RT Rebuild and questions

[DewCatTea-Bob]

[quote="wcorey"]
" That's likely in Kev's "1968 250 MK3D rebuild - ex W/C Oil Pump" thread... "

____ Right, that's it ! _ I eventually would've recalled the title & found it and posted a link myself, but/so thanks for the help with that.



" A 40w headlight should indeed be do-able with a stock w/c 6 pole alt, "

____ As I've pointed-out in other/past related threads, the stock 6-pole alternator/charging setup (with it's included pull/pull effect) can well handle a 6v/45w* headlight running during normal/regular riding, (which doesn't include repeatedly sitting at idle in city-traffic for extended periods with lights left turned-on).
(* That's equal to a 12v/45w as well).
__ If we were considering retaining the R/T's stock 4-pole alt.output, then a 35 or 40w headlight could still be managed, so long as the average-RPM didn't stay too low for very long.


" The 'breakeven' point where the alt will produce enough power/voltage to charge the battery with the lights on "

____ This must be a misstatement by Bill, as he certainly knows that 'break even' is the point when the battery neither receives nor looses any charge !


Dukaddy-DUKEs,
-Bob

[graeme]

Light springs.



Turn down the closing rocker to fit the springs.



The white section needs to be lapped down, This is the first part that closes the gap between the opening shim.
The tight spot then moves towards the "flat" section of the closing rocker which then needs lapping.
Does this make sense?
If you remove the springs, shim the closer as normal and shim the opener tight, like .03mm and roll the cam through 360 degrees it will close the .03 very quickly and bind.
Even set at .1mm most cams I have seen will bind where the valve starts to open or close.
It takes a long time to do with a diamond lap but the opening clearence remains constant throughout 360 degrees.
Some 450 desmo cams are worse than others.
graeme

[wcorey]

Here we go... reminiscent of whether voltage exists in the alt if there is nothing there to use it...

____ This must be a misstatement by Bill, as he certainly knows that 'break even' is the point when the battery neither receives nor looses any charge !

Which is what my statement was meant to convey, guess I wasn't concise enough. Seems to me the alt first has to get the battery up to the point where it "neither receives nor looses any charge" to reach the breakeven point and either exceeds it or recedes from it on a constant basis. By your definition, it could be argued that the breakeven point doesn't even exist as an actual state in time as it never "stay's at" breakeven but is rather always before or after.
I can go as far as to amend it to...

" The 'breakeven' point where the alt will produce enough power/voltage to maintain a full and/or reasonable level of charge to the battery with the lights on "

...but I stand by that as a reasonable definition.

It's funny, you do keep me on my toe's, Bob. In my previous post, I almost replaced "...enough power/voltage..." with "...enough power to produce sufficient voltage..." in case you decided to call me on that. Lucky I didn't just use "...enough voltage..."

Sorry Graeme, some 'old business' revisited...


Bill

[wcorey]

I like that spring mod, very clean implementation. I hear some don't even run springs, I guess compression closes the valve once running and the springs are only there to facilitate starting. So if you run zero closing clearance the springs wouldn't be necessary at all but since it seems apparent that most of the cams don't allow zero, I have to wonder if that's why the springs were originally used.

I went through a similar arduous process with my cam, even knowing I could get away with the extra clearance, it just didn't seem right to run it that way. Didn't take the extra effort to get it spot on as I was concerned about going too far and having to resurface other area's of the cam to get it back, big improvement though.


Bill

[DewCatTea-Bob]

By: graeme...
" shim the closer as normal and shim the opener tight, "

____ So exactly how are you shimming the closer "as normal" ? _ As however done, that's no-doubt the source of the binding issue ran-into ! ...
__ It's understandably obvious that Ducati MUST have meant for the recommended "0" closing-clearance to be set at WHATEVER point in the camshaft's 360-degree rotation where it can actually be done WITHOUT BINDING ELSEWHERE within the complete rotation, and NOT set to zer0 at TDC (as many assume) !
The reason Ducati could get-away with the sloppy cam-ramps (which can lead to possible binding), is because they depend on the valve-springs to complete the v.closing-job that's merely only mostly done by the closing lobes & rockers. _ So therefore the only reason for actually needing the closing-clearance to be set at zer0, is to cut-down on slop & noise as much as possible. _ And the resulting closing-clearance slop (up to about 1mm) is not a real issue !


