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ranton_rambler wrote:George, my 175 has no seals on the valve stems either. My 2 big block Guzzis are the same. I did consider getting the guides machined for seals on my 1000SP but was advised that they would wear more quickly without a little bit of oil.
Ian

I fitted bronze guides to my Guzzi small block V50 II seals not required. Sorry off Ducati topic.
Thanks for replies. Will go without seals and leave rocker seals sliding fit.
Had quote for rockers and camshaft refurbishment from Joy camshafts. £30 per rocker, camshaft maximum £120 depending on what needs doing. I thought price reasonable and will get this done later.

I believe the shape of the top of the guide can help oil control.
Avoid a conical bevel that could funnel oil into the guide.
But do have a bevel that sheds oil away from the valve, all the way from the bore to the OD of the guide.
Even if the guide has just a flat top, have a sharp 90 degrees where it meets the inner bore.
I don't believe any seal etc is needed for the exhaust unless the guide top is submerged in oil - not a typical situation.
But the inlet which is subject to suction should have some oil control arrangement.

Cleaning the head and found more bad workmanship. I have restored British and Italian bikes and have never seen anything as mistreated before.
Circlip groove that holds cam bearing bevel gear end is broken. See photos. I think that perhaps bearing not fitted all the way down, not enough room for thrust washer and circlip and has been forced in. Circlip was out of shape when removed with one end sticking up guessing not removed / replaced with circlip pliers. Rubbing marks on back of bevel gear from circlip loose in groove
Bearing is tight fit in head. Thrust washer is on bearing outer. Am I right in thinking thrust washer purpose is to hold bearing in place against end stop.
Now for the big decision. Would it work if bearing is fitted with loctite and leave out circlip and thrust washer. Any end thrust from bevel gear would force bearing against end not try to move it towards gears. Or am I looking for an easy way out and thinking wrong. Don't want the expense of another head. Any work around ideas gratefully received.
My shopping list for engine parts as gone over £850 and I have not even split crank case yet. As this is a 125 engine in a 175 frame not sure if I would be better off changing engine. Might be a problem If I ever came to sell. I know we have all got different ideas, your opinions are welcome.

George

I had a similar problem on a Spanish 200TS some years ago.
I made up a cutter and faced up the flange where the circlip fits and then fitted a stepped plate to hold the bearing
in.

The plate is held on with three small countersunk screws, loctited in.
I'm not entirely sure this was all necessary, as if the bearing is a good fit in the head, the thrust of the bevel drive gears will push the bearing towards the head anyway.
After quite a bit of juggling it all fitted and worked fine, although there is very little clearance to play with behind that top bevel gear.

Jon

George, firstly, I would try just loctiting the bearing; assuming all is well de-greased, loctite is pretty amazing stuff. Secondly, to be sure, you could just mill off two or three small circular areas on the outside of the bearing, and drill and tap 4 or 5 mm holes and loctite in button head Allen screws, so that the edges of the heads hold the bearing in place. Certainly it is worth trying before looking for another head that may have other problems.

Thanks for replies. Have had a think about it and will loctite new bearing in and if I think necessary, after setting up bevel gears, will put couple of centre punch dimples at edge of outer bearing to hold in.

Have been trying to sort out replacement piston. The one that was in the bike is not like any I have seen on internet.
According to manual I have largest over size is 56.2, this piston is 56.5 and dimensions are different to those on Piston King web page.
A) total height 72.6 Piston King 77.5
B) crown height my piston 14.2 Piston King 18.5
C) 24.5 both
D) 16 both
Wondering if piston from different model has been fitted giving lower compression ratio

I realise this will be for Italian not Mototrans but wonder if any difference and will be OK. Has higher crown but looks to have plenty of room in head. Photos attached.
Would I be correct in thinking that the only difference between 125 TS and 125 Sport engines would be piston and camshaft. valves same for both.

Having a piston 56.5 is going to be hard to replace.
You may have to either get hold of a barrel or liner nearer standard size and find a piston to fit, but finding Spanish or Italian 125 cylinders is not too easy.
I've come across this oversize piston problem before on Spanish Ducatis.
They sometimes come with pistons larger than was ever listed in the parts book.
I've had a Vento with a 77.75 piston, when the parts book only lists 76.00, 76.40, and 76.80. Makes finding new rings a bundle of fun.
I would start looking for a different cylinder or liner. possibly even a 160 one, although you would have to check it fits into the crankcase opening. It probably will.
Otherwise, you are correct regarding the cam and piston being the only difference between the 125TS and 125S motors. The valves are the same size.

Jon

Thanks for information Jon. Forgot to mention piston and barrel damaged by broken circlip. I have managed to get replacement used barrel that is suitable for rebore 56 or 56.2. I am hoping Italian piston would fit but not sure because of difference in height to one in bike.

The Italian piston should fit fine.
The Italian and Spanish 125 pistons had similar part numbers.

Jon