1968 250 MK3D rebuild - ex W/C Oil Pump

[machten]

This post is following on from my last post in the unrelated topic here:

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=434&start=10
I've started a new thread so us to not contimate that topic. I previously advised of cam and rocker wear on my 68 250 MK3D...

rocker1.jpg

Cam.jpg

DCT Bob advised..

____ I doubt that incorrect valve-shimming (for under 3k-miles) would result in such excess wear !
__ It's difficult to be very sure without hand-inspecting myself but, those surfaces look as if they've been ran for over 500-miles with fairly-badly fuel-diluted sump-oil, or pretty-much without any pumped-oil for roughly 150 to 250 miles of normal running.
So if you're not sure of the actual cause for that abnormal wear, you should also check that your oil-pump is really working as it should ! __ Here follows a link to a related post on the subject ...

And referred me to the thread:

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=252&hilit=oil+pump which i have now read (and found very informative, too, I might add.) I didn't post in that thread as it progressively became more specific to camshaft data.

So, I have a question or two regarding oil flow. With the head off and with the barrel held securely in place, I used the kickstarter to see if I could generate any oil flow up through the oil path in the barrel and out of the dowel pin (this reduces the oil way to about 2mm diameter, is that correct?). Sure enough, after about 4 or 5 workings of the kickstart at about normal kickstart speed, oil began to appear from the oil way. It wasn't any "gusher" or anything, more a slow flow of perhaps 1/2 cc per "kick". What should I expect to see?

regards,

Kev

[Bevel bob]

I would go right through the oil system starting with pump overhaul,check bush in timing cover and fit a roll pin restrictor in the cam at the drive end,also what oil do you use.The system is low pressure and will not do much at kickover speed.

[DewCatTea-Bob]

" I previously advised of cam and rocker wear on my 68 250 MK3D... "

____ First, I have to say that before (within that other thread), after I looked-over your two posted pix, I then failed to note that they were of DESMO-type parts, while offering my thoughts about the cause of the wear. _ So now I need to point-out that it is indeed reasonable to suspect that somebody in the past may have adjusted the opening-rocker/valve-clearance incorrectly & too tight, so as to help cause undue wear of the follower-face & cam-lobe, however it would take a grossly incompetent (non!)-mechanic to adjust the settings so badly as to cause any such wear, (and the closing-rockers would then also show a bit of wear as well) ! _ So I still doubt that the shown wear was caused by miss-adjusted clearances.
But also now that I realize that Kev's Mk3 is a DESMO-model, I was very likely wrong on my previous assessment... In order for DESMO-type opening-rockers to get so badly worn as shown, the engine would've had to run over 800-miles with fuel-diluted sump-oil, or be run with no pumped-oil for 250 to 400 miles, of normal riding.


" I have a question or two regarding oil flow.
. . .
more a slow flow of perhaps 1/2 cc per "kick". What should I expect to see? "

____ Everything you described was as ought to be, and while I can't confirm your "1/2 cc per kick" estimate, it seems about close enough (to normal), that I'm pretty-sure your oil-pump is NOT the cause of the cam & rocker wear.
__ You should check the oil-passage through the cyl.head, by making sure that oil, (not just pressurized-air), can flow freely though, (and that nothing has gotten stuffed inside there, to cut oil-flow).
__ I suspect that either the oil-pump was at some time once repaired, or previous owners neglected to keep the petcocks turned-off, and thus running (between normal-spanned oil-changes) AT LEAST ONCE with excessively fuel-diluted oil ! - (Although from what I see of the cam-follower, I'd more so expect a lack of oil rather than diluted-oil.)
____ So what are you thinking of doing about your unfortunate discovery, Kev ?


Hopeful-Cheers,
-Bob

[machten]

Thankyou for your prompy replies, Bob x 2.

I would go right through the oil system starting with pump overhaul,check bush in timing cover and fit a roll pin restrictor in the cam at the drive end,also what oil do you use.The system is low pressure and will not do much at kickover speed.

