parting darmah heads

[hashashan]

time is not on my side, have 1.5 months to finish the way too long overhaul.

got to the heads.
two questions:
1. when measuring the upper shim no pressure should be used right? (weired that both shims on the ex. were nearly 0 tolerance)
2. when measuring the lower shim, I can just measure the upper shim while pressing down on the lower and subtract the difference right?


now for the parting question :
I cant manage to open the nut holding the camshaft, I knocked back the washer that was cramped on one side to the nut(just this thing need to be knocked back, right?) while holding the camshaft from turning I cant open the nut(I know that it is reversed), how much pressure should be applied? should I use an Impact gun for that? or I'm doing something wrong.


thanks for the help

[Bern]

I had this in my bookmarks. It may help.

http://www.classicmechanics.com/news/ar ... -part-five

[hashashan]

thanks, already printed them ... very good articles.
managed to open the screw ... nothing an impact gun cant solve they were just bolted really hard in.
going to grind the valves to fit them inside in a few days.

seems like the project is finally coming to an end

[wdietz186]

You got the nuts off with a gun but how are you going to tighten them? When reassembling them,put the bearing block in the other side for support and find something softish to block the cam[thick aluminum, plastic,big brass punch,etc.] and wedge it between the cam lobe nearest the nut end and the head and tighten. Impact guns on hardened cast items sometimes break them where the threads end.

[Ducless]

Here is a little trick that I picked up somewhere for tightening the nut. Wedge a penny in the teeth of the cam gear. As you tighten the nut, the penny will be drawn in and not allowing the gears to turn. Since the copper is so soft the penny just gets mangled and causes no damage to the teeth. I think it is an old trick that Triumph mechanics use when tightening the sprockets onto the camshafts of old 650 and 750 twins.

[machten]

Wedge a penny in the teeth of the cam gear. As you tighten the nut, the penny will be drawn in and not allowing the gears to turn. Since the copper is so soft the penny just gets mangled and causes no damage to the teeth.

Perhaps I'm misreading this, but if the cam gears referred to are the top bevel set, I sure wouldn't be doing that. The teeth there are hard, but fine and brittle. I've seen a number of them chipped just through bad bevel shimming. :wah"

I use the wdietz186 method. Much better to tighten up against a hard chrome surface that has no risk of being damaged like a cam lobe using (as Bill says) brass or ali bar.

Kev

[Ducless]

The penny method worked extremely well on both of my heads. copper is even softer than brass or aluminum. Technically the only "real" method to tighten the nut is to use the official ducati camshaft locking tool. Most Ducati special tools are pretty hard to come by, so other methods are sometimes needed. So, I guess that my method is like any other piece of advice that you find on the internet, use at your own discretion.

[machten]

The penny method worked extremely well on both of my heads. copper is even softer than brass or aluminum.

So without wishing to start any arguement, or diminish what has been said already, I would have a few words of caution about this approach...

Firstly, whilst copper is soft, I would think that few coins of the last 30 years are made purely out of copper, as they are too soft to have a viable lifetime. I don't know what alloy US or British "copper" coins are made out of, but from 1966 until their demise in the mid 1990's, Australian copper coins were 97% copper, 2.5% zinc and most importantly, 0.5% tin. That makes them a low spec bronze. That 0.5% tin is what allowed effective axes, knives and swords to be produced in the bronze age when copper was plentiful, but tin was rare. I wouldn't be forcing one of those in between my bevel gears. That being said, I have when needs must, locked a primary gear using a cotton rag, but I woudn't do it with a bevel gear.

Secondly, I agree that the ideal is to have the cam locker tool, but IMHO, it is one of those tools that you really don't need unless you have a significant thread/nut problem anyway. ( I have ready access to one but just don't use it in favour of the wdietz method).

Kev