Strada Camshaft Oil Ways

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Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Strada Camshaft Oil Ways

Postby Duccout » Thu Apr 02, 2020 4:24 pm

As is the nature of these things, some things have turned out well and some less well. I have received my repainted parts and fitted them to the bike and today my shiny new Veglia Speedo arrived from Italy, along with a new exhaust ring nut, and it looks like I may get away with not having the exhaust port thread repaired. That is the good news.

Next I stripped down the head and because of the good condition of the bore, and the fact that it is on the original piston, I was expecting a quick grind-in of the valves and that would be it. Wrong! The exhaust camshaft lobe is badly worn and the exhaust rocker is destroyed, worn completely concave, while the inlet components are fine; coincidence? I'm not happy with the restriction in the feed side of the camshaft, while the roll pin in the exit side seems to give far too large an opening.

When I rebuilt my 750 bevel after 50000 miles, I found the front cylinder cam and rockers like new, but the rear assembly was worn. The front cam has no exit hole to feed the bevel gears, whereas the rear does, which means less oil for the cam lobes. Brook Henry of Vee Two told me that ALL of his cams are supplied with the exit oil way blanked off and he advised me to solder up the exit hole, which I did, and found no further wear on the rear cam or rockers. Brook believes that the bevels gain more than enough lubrication from oil working its way past the camshaft bearing.

I have a choice now between finding a used camshaft and rocker, or getting Phil Joy to reface them, although I don't know if the rocker is reclaimable. It's difficult to know what caused it now, and it could just have been a case of faulty chroming which flaked off and allowed the two components to wear.

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: Strada Camshaft Oil Ways

Postby Duccout » Sat Apr 04, 2020 3:24 pm

I've managed to find a used white camshaft, so will get Phil Joy to repair the worn rocker. It's funny, but it was always my intention to change the crazy profile Mototrans cam for something a bit more sane, so this has worked out ok. What with the white cam and the small valves my engine should be a real goer!

Ventodue
Posts: 627
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Strada Camshaft Oil Ways

Postby Ventodue » Sun Apr 05, 2020 8:38 am

You're making good progress, it seems, Colin. We will want pictures eventually, you know ...

Don't have enuf experience to comment on the rocker and cam wear, except to say that my 860 had scuffing and wear on its rocker faces in the rear pot, too. If Brooke says it's down to poor lube, it probably is ;)

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: Strada Camshaft Oil Ways

Postby Duccout » Sun Apr 05, 2020 10:14 am

Hi Craig,

So much of this stuff is weird. My 750 never showed any wear at all on the front cylinder rockers or cam lobes and that must be down to the fact that they receive more lube. Around 1980 Ducati changed the rear cams to versions with the exit hole to the bevel gears almost blanked off. On top of this, I'm not sure that the oil that is fed to the top bevel ever gets there; I had a gear gazer fitted to my 750 and any oil that came through the oil way was being flung straight off by the centrifugal force of the rotating bevel.

Back to weird: my Strada valves are distorted on the seating areas, that is, they are in the process of being pulled down into the ports, so that the seats on the valves are nearly vertical. This is nuts. John mentioned in an earlier thread that he changed his valve springs back to hairpins because the coil springs were too strong, but the coils are the same as fitted to the bevel twins, and I ran my 750 for 68000 miles and never saw any valve seat wear. Are the coil springs stronger on the Mototrans engines? Is it worth buying new bevel twin springs? Maybe the fitted length on the Strada is less? I don't know what the fitted length of the vee twins is, although I may have it somewhere in my books. Could my engine have overheated badly? I haven't compared them, but the Strada valves seem very thin at the seat area.

I'm in the process of recutting the seats, and hoping that there will be some seat left when I'm finished!

Jon Pegler
Posts: 326
Joined: Sun May 16, 2010 6:19 pm

Re: Strada Camshaft Oil Ways

Postby Jon Pegler » Sun Apr 05, 2020 10:21 am

The Strada, Forza and Vento models use double coil valve springs in place of the more usual hairpin springs.
The outer coil spring is the same as the 750GT and 860GT, which both only use a single spring.
The inner coil spring is from the 350/500 GTL parallel twin.
I think that the double coil spring arrangement is probably too stiff for normal road use.
It may be fine for racing, but sitting at tickover at traffic lights does not do the cam or rockers any favours.
I have fitted some of these motors with hairpin springs to relieve the load on the valve train and they behave like any other Ducati single, without excessive wear.
I have also built Forza motors with just the outer coil valve spring and they function perfectly well with just the one spring.
I suggest you try your new white camshaft with a single coil spring on each valve to help avoid so much wear in the future.

Jon

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: Strada Camshaft Oil Ways

Postby Duccout » Sun Apr 05, 2020 10:29 am

Hi Jon,

Yes that was my intention, as the 750 twin only used the outer spring and I'm certainly not going to be using many revs on the 250.

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: Strada Camshaft Oil Ways

Postby Duccout » Sun Apr 05, 2020 11:49 am

I've just found on closer inspection that the outer spring on the exhaust valve (the valve with all the wear) has been rubbing against the screw boss on the bottom of the cambox, badly enough to wear into the spring; could this be the cause of all the wear?

Ventodue
Posts: 627
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Strada Camshaft Oil Ways

Postby Ventodue » Sun Apr 05, 2020 3:29 pm

Duccout wrote:<snip>
I'm in the process of recutting the seats, and hoping that there will be some seat left when I'm finished!


I hope so too! :o . For the rest, "Best listen to Jon" :) .

(One side comment on what he wrote, btw: I remember that 860GT I had, the one with the scuffed rocker lobes, did, indeed, have double springs. Why? No idea ... The parts book only shows single springs, like wot Jon reports.

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: Strada Camshaft Oil Ways

Postby Duccout » Sun Apr 05, 2020 4:28 pm

Yes, the 860 switched to the dual springs, possibly with the GTS introduction, maybe because the factory had a load lying around after the introduction of the Parallel Twin......

I've cut a nice seat on the exhaust side, but the inlet is horrible, with a recess line around the middle of the seat. I've had enough now, there's no rush.

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: Strada Camshaft Oil Ways

Postby Duccout » Sun Apr 05, 2020 5:41 pm

As a further thought to this: the 750, with 40/36 mm valves is going to experience lower seat pressures than a 250 Strada with 36/33 mm valves. Valve springs meant for the control of 40/36 valves are going to be overkill for the control of 36/33 mm valves. I'm guessing that with the introduction of the Parallel Twin, and with a desperate need to cut costs by rationalizing the production line, Mototrans used as many common parts as they could between the Singles and Twins.


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