I'm using straight 50 weight oil (and it's was about 35 degrees C when I was testing). Can you tell me more about "a roll pin restrictor"?

Everything you described was as ought to be, and while I can't confirm your "1/2 cc per kick" estimate, it seems about close enough (to normal), that I'm pretty-sure your oil-pump is NOT the cause of the cam & rocker wear.

What I'm seeing in oil volume appears roughly consistent with oil delivery per cylinder on a twin (that I am much more familiar with), so I suspect the pump is OK too, but seeing as I'm working in the area anyway, I have all the gaskets and it's a new bike to me, I'll do it properly and strip the pump for a look. It wouldn't be the first time I've found interesting things in oil pumps!

You should check the oil-passage through the cyl.head, by making sure that oil, (not just pressurized-air), can flow freely though, (and that nothing has gotten stuffed inside there, to cut oil-flow).

Yes, I'll try squirting some oil through it tonight.

I suspect that either the oil-pump was at some time once repaired, or previous owners neglected to keep the petcocks turned-off, and thus running (between normal-spanned oil-changes) AT LEAST ONCE with excessively fuel-diluted oil ! - (Although from what I see of the cam-follower, I'd more so expect a lack of oil rather than diluted-oil.)

I know it to be the case that the oil was being contaminated by fuel through a combination of leaking petcocks and poor sealing float needle before I got the bike. This bike was owned before me by a girl who had no idea whatsoever about bike mechanics (never mind old Ducati mechanics) so 500+ miles on fuel contiminated oil is more than possible. I've replaced the petcock rubber seals. Unfortunately this bike has a non standard VHB carb (should be SSI) with the non replaceable float valve seat and even with a new needle I can't get it to seal 100% (close, but not quite). I'm intending to give the seat a little hone when I get to finalising carb set up.

So what are you thinking of doing about your unfortunate discovery, Kev ?

Well, beside the above, I've sent my rockers off to be repaired and am chasing down a replacement cam. I'm going to leave those at stock radius and look to aquire over time another set in need of repair that I can try a different radius on later.

A friend with many singles has reported good things about about using VeeTwo's desmo cam with H/C piston (which i have) and megaphone exhaust (which he'll lend me) in some of his bikes and I know where there is a new one of them at the right price, so despite some trepidation (particularly with the lift), in the interests of my education I'm going to give it a try. (The camshaft thread you referred me to was therefore of quite some interest).

VeeTwo desmo cam specs:

Inlet opening 54 degrees BTDC
Inlet closing 71 degrees ABDC
Exhaust opening 85 degrees BBDC
Exhaust closing 38 degrees ATDC
Lobe centres inlet 98.5
exhaust 113.5
Maximum lift inlet 12mm
exhaust 11mm
Running clearance inlet .1mm
exhaust .15mm

That's the plan for the moment.

Kev

[DewCatTea-Bob]

" (and it's was about 35 degrees C when I was testing). "

____ 35-C ?? _ Wow, you must be Down-Under somewhere ! _ The past couple of nights up over here (near Lake Michigan) have been down near -15C (& near -20C inland)!


" Can you tell me more about "a roll pin restrictor"? "

____ By stuffing a suitably sized split-pin (not quite fully inward, so it can be pulled-out), into the center-hole of the camshaft (at the bevel-side/end!), you then of course slightly increase oil-pressure out-through the feed-holes of the cam-lobes,, thus getting better use of the oil where it's more needed (than atop the bevel-gears).


" Yes, I'll try squirting some oil through it tonight. "

____ If you then suspect any stuck dirt left within, you might also then try high-pressure air-blasting a gob of cold grease through the passage, (but that idea is only for cyl.heads that've been setting-around wear various bugs may've made a home within).


