Valve clearance

[pear0]

Having trouble determining the proper valve clearance for the 250 engine that I have. # is 85278 and it has non adjustable rockers and 4 ring piston. Current reading for intake and exhaust is .009 in. Is this OK? If not OK is the a place to get proper buckets. I assume that grinding them down is not a good idea..
The bike that this engine came to me in is a scrambler but I thought that the 4 ring piston was in touring models. Thanks for any light you can shine on my ignorance . Tom

[Bevel bob]

Hi, Where in the world are you?.Buckets,lash caps,shims are availiable from many sources. You will need a cheap micrometer to work out what you have and from that what you need. Openning shims from some later Ducati twins will also fit , I think yours are the 8mm range . 9 thou is more than it should be, but it will still run.Rubbing down the shims will give more clearance. The motor could be in just about any state of tune,to spec the motor you will need to post photo's of the piston, measure valve sizes,carb size,cam details etc. It is more likely that the motor is in a modest tune if it has a 4 ring piston. Shim requirements will change if you do any work on the valves and seats.Lacey Engineering will send you what you need.My guess is that the motor is from around 1962/3.The frame numbers will not match.

[double diamond]

The original equipment 250 scrambler piston is a four ring cast piston similar to the touring models but with higher compression (9.5:1 as I recall). Only the 250 sports models had three ring forged pistons.

[pear0]

Good advice Thanks. I am in Montana. I post on bevelheads as TomA.
The engine was modified with rocker box drain hoses direct to crankcase using pipe thread fittings cross threaded into the M10 x 1 threads on the drain ports.
But what is the correct clearance . Or is it necessary to know the mods before saying. .
This is my first Ducati single since I bought one in 59. I will get some pictures Tom

[Bevel bob]

The extra drains are good,and may mean the motor is modified for higher performance.different cams need different clearances.If noisy I would try 5 and 7 thou.But best to get the cam identified from the timing figures. (not as easy as it sounds).

[double diamond]

According to the factory manual, valve clearance for stock cams are: Scrambler .15mm in, .20mm ex, Diana MkIII: .20mm in, .30mm ex, Mach 1/Mk3: .15mm in, .30mm ex. You may be able to identify your cam by removing the bevel cover and looking for the color code painted on the end of the cam (where it is fastened to the cam bevel gear). Scrambler cams have a white paint mark, Diana is red, Mk3 is grey. I'd say you have a 50/50 chance that the paint is still on the cam. Megacycle recommends .005"-.006" in and .007"-.008" ex for their race cams so about the same as the scrambler clearance. You can also take the cam bearing cap off and have a look at the profile of the cam. If the lobes appear to be symmetrical, it's likely a stock scrambler cam. If the lobes are asymmetrical, could be a Mk3 cam. BTW, I had the compression ratio wrong in my previous post, the manual calls out 9.2:1 for the scrambler. I've also heard that Alfa Romeo winkle caps will work on Ducati singles for valve clearance adjustment if you have a source for them. Matt

[pear0]

There is a small piece of paint on the end of the cam which appears to be yellow so I assume was originally white and the lobes appear symmetrical which would reenforce that it is stock. So I am looking for .15 intake and .20 exhaust.
I do have access to Alfa stuff. I gave my 59/60 Giulietta(which I bought new) to my son in law . He said that he wanted to restore it. He has been accumulating parts for it for 12+ years now. He should either have some buckets or know where to get them.
I will get hold of a micrometer and make a spring compressor and get to work. Thanks for the good advice . Tom

[Eldert]

Hi Tom

Alfa s have winkle caps for 9 mm valve stems . only the twin spark has 8 mm valve stems and winkle caps .

the Ducati Pantah range all use the 8 mm winkle caps as the Ducati singles do .

Eldert

[pear0]

Thanks Eldert. I will chase some down on the internet.. Tom