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Discussion Starter · #41 · (Edited)
The hits just keep on coming with this thing.

In the annoying category... who puts two different types of sealing washers on a brake fitting? I don't mean aluminum on one side and copper on the other, I mean aluminum on both sides with a copper thrown in for good measure?


And... Valve adjustments. Ducatis get a bad rap for how complicated the valvetrain is. Well it's really not, especially the two valve stuff.


I considered not even checking these because the top end was supposedly recently done, and... to be honest... I was afraid of what I might find. But it had to be done so today I checked them.

Oh FFS. The last guy to work on this didn't know and/or care what the fook he was doing.

Typical max clearances for a 900ss are
Intake opener 0.10mm
Exhaust opener 0.12mm
Both closers 0.02mm

I measured 3 of the 4 valves (because you have to pull the shock to get to the last one)
Horizontal cylinder
Intake
Opener 0.15 (0.10max)
Closer 0.23 (0.02 max)
Exhaust
Opener 0.15
Closer 0.00 Ducati does spec 0.00 as the lower limit, but no one has a 0.00 feeler gauge so it becomes a matter of feel. This one felt tight to me so 0.00 is a questionable result... it may be binding.

Vertical cylinder
Intake
Opener 0.46
Closer 0.15

TL;DR, the clearances are all over and so far out of spec that there is no way they were ever right. They were so far out I checked everything multiple times to make sure I wasn't just being stupid. And this isn't my first time doing this.

Is it any wonder the bike was so hard to start and didn't run all that well? Between the play in the countershaft and the way off valve settings, just how much faith should I have that the crank has the right preload? I'm a pretty trusting guy but there is a limit.

In other news... I tried to contact the guy with the cheap 748 and got no reply, so that looks like a dead end. Which sucks cuz I figured out how to pay for it and if it were available I'd probably bail on this and make that the trackbike for next year. I should have some 916 cases showing up tomorrow so I could get started on an air cooled engine for it right away.

I'm going to try to contact 748 guy again. If I'm going all in on an engine rebuild, it'd be cool if I had that worked out before I got started. If a 748 shows up, the 900 becomes a parts bike for the engine build.

I knew this bike might end up getting used for parts but this is the first time I've come across a Ducati that has had such poor work done to it previously.
 

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I had to check the valve clearances a few weeks ago. First time that I've had to do it, and as you say not too difficult.
Wouldn't fancy having to adjust them although Brad says it's easy.
This is checking clearances according to my manual.
Inlet opening 0.05 to 0.12mm
Inlet closing 0.03 to 0.20mm
Exhaust opening 0.05 to 0.15mm
Exhaust closing 0.03 to 0.20mm

Btw also found some evidence of a chain break.
 

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Discussion Starter · #43 ·
I'm using an old Ducati factory manual and I seem to recall Ducati changed the clearances at some point but those closing clearances sound pretty large? If the closers get too loose, the collets get broken. Today I found two broken collets on the inlet valve with the largest clearance - 0.23mm. Two other closers had zero clearance, at least one seemed too tight, and those shims are noticably shinier where the collets sit than on the other closers. I ended up ordering six shims and the the other two will be a lapped to open them up.

Anyway... you know your shop is too dirty when you decide to build a brace to hold the frame up instead of digging out the engine hoist to hold it up. Yep, that was me today. Granted the brace is more solid than hanging it from a hoist but tomorrow is cleaning day.

I also found the ad for the cheap 748 I was looking into has been deleted, so that one is a no go. The cases are supposed to show up tomorrow and I'm still going to proceed putting an engine together, at least as far as I can with what I have. Something else will come along at some point.
 

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closing specs have been 0.03 to 0.05mm, with a limit of 0.20mm since 93.

prior to that, they were 0.00 - 0.02mm in all the manuals from f1 to 91 models that i have.

you check for binding by turning the cams. just the easiest check there is.
 

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Discussion Starter · #45 ·
I've seen those specs in a Haynes manual, but the Duc service manual I started with has the old numbers. It seems wrong to open the spec up from 0.02 to 0.20, and the one valve that had a closer near that had broken collets, so I'm trying to get nearer the original specs. I'm also trying to keep in mind just how fooking small 0.02mm really is when I end up with an intake opener at 0.12 instead of the 0.10 max I wanted. Yes, I'm leaving that one as is. FFS I'm fooling myself thinking I can measure it that accurately anyway, considering I don't have feeler gauges in .01mm increments! In the end it all comes down to feel, doesn't it?

After some confusion measuring closing shims I'm at the point of re-ordering a couple and then I should be done. I ended up lapping the two closers that had no clearance (and did bind) and got them to where I can't measure any clearance but also can't feel any binding. I took something like .02mm off one to make it work. The other took more like .08 to get there.

One hassle was I wrote down the size of my closer tools wrong, so had the wrong dimensions for the shims. It didn't matter since they all had the same error and I was only looking for the difference between them. That fell apart when ordering replacements though. The openers matched what I expected, but the closers... oops. One of the two worked in a different spot. I'm now using a different set up with electronic tools where I can zero out the length of the tool and read the size directly instead of doing math each time... that's what I get for using old school tools so I didn't have to deal with batteries going dead.

It's been a long time since I've done this. I learn a thing or two each time, and this time the big lesson was in a video you did that showed the simple tool you use to hold the closing rocker down. Fack me, why the heck isn't this more well known? I used an 8mm allen wrench first but it was too long so I turned something up on the lathe. I made it shorter than I should have but it works. And it makes putting the collets back in place SO much easier... so thanks for that idea!
 

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i think the 0.20mm is code for "don't worry about it to save time and money". at 0.20mm they'll idle badly.

i do it only by feel, and you can feel 0.02 pushing on the end of the valve. it's really a pretty simple job all round. as you found, measuring tools can be one of the biggest hassles.
 

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Discussion Starter · #49 ·
It's not all that important really. As long as there's no drag and the clearance isn't too big, it's good.

I figured out I can get there without ordering any more shims, so I've got that going for me. I thought I had it nailed today but the last closer has just a touch of drag on it still and I ran out of time. I'll fix tomorrow and then decide if I'm ok with two openers being at the upper limit. Three of the closers will be at zero from what I can tell, the last will be around .04mm. In any case it should be better than when I started.

Also forgot to mention, the package from the guy who sold me the 916 cases showed up. It fit in the mailbox so I knew right away something was up. Turns out he sent me a used Chevy emblem off the back of an Equinox. WTF? The good news is he refunded my money with zero hassle but I'm bummed I didn't get the case!

I still want to find a 748 but it's back burner again.
 
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