got2dv8
What are the recommended valve clearances for 2v? I always go with the Ducati service manual specs. (thru '96)
Intake openers 0.102 (4)
Exhaust openers 0.127 (5)
closers 0.038 (1.5)
Robert
Lawson SP3
intake opener = 0.10-0.12 mm
intake closer = 0.03-0.05 mm
exhaust opener = 0.12-0.15 mm
exhaust closer = 0.03-0.05 mm
this according to the Haynes manual closest to hand.
got2dv8
Thanks but those are the same as I posted.😄 I'm really interested in if these are still ideal or if there are updated clearances...guess I should have been more clear.
Robert
griff851
Depends on how keen you are. There are assembly clearances and running clearances.
Running is 0.05 to 0.15 for openers, and 0 to 0.2 for closers. Yes it shit loads, but that's ducati's workshop wall chart, so that's what dealers service to.
brad black
closers 0 without drag, openers 0.10mm. that's what i use.
griff851
Edit. What dealers can service to. Not what they service to. My apoligies.
got2dv8
Thanks you guys! That's what I was looking for. I'm doing the valve clearances (900) for the first time ON the bike. All these years I've checked/adj them with either the heads off or the entire engine out. Though access is pretty good, I have to figure out the logistics ie. keeping the valves from falling, etc. I ended up shoving a nutdriver in the plug hole to stop the valves while the other jug is close to tdc. I guess you're supposed to do one head at a time... However, I haven't got the liberty of spare shims since I put together another SS from parts so I've gone at both heads at the same time. I'll just try my best to get the "0" closing gap and then assemble (remove the belt(s)) and rotate the cam to see if I have drag. Initially my openers all measured tight mostly 0.038 and my closers loose ranged from 0.064 - 0.104.
Robert
griff851
Fill the cylinder with air to stop the valve falling in. A leak down kit works best. But if you don't have one of them a compression guage and just compressed air will do it. I assume you have an air compresser that is. It doesn't need much air. I have heard you can use a bit of sash cord as well.
brad black
i don't understand this putting stuff in the cylinder to hold the valves shut. i just use the piston. it's already there.
got2dv8
I did use the piston but I tore them both apart at the same time... so I could measure all the shims. Then I reassembled one head to do one at a time. No worries.
Robert
griff851
brad black wrotei don't understand this putting stuff in the cylinder to hold the valves shut. i just use the piston. it's already there.
When you have to smack the shim with a hammer because the shim is jammed on the valve stem it helps. Also makes pushing down on the rocker and putting in collets on that
that shim that drags on the valve stem just a little easier.
brad black
don't you just hold the closing rocker down with a pin. then use the piston to push the valve up.
griff851
Nah, use a made up simple rocker tool that you use your thumb to hold the rocker down, also makes checking the rockers really quick. Horses for coarses I guess.
got2dv8
griff851 wroteNah, use a made up simple rocker tool that you use your thumb
I'd be curious to see how you made yours Griff. I've been trying to find something lying around to make one. I've got some alum plate...but looks like it would have to be milled or drilled to make a half circle to go under the rocker spring.
EMS sells one for around $40. I've got a nice lever tool for the 4v... It'd be nice to have one for the 2v. Yes a screwdriver works but it's fun trying to get the half rings out and in.
Robert
BARONROJO
Clearances depend on what you want to get... as always is a compromise....
For closers, the best is as tight as possible but NOT overtight: 0 to 0,05 mm. 0 can be checked if you push the rocker down or overcome the spring pressure and you can make the shim rotate with your fingers (and your thinnest gauge doesn't get in the place, of course). With tighter clearances at closing shims you minimize the possibility of valve rebound. Due to desmo, rebounds are very small and therefore engine performance is -almost- not affected and breakdowns due to valve flotation cannot take place.
BUT you minimize valve seat wear which is important and you're going to see why
What happens with openers? Let's have a look....
When the engine turns, the valve seat wear... slowly but they do as they're knocked by the valve several million times a ride. This is why you have to check your opening clearances, as on any other bike.
CASE 1
So, for the BEST COST/LONGEST INTERVALS OF MAINTENANCE, it's best to have them set at their widest clerance (0.12 - 0.15) with time and wear, clearance becomes tighter.
BUT in this case we have the influence of half rings. Ducati's half rings are NOT very good quality items and they become slightly crushed with time. With new half rings you soon have this effect and you lose what you got with a wide clearance. SO, in MY OPINION, it's preferable to re-use half rings for the sake of longer manteinance -finally adjustment- periods. Ducati states in their manuals that they must be changed but personally, I find NO reasons to do so.... Well yes, there are to cases, when they break -and they do- and if you wish to pay for them -and they're expensive for their crappy quality- and pay more money to your mechanic -if you are no a DIY guy-
CASE 2
You live in a country where it rains too often to enjoy your bike / you love motorcylce mechanics more that riding / you use your motorcycle just on some track days a year / you love to have as good perfromance as possible out of your engine.
In this case, you choose to have somehow tighter clearances, around 0,10, which has an important effect because.......
Camshafts rotate and, obviously, so do cams. They start opening the valve (or finish closing it -exhaust-) at the very moment they touch the shim. If clearance is lower, contact takes place sooner in terms of camshaft angle.
With this you get some degrees of andvance in the admision opening time and some degrees of retard in exhaust closing... and this is important becuase you have more gas inside the engine and therefore more power out the wheel -and valve overlap is a bit wider too-. It may seem incredible, but it is far more than a negligible effect!!!!! And that's why racing requires tight tolerances.
In this case is even much more important to re-use half rings to avoid their "crushing" effect and to keep the valves within their opening clearances.
The cons are obvious: it requires more frequent checking and adjusting and this is why it's the best advice for DIY lovers and/or motorcycles used not too often!
griff851
Just to add to the " compromise" component, having been doing a few heads of late. Something else must be taken into consideration. The cam profile. They are not perfect. It's something I've come across more on bevels than later models, but it does happen.
So you set up your clearances to ubeaut race trim. Your happy with your near to dam it 0, then you rotate the cam an it's got a tight point. So you have to either take out the cam and reprofile the second hardest material ever made by man, or shim out the contact spot.
A set of aftermarket cams I did recently were not pleasant and I seriously contemplated getting out the grinder.
got2dv8
BARONROJO wroteeven much more important to re-use half rings to avoid their "crushing"
+1 to that. I've always use the same half-rings. Only exception is if one is broken or if I'm doing a complete head from scratch.
Robert
Mr.R
There's a 3rd route that I favour and that's to fit MBP colletts/retainers in place of the 1/2 rings.
These don't crush down like the 1/2 rings and stay in spec for a very looooooong time.
Steve R
griff851
How long do you reckon Steve before we will have to change a shim? The amount of miles I'm doing of late, I'll be dead before I have to change one.
Mr.R
Well I haven't touched a shim in over 12,000 miles on my 851/916 and I don't fanny around on this bike.
It's still running as crisp as the day it left the dyno. 😎
The MBP colletts are still available from EMS, I've just bought some spares "Just in case" I ever lose one. 😏
Steve R