" Unfortunately this bike has a non standard VHB carb (should be SSI) "

____ What model-year is YOUR 250Mk3-D ?
Cuz by mid-1969, the old SSI-carbs were replaced with those 29mm 'SquareSlide' models !


" even with a new needle I can't get it to seal 100% "

____ The VHB-models stock on DUCATIs came with the cheap nylon-type float-valve needles... Ya can get the rubber-tipped brass-type, (as used in MotoGuzzi-850s), which do the seat sealing-job somewhat better.


" I'm going to leave those at stock radius and look to aquire over time another set in need of repair that I can try a different radius on later. "

____ Best not to experiment with the rocker-arm cam-follower radius of DESMO-rockers, (unless you're willing to allow the closing-rocker lash-clearance to be left sloppy !
And even for nonDESMO cams, the increased-radius idea should only be employed with cams which have mild timing to begin with. _ (And no DESMO-cam is mild!, btw.)

____ I've taken the portion concerning the VeeTwo-cam over to a more appropriate thread, since that subject is of particular interest !


Hopeful-Cheers,
DCT-Bob

[Bevel bob]

As the head drains through the lower bevel gears and their bearings i would want to at least inspect them for damage from cam and follower particles.Also wash out the head and check that the oilway in the end cover is not obstructed with gasket goo,mine was!.

[machten]

As the head drains through the bevel gears and their bearings i would want to at least inspect them for damage from cam and follower particles.

Yep, for sure, Bob. I've already checked the bevels gears and they look fine - just normal wear. I've got some 6202 C3 cam bearings and 1202 ETN9 self aligning upper bevel bearings as spares for my twins. I'm going to replace them just as a matter of course seeing as I'm in there anyway.

Also wash out the head and check that the oilway in the end cover is not obstructed with gasket goo,mine was!.

Good point. I'll check that. I didn't look at it earlier.

I'll respond to DCT Bob's post after he's finished. (Assuming he survives -15C )

Thanks,

Kev

[DewCatTea-Bob]

" I'll respond to DCT Bob's post after he's finished. "

____ I've wanted it known why it often seems that I submit many of my posts before I've finished them, and now here's as good a time as any to explain.
__ There are actually several reasons...
First I should have it known that of about every three posts which I do get posted, there's one that I wanted to do but never got around to doing. _ So I've come to realize that if I don't at least get started on a post, then I'll likely never get it done ! _ (I'm sure there are others who realize how that applies to themselves as well.) _ So if I get myself at least started on a post, then not only will others then realize that I'm 'On It' & will likely get it finished within the day, but I'll also then have myself committed to go-ahead & get it completed.
The next concern is loosing text which I've thus far completed ! _ It's happened more times than I care to recall !! ... I'll have a good portion of my intended post all done, and often with just a little left to add, something or another will then happen that causes everything I've completed to be completely lost ! - I REALLY HATE THAT !! _ And whenever that's happened, I very often refuse to do it all over again ! _ So whenever I've typed enough that I'm at that precious point, I just go-ahead & post what I've done thus far (to make sure it's not going to get lost!).
And next situation, which I'm sure everyone's experienced while on-line trying to complete a post, is the never ending interruptions of your thoughts by the many various things which seem to need to happen around you're home at a time when you're least ready for it !
And also, there's of course the wife who doesn't seem to care at all that she's interrupting your concerted-thoughts with the most mundane trivial matters,, so to keep the peace, ya have to come back to what you're doing, later ! _ (And that usually means that thoughts which WERE going to be included within the intended post, are likely going to be forgotten to be included later !)
And on top of all that, I, like to watch the History-Channel(s) myself, and the interesting-stuff shown on them doesn't wait for me to finish, either.
And after such things as all of those (and still others) have taken their tolls, enough time has usually passed-by, that I need to log-in again, and I also wish to avoid having to do that, so I just go-ahead & post whatever I've gotten done thus far at the time.
__ Anyhow, when I'm finally done working on a post (for the time being), I then sign-off with: '_______-Cheers,-Bob' , and when I've later reread my post & am sure I'm done editing it, (which possibly may never occur), I then sign-off with 'DCT-Bob' .
____ Sorry for all of this ! _ And hope ya understand.


