belts , timing and valves - damage ???

drew23 · February 02, 2011, 08:13:54 PM

first post ,,, great site . the bike is an 01 ,750M , carbed . it's been parked for a few years , so this was the winter i've got around to getting it running , with hopes of vast enjoyment this spring . went through the standard fix-its and such ,,, tire , battery , lights ,signals , oil change , carb(s) rebuild ect.,,,, and it was running rather well ,- only at idle and through the revs ,,, haven't gotten that far yet ( ridability

. so obviously the belts needed inspection . loosened the belts , inspected - good , replaced and set tension . at that time didn't notice that the vertical cylinder timing mark was off , so , hence the "sound"

when started . didn't run again and learned that a tension spring moved the alignment ,,,, loosened belt(s) , manually brought back into alignment with other marks ( crankcase , horizontal cylinder ) . Afterwards,- in gear , plugs out , turns freely by hand and running , slightly noticeable . Really just seeking knowledgeable advice on next course of action . Thanx A. Little

bigiain · February 02, 2011, 09:18:53 PM

I'd do a compression and/or leak down test - that'll tell you if you've bent a valve - or at least it'll tell you when you've bent it far enough to make it not seat properly.

I probably wouldn't take it to the track and go hard straight away just on the basis of a compression test, it's possible you've touched it softly enough that if doesn't leak in a static(ish) test, but weakened it enough that it'll let go when you downshift a little early and spin it up towards 9k rpm...

If you were only one tooth out and ran it gently enough that it just went "tap tap tap" you might be lucky and get away with it. If it went "clunk clunk clunk" (or worse, "graunch stop!") you might want to start taking that head off and save up for new guides and valves...

Big

drew23 · February 02, 2011, 09:27:33 PM

that i will do ,,- question about the " downshift early , and let go at 9k " part ,,,, that has me nervous . thanx

Turf · February 02, 2011, 09:45:54 PM

...dude, less caffeine

anything more than a tooth and odds are you're screwed

drew23 · February 03, 2011, 11:17:11 AM

well , yeah , thats my concern . there's still work to be done to , so it's not like it's keeping me from riding . but this being my first Duc i'm learning as i go ,- so messing with the valves , possibly having to remove the head ,,, any adjustments or corrections that can be done , is what i'm looking at/for . not knowing there was spring tension on the vert. cylinder is what caused the problem to begin with . so i just want to be careful and not damage anything any further . ( as to previous post - "screwed" ,,,?

a bit more specific )

ducpainter · February 03, 2011, 12:27:26 PM

Quote from: drew23 on February 03, 2011, 11:17:11 AM
well , yeah , thats my concern . there's still work to be done to , so it's not like it's keeping me from riding . but this being my first Duc i'm learning as i go ,- so messing with the valves , possibly having to remove the head ,,, any adjustments or corrections that can be done , is what i'm looking at/for . not knowing there was spring tension on the vert. cylinder is what caused the problem to begin with . so i just want to be careful and not damage anything any further . ( as to previous post - "screwed" ,,,? a bit more specific )

He's saying you more than likely bent a valve, or both. It's also not uncommon for the valve guides to crack when a valve bends.

Before you get too crazy, do a leak down or compression test.

drew23 · February 03, 2011, 01:25:43 PM

thnx,- any idea as to optimum cylinder compression ( range ) the bikes got 14,500 on it milage wise ,,, mostly around town . also , the cracked or bent valve guides - can that be done with visual inspection

64duc · February 03, 2011, 01:28:49 PM

And if it sat for several years DO replace the belts or you will likely break one and destroy cylinder, head, and piston.

If you have to replace a valve, you will have the head off anyway, better to just do it. The answer to your question is maybe.

ducpainter · February 03, 2011, 03:24:08 PM

Quote from: drew23 on February 03, 2011, 01:25:43 PM
thnx,- any idea as to optimum cylinder compression ( range ) the bikes got 14,500 on it milage wise ,,, mostly around town . also , the cracked or bent valve guides - can that be done with visual inspection

The cylinders should be within 10% of each other. It's difficult to give a number for what it should be. A leak down test is a better indicator of top end health.

bigiain · February 04, 2011, 04:41:26 PM

Quote from: ducpainter on February 03, 2011, 03:24:08 PM
The cylinders should be within 10% of each other. It's difficult to give a number for what it should be. A leak down test is a better indicator of top end health.

+1 - it's the comparison between the two that you want to look for, not absolute numbers.

Having said that, the 750 motor is the lowest compression motor Ducati have made in about half a century, don't get alarmed if people used to high performance motors tell you to expect ~170psi and you end up seeing something down around 120 or 130. I ink the commpresion ratio is only 9:1, so under perfect conditions you'd only see 135psi.

Big

drew23 · February 04, 2011, 04:59:57 PM

but after the comp. check ,,, what will that indicate and what will be necessary after that . again , what visual inspections can be done and how

?

ducpainter · February 04, 2011, 05:04:40 PM

Quote from: drew23 on February 04, 2011, 04:59:57 PM
but after the comp. check ,,, what will that indicate and what will be necessary after that . again , what visual inspections can be done and how ?

If the cylinder that had the incorrect belt timing is lower than the other by more than 10%...and I suspect it will be much lower... you need to pull that head and inspect the valves and guides, and repair as necessary.

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belts , timing and valves - damage ???