" Even set at .1mm most cams I have seen will bind where the valve starts to open or close. "

____ Yeah but, ".1mm" at WHAT rotation-point ? _ TDC ? _ If so, then that's obviously of-course the WRONG place to shoot for '0' closing-clearance ! _ Logically quite simple actually.


" It takes a long time to do with a diamond lap but the opening clearence remains constant throughout 360 degrees. "

____ I hope my view-point is not misunderstood though, as do I agree that the consistency-work (done at the points of possible binding), is indeed fairly 'nice' to have, and perhaps even necessary if closing-springs are eliminated. _ It's just that most others don't really have to feel the need to have their-own D.cams reworked to become so consistent (in constant clearance) ! _ As it makes no useful difference so long as the valve-springs remain functional.
Still though, the unneeded consistency-work makes for a sort of hobby-pleasure, (if nothing more).

____ Thanks for the great pix !
And your work shows your dedication to perfection. _ Nice to have your membership with us !


Duke-Cheers,
-Bob

[DewCatTea-Bob]

By: wcorey...
" Here we go... "

____ If you say so Bill.


" reminiscent of whether voltage exists in the alt if there is nothing there to use it... "

____ That statement seems as if perhaps you're meaning to mention that in the same vane as when someone suggests that there's no sound made if a tree falls in the forest when there's nobody around to hear it,, and that's of-course absurd.
And if that's indeed the case, then apparently you didn't properly grasp my intended conception before. _ Which is that no specific amount of voltage exists with a running alternator, unless it is connected to a load-circuit. _ So before there's any connected circuit involved, there's only merely 'potential' created (by the running alt.).
And 'potential' is the actual driving-force which forces current through a circuit which THEN creates a 'voltage' . _ As 'voltage' is actually a measured amount of 'potential', and before potential interacts with any circuit, it's merely just POTENTIAL-voltage ! _ Which is clearly where the mere term "potential" had been logically coined-from.
So it should be clearly understood that an alternator by itself doesn't produce any particular amount of 'voltage' until a circuit-load has been established (across the alternator's output).
So thus whenever it's been stated that an alternator is 6-volt or 12v, that indication has been simply dumbed-down or else it's expected that the reader must understand that the particular stated rating is expected to be in conjunction with the intended power-load system.
__ It's fairly understandable that many of those who've been over-exposed to the quite common misuse of such technical-terminology, would thus become inclined to develop a mind-set which tends to block their openness to properly comprehending alternate conceptions, such as this one now brought-up.
I hope I've finally put this concept into wording which allows you to finally get a sensible grasp of.
__ Is there anybody who doesn't 'get' the conception (concerning actual voltage-creation), which my chosen-wording has meant to make clear here ?


" Which is what my statement was meant to convey, guess I wasn't concise enough.
...but I stand by that as a reasonable definition. "

____ Yes, it was fairly reasonably worded, and those who understand what's actually meant by 'break even' no-doubt knew exactly what you had really meant. _ But I wanted those who don't yet completely understand, to realize the ACTUAL meaning of the established term "break even" (in regards to charging-systems).
Cuz as you had it worded, it was possible for someone to think that the battery is receiving some amount of actual 'charging' during 'break-even',, when actually in fact, the break-even point is when the RPM is exactly at the rate which has the charging-system producing the exact amount of power being consumed by the load-system, which also thus leaves the battery effectively out of the loop, (although pulses of insignificant current-flow may actually be passing in & out of it during the pulsating-DC of the charging-system), as it can then neither charge-up nor discharge-down.


" By your definition, it could be argued that the breakeven point doesn't even exist as an actual state in time as it never "stay's at" breakeven but is rather always before or after. "

____ It's not really my-own definition, as it's a term with a long-established understanding,, and it's of-course pretty-much always meant to be in regards to a specific RPM, thus then a STEADY-state !


" you do keep me on my toe's, Bob. "

____ Well that's good, at least for those who don't already know enough to realize what your chosen wording must really mean to convey.


Content-Cheers,
DCT-Bob

[graeme]

Hello Bob,
I'm new here and don't intend to offend, so forgive me if I do,


I set the closing shims at 0. not by measuring but by feel with the springs removed and one closer at a time, so I can feel the interference.
Not particularly at TDC but where the closing rocker is keeping the valve closed by its curve.

