1995 TRX850, 2016 Z250SL

[Burnzy1989]

Well it's not a walk in the park . You will request a valve spring compressor to remove the Collets to alow the springs to be removed . But you will have to take the cyclinder head off. If you have no knowledge on how to take apart a engine or not conffident I would suggest you get some one who does as it might cost you more if it goes wrong

[Irezumi aka Reuben]

I'm good taking an engine apart. Just did some reading and was looking for a quicker way to do it.

Going to take the head off and replace the guides as well (which I will have to get done for me). Bike has near on 50,000 miles so a good chance to have a look at a full top end refresh.
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Pictorgraphicalfantastical

[sickpup]

[stinkwheel]

Ok. You're all gonna love this. Paddy especially.

You CAN do it without removing the head.

Rocker cover off, cams off and pack that camchain tunnel with lint-free rags. Don't fuck about, do it NOW!

Now you do need to make a valve spring compressor of some sort. A piece of flat bar with a slot cut in the end bolted to one of the rocker studs through an oversize hole so it can rock back and forth will do the trick. Something like the thing to the left of this picture.
https://www.britishv8.org/Articles/Images-V17-1/ValveJob-BA2.jpg

Or use the end off a more conventional one on a t-bar with a big heavy mate to push it down.

Now set the piston to BDC. Remove the sparkplug. Get some cheap, plastic covered washing line (not the metal cored stuff, the stuff with string up the middle) and shove as much of it as you can in through the spark plug hole.

Once you've done that, turn the crank by hand so the piston pushes the washing line up against the valves. Be sensible, just needs to be enough to stop the valves dropping out by gravity, not bend your conrod.

Deploy spring compressor (this job is WAY easier if there are two of you. One to compress the spring, the other to insert/remove the collets). Remove collets, springs and assosciated gubbins (a pair of tweezers and a good strong magnet are your friends here). Pop the old oil seal off, put the new one on, reassemble.

Rinse and repeat.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Irezumi aka Reuben]