Good-Cheers,
-Bob

[machten]

" Unfortunately this bike has a non standard VHB carb (should be SSI) "

____ What model-year is YOUR 250Mk3-D ?
Cuz by mid-1969, the old SSI-carbs were replaced with those 29mm 'SquareSlide' models !

Mine is the 1968 "twin filler" model that came with the SSI. At some stage that got removed and replaced with the VHB 29 that the later models used. Pity really from an originality point of view, cause they seem really hard (and expensive) to find now. I've been told the VHB is a "better" solution, and I certainly have had no problems tuning them in the past on my 450 M3.

" even with a new needle I can't get it to seal 100% "

____ The VHB-models stock on DUCATIs came with the cheap nylon-type float-valve needles... Ya can get the rubber-tipped brass-type, (as used in MotoGuzzi-850s), which do the seat sealing-job somewhat better.

Yep, it's the rubber tip type I'm using, but still leaks a bit despite the float level being set correctly. I can only think it is seat wear or a small burr or something. Anyway, a minor issue that I'll get to soon.

" I'm going to leave those at stock radius and look to aquire over time another set in need of repair that I can try a different radius on later. "

____ Best not to experiment with the rocker-arm cam-follower radius of DESMO-rockers, (unless you're willing to allow the closing-rocker lash-clearance to be left sloppy !
And even for nonDESMO cams, the increased-radius idea should only be employed with cams which have mild timing to begin with. _ (And no DESMO-cam is mild!, btw.)

Yes, good point re Desmo. I didn't think that through very well at all. Something I'll bear in mind for my 450 M3 perhaps.

____ I've taken the portion concerning the VeeTwo-cam over to a more appropriate thread, since that subject is of particular interest !

Yep, saw that. I found that a quite fascinating thread and hope to add to it soon. Just waiting for the cam at this stage.

__ Anyhow, when I'm finally done working on a post (for the time being), I then sign-off with: '_______-Cheers,-Bob' , and when I've later reread my post & am sure I'm done editing it, (which possibly may never occur), I then sign-off with 'DCT-Bob' .

I read that somewhere in one of your earlier posts, so that's why I said I'll wait until you were done before responding. I've had to retype posts here before - so I know where you are coming from and in one exchange i recall we got a bit out of sychc (because we were too quick for each other!). I hope you didn't feel prompted to put in your explaination by anything I said. I'm just grateful this forum exists. Everyone has been a great help to me .


Kev

[DewCatTea-Bob]

" I've been told the VHB is a "better" solution, and I certainly have had no problems tuning them in the past on my 450 M3. "

____ It's true that the VHB-model is an all-around better carb, and I'd choose one over a SSI-model in any case !


" Something I'll bear in mind for my 450 M3 perhaps. "

____ Most 450Mk3s (as far as I know) came with the same cam as the 450SCR, and if that's the cam your 450 has, then it's performance should well benefit from the increased radius mod.
__ However, the real '450M3-camshaft' would likely be better (with stock-rockers) for your 450 !


" Just waiting for the cam at this stage. "

____ Do you know if that particular VeeTwo Desmo-cam (which you're getting) is the model that doesn't need the cyl.head to be modified ? _ I once heard that that manufacturer had a couple different DESMO-cam models, and one of them required a head-modification.


" I hope you didn't feel prompted to put in your explaination by anything I said. "

____ No, not really Kev! _ It's just something I've wanted others to realize long before you registered here ! _ I merely haven't wanted to place a post just to make those various off-topic rants of mine all brought-out, and I'm now glad that an excuse to have brought-up the matter (of my unfinished-posting), has finally occurred !


Contented-Cheers,
-Bob