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Mystery mods?
http://www.ducatittandf1.com/viewtopic.php?f=10&t=12254		 Page 1 of 1
Author:  Bull Tahr [ Fri Nov 17, 2023 12:40 am ]
Post subject:  Mystery mods?
While my recently aquired F1 is a street legal "Vanilla" F1, I think that this forum is the best place for this question.
So while going over this bike, I have replace fluids, rubber etc and done a basic clean up fettle, but I have found a few "anomalies" that have me a little stumped. So any advice or ideas would be greatly appreciated!
1. It has been upgraded to adjustable cam pulleys with the round tooth belts, Timing marks all line up as normal but there are a few black marker lines on the crank pulley, which I assume may have helped when they fitted and adjusted the new pulleys.
2. The Vertical cylinder spark plug had a 4mm shim washer on it , none on the Horizontal. Plugs are correct ones. Why? Shim looks like it was machined on purpose, not just a random fat washer that's for sure.

Now I assume, and I not experienced inside engines (Peripherals/ suspension, clutch etc no prob but internals not my thing), that if they put lumpier cams in the adjustable pulleys would have been fitted (Or else why bother?)

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Author:  618F1 [ Sat Nov 18, 2023 10:07 pm ]
Post subject:  Re: Mystery mods?
If you pulled off one of the cam end caps and took a photo of the letters and numbers on that cam and posted it then someone here can ID it. Then you will know if stock or not.

No idea why a 4mm thick washer is needed with stock plugs and pistons. There might be a higher compression piston there without a divot for the plug electrode, or maybe the counterbore for the plug is just cut too deep.

MikeV
Author:  Bull Tahr [ Sun Nov 19, 2023 4:26 pm ]
Post subject:  Re: Mystery mods?
618F1 wrote:
If you pulled off one of the cam end caps and took a photo of the letters and numbers on that cam and posted it then someone here can ID it. Then you will know if stock or not.

No idea why a 4mm thick washer is needed with stock plugs and pistons. There might be a higher compression piston there without a divot for the plug electrode, or maybe the counterbore for the plug is just cut too deep.

MikeV


Thanks Mike, I'll pull and see. As far as the plugs go, I'll try and measure from start of plug holes to top of pistons at TDC and see if there is any difference.
Author:  danomar [ Sun Nov 19, 2023 8:34 pm ]
Post subject:  Re: Mystery mods?
Bull Tahr wrote:
The Vertical cylinder spark plug had a 4mm shim washer on it , none on the Horizontal. Plugs are correct ones. Why?


That might for plug indexing—aiming the electrode for better ignition. I have used 1mm or 2mm washers for indexing in the past, but 4mm thick? Possibly the PO accidentally left it on and forgot..?
Author:  Bull Tahr [ Tue Nov 21, 2023 7:28 pm ]
Post subject:  Re: Mystery mods?
UPDATE: She does indeed have different cams in there, 900SS cams according to the previous owner. The shim on the rear cylinder will stay there for now until I can get the heads off and see what's been going on there. Si t will me a very tender process on cranking by hand once I do the belts and checking as I go that everything turns smoothly as she should....
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