Then fit the opening rocker shimmed tighter than the Ducati recomended clearence. This is NOT what I run the engine at, just on the bench.
I know the closing rocker will rotate freely as it was the first one set.
Rotate and feel the closing gap dissapear and make it impossible to keep turning the cam.
Even if the opening shim is set at Ducati recomended clearence most 450 desmo cams I've seen will close the gap to nothing or bind, damaging rockers and cam lobes.

This is a desmo cam that shouldn't require springs at all, and the bear traps that are original must sap what little power there is and also load the bevels and Oldham coupling unnecessarily.
I understand why Ducati used these springs on their first desmo released to Mr public.

A desmo cam should maintain the opening clearence throughout 360 degrees (without springs fitted) or risk damaging cam or rocker surfaces if and when the clearence closes up due to heat expansion. (or poor grinding)

Take the springs out of a 450 Desmo head and set the clearences as per the Ducati manual then rotate it through 360 degrees by hand and you will see. Try the same test on a Pantah head or anything later, no binding as the cams are ground much better.

I agree that not every desmo owner has to do this, and I didn't for years, but it does make a difference to how they go.
And I do enjoy trying to set an engine as Dr T pened them.

Regards
Graeme

[DewCatTea-Bob]

" I'm new here and don't intend to offend, so forgive me if I do, "

____ One's wording ought be pretty-openly blatant before another takes any offense, since written-wording alone can often be somewhat easily misinterpreted.
I-myself dispense with any hugs & kisses within my chosen-wording, and so then my neutrally worded wording is sometimes thought-of as possibly negative (which is never meant to be the actual case).
So ditto back at you.



" I set the closing shims at 0. not by measuring but by feel with the springs removed and one closer at a time, so I can feel the interference.
Not particularly at TDC but where the closing rocker is keeping the valve closed by its curve. "

____ That's fine so long as what you mean by "it's curve", is the closing-cam's 'max.peak'.


" Then fit the opening rocker shimmed tighter than the Ducati recomended clearence. This is NOT what I run the engine at, just on the bench. "

____ Of course that is most helpful to fine the base of the binding-points.


" Even if the opening shim is set at Ducati recomended clearence most 450 desmo cams I've seen will close the gap to nothing or bind, damaging rockers and cam lobes. "

____ Then I take it that these DESMO-cams you've seen, were not from running engines and perhaps a bad-batch that had gotten disbursed in your country !? _ Cuz I've never come-across any such D.cams which came with any such excessive binding trouble.
Perhaps that batch was done poorly with the expectation of being used only with the stock valve-spring setup.
And here's an off-the-wall thought...
Maybe they were designed to be set thusly-loose so that the valve-springs would close the valves at lower RPMs, but at top-RPM (where the springs couldn't keep-up) there would then be somewhat a bit of expected valve-float which would effectively allow the average valve-lift to become wilder (at the higher RPMs where it's most useful). _ (Or-not), just a thought.


" This is a desmo cam that shouldn't require springs at all, "

____ Well if you really care to run without v.springs, then your consistency-work will have been worth-while.


Duke-Cheers,
-Bob

[wcorey]

____ That statement seems as if perhaps you're meaning to mention that in the same vane as when someone suggests that there's no sound made if a tree falls in the forest when there's nobody around to hear it,, and that's of-course absurd.

If a man speaks and there is no woman there to hear him... Is he still wrong?

And if that's indeed the case, then apparently you didn't properly grasp my intended conception before.

No, I understood where you were coming from then, and now also. My intention was to illustrate that I believe both the voltage/potential subject and the breakeven point could be looked at and understood from an alternate view. To me we agree on the basic concept, it's only an argument of terminology and semantics.
Your analogy to the tree falling is really quite relevant, in philosophical terms it can all be argued to no end...


Bill

[graeme]

Wouldn't be a lot easier to fit R/T TS parts (assuming they can be found)? Still 6v I realise but at least you'd know it all fits and works. Not to mention it keeps the bike "original".

As per:

http://www.philaphoto.com/imageLibrary/ ... m=54&pos=1

Phil

Hello Phil,
That sure is a nice looking TS.
I've never seen a real one only RTs
The "bolt on " parts are very hard to find in Australia. There are some reproductions but the quality isn't good.
As much as I would like to rebuild it to original, it will hopefully look close to what it was originally.
Thanks for the picture of your TS for reference.

Here is what I started with, unloved and unwashed, with hand me down baggy pants.



and where it is up to now,





Regards
Graeme