oil leak and fork issues

[Scottish888]

Finally took my Ducati 250 out yesterday for the first time.
When I got back I noticed a little oil under the sump, looks like it was coming from the centre joint or/and the bottom of the case where it looks like it should have a long bolt through it. There was nothing in there before, should there be?
I rebuilt this engine so carefully, the faces seemed sharp square and clean, I never used any sealant, just lightly oiled gaskets before fitting as I had read.
Very dissappointed to find the oil leak.
I also noticed that on braking downhill I could get the forks to bottom out with a harsh sound and feel, like metal to metal impact.
They were rebuilt as std, with the reccommended oil and level, Marzocchi 35 mm, cant really make it happen when static, it was mostly downhill and both brakes on, hit a pothole and clang!
Any ideas would be appreciated

[blethermaskite]

I would always put a bolt in there.
Cheers,
George

[Scottish888]

cheers George,

I wanted to do that and will now, what was it for?

[Jordan]

Footrest bracket.

[ranton_rambler]

Is anything touching when front end compresses? My home-made mudguard bracket was a “gnat’s” too wide and touched the upper shroud when I first rode it.
On my other drum-braked bike I get a clatter sometimes when I fail to avoid a pothole. I believe it’s the brake plate rattling against the stop on the fork slider.

[Scottish888]

Footrest bracket..good.
I will check over the rest of the front end for looses bits and bobs.
The bike was very original when I got it so still fitted with all the stock items.

Cheers folks

[LaceyDucati]

Hi,

Wipe the bottom of the engine dry and oil free, lean the bike to the left, leave it and observe. More often or not it is the strainer sealing washer. It is often difficult to tell the difference between the seal and centre seam leak. If it is the sump washer it will normally be a slight imperfection in the casing. Often the sealing washer face is out of line to the thread, which can limit the useful sealing face. If it is the seal lean the bike right over the other way and remove the filter and smear a small amount on the cleaned seal and re-tighten the filter.

I would always use an 8mm bolt or stud through the footrest mount if it is not in use. However the leak is unlikely to be from the bottom of the sump due to the bolt being absent. The M6 screws should span the lower face without issue. The M8 bolt will however add rigidity of the assembly and without the bolt the oil could potentially track down the hole.

Good luck!

Regards Nigel

[LaceyDucati]

PS. You could add slightly more oil to the forks as that will add progression to the springing via air pressure building up on compression. However 1970's suspension has limited capability against large pot holes.....

Nigel

[Scottish888]

Thank you all for the helpful replies,
I tightened up the crankcase bolts that I could access a wee bit more, I only run the bike for 20 mins to check the engine running there was hardly any leaking this time. Will try Nigel's idea then take it for a much longer run...when I can get it to go beyond 4500 rpm.
Even on the short run I managed to bottom out the forks just under braking, hit a little bump then clang.
Speed hump unbraked at 20mph same result, really feels like the springs are far too soft. Will try the fork oil top up to aid compression.

Thanks again for the good tips

[LaceyDucati]

Maybe worth removing the springs and taking some dimensions for comparison, just in case they have been swapped.

I would add that sometimes you can get clonks with these type forks without locknuts on the stem or if there is any wear on the stem etc. I would also check the head bearings haven't shaken loose. Straddle the bike and bump the front wheel against a wall whilst holding the top cup and cone in your hand to feel for movement. Then tighten slowly until the play disappears.

Nigel