Hello Dicati Forum Members!
I own a 2003 Ducati Monster M750 with approximately 800 miles. It has been sitting for two years, and I'm currently trying to get it back on the road. I installed a new battery and spark plugs, but it struggled to start initially. Eventually, the engine fired up, but I immediately heard a sensation of something "coming loose" internally, and the engine suddenly seized/stuck. It will no longer turn over. I've attached a photo and video for reference—any insight into what might be wrong or how to proceed would be greatly appreciated
Video:
https://youtube.com/shorts/OZR0cOWwetU?feature=share
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Hello,
This is the new link. I updated my post with the new link as well
https://youtube.com/shorts/OZR0cOWwetU?feature=share
Update: I have a new development. I removed the spark plugs to investigate, and this is what I found with one of them (keep in mind, this was a brand-new plug). This suggests something physically struck the plug inside the combustion chamber.
What do you think?
https://youtube.com/shorts/-_nz2HxV2q8?feature=share
I hope it's not that bad!
Your diagnosis of something hitting the plug is spot on. The cylinder head will need to come off.
Before that, pull the belt covers. I think one broke, a valve hit the piston, then broke, stopping any further rotation.
You can do a bunch of messing around, but the basic fact is that head has to come off.
What should I see when the Cylinder head comes off? What else do you suggest doing to finalize a full diagnosis of the problem?
Flounder, thank you for your help. By the way!
I believe you're going to see a broken valve, with some possible damage to the top of the piston and combustion chamber in the head. It's also possible there's some scoring on the cylinder wall. Let's hope that the damage is minor and you don't have to dig deeper.
I had a similar circumstance several years ago, although mine didn't lock up as the valves just bent on a race motor from an over rev.
Get the head off, take some images, and the guys here will be able to give you some choices regarding the best course of action.
Flounder, thank you. I'm going to pull the cylinder head and hope for minimal damage. I'll upload more videos once I have it off.
In the meantime, does anyone else have a different perspective or anything to add? I'd appreciate any extra insight to ensure I have a complete diagnosis before I dive in.
It's really difficult to know. I think people are waiting for more info...like images.
One thing is certain. There's something in that cylinder that doesn't belong.
Ooops - not so good - sorry for you and the bike.
You will need more luck than usual for the piston not to be damaged. If/when the piston hit that plug it could very easily end up hurting parts behind/under it ( = seized engine? )
New plugs; which plugs are they? (maybe too long?)
Quote from: stopintime on March 24, 2026, 11:27:13 AMOoops - not so good - sorry for you and the bike.
You will need more luck than usual for the piston not to be damaged. If/when the piston hit that plug it could very easily end up hurting parts behind/under it ( = seized engine? )
New plugs; which plugs are they? (maybe too long?)
I'd agree that maybe plugs too long, but he said it started and ran...then got noisy and stopped. If the plugs were too long it would have locked up on cranking...no?
Maybe. Maybe not. The ugly sound was immediate.
Heads off [thumbsup]
If this bike is loved, now is an opportunity to make it perfect. (And for us to enjoy the story and photos of the repair)
Most likely snapped timing belt(s)
What plugs are they (looks too long)?
New update: The timing belt is intact and appears to be in good condition. Here is the video:
https://youtube.com/shorts/bVtvMjHaBsM?feature=share
The next step is to pull the cylinder head to see what's happening inside.
Regarding the spark plugs: I went to AutoZone, and they recommended the NGK DCPR8E based on my bike's year, make, and model. Previously, I was running Champion RA6HC. Do you think the cross-reference could be the issue? I suspect a piece of the broken plug may have dropped into the cylinder and caused the obstruction/damage.
Both plugs should be ok and the two sites I checked for "reach" (thread length it seems) list 19mm on both. So, probably correct plugs (even if that doesn't helpp you much...)
Those are the correct plugs. If they were too long, both plugs would have been damaged by contact with the piston...No?
Fortunately, I only needed to replace the plug on the vertical cylinder, which was the only one showing impact damage. What internal issues would cause contact with the spark plug?
As mentioned 1;
belts - if it jumped a tooth or two a valve could suddenly be where it shouldn't
As mentioned 2;
a bent valve (seized?) might also suddenly be where it shouldn't
Which leads back to "As mentioned 3" - heads off and pray [thumbsup] , and please remember to take pictures and to share them.
I'm going to stand fast that you need to pull that head.
Or just send it to be recycled.
Quote from: ducpainter on March 24, 2026, 10:24:45 AMOne thing is certain. There's something in that cylinder that doesn't belong.
+1 You need to look inside and show some images.
Quote from: ducpainter on March 25, 2026, 04:22:33 PMI'm going to stand fast that you need to pull that head.
There's no way around it.
take the belt covers off and im sure one belt has snapped , causing the piston to hit the valves,
Quote from: jerryz on March 27, 2026, 04:51:25 AMtake the belt covers off and im sure one belt has snapped , causing the piston to hit the valves,
Quote from: Juanchojt on March 25, 2026, 06:48:42 AMNew update: The timing belt is intact and appears to be in good condition. Here is the video:
https://youtube.com/shorts/bVtvMjHaBsM?feature=share
The next step is to pull the cylinder head to see what's happening inside.
Regarding the spark plugs: I went to AutoZone, and they recommended the NGK DCPR8E based on my bike's year, make, and model. Previously, I was running Champion RA6HC. Do you think the cross-reference could be the issue? I suspect a piece of the broken plug may have dropped into the cylinder and caused the obstruction/damage.
He already did that Jerry, and the belt is intact.
Any updates?
Was thinking the same thing. Be beneficial for the community to know an outcome. It archive's collective experience
+1.
I`m wondrin how a snapped belt could damage a plug like here?
Usually only causes piston and valve to meet or?
Quote from: greenmonster on April 01, 2026, 03:12:29 AM+1.
I`m wondrin how a snapped belt could damage a plug like here?
Usually only causes piston and valve to meet or?
The belt didn't snap. It might have jumped teeth.
Quote from: Juanchojt on March 25, 2026, 06:48:42 AMNew update: The timing belt is intact and appears to be in good condition. Here is the video:
https://youtube.com/shorts/bVtvMjHaBsM?feature=share
The next step is to pull the cylinder head to see what's happening inside.
Regarding the spark plugs: I went to AutoZone, and they recommended the NGK DCPR8E based on my bike's year, make, and model. Previously, I was running Champion RA6HC. Do you think the cross-reference could be the issue? I suspect a piece of the broken plug may have dropped into the cylinder and caused the obstruction/damage.
Both plug models were ok [thumbsup]
OK; refrasing:
Some have suggested broken belt. Probably din not happend here as picture show vertical is OK.
Besides this topics engine, can a broken belt damage a plug as bad as we`ve seen here?
Quote from: greenmonster on April 02, 2026, 03:44:30 AMOK; refrasing:
Some have suggested broken belt. Probably din not happend here as picture show vertical is OK.
Besides this topics engine, can a broken belt damage a plug as bad as we`ve seen here?
The way I see it...Only if a valve breaks, and the head of it is floating around in the cylinder.
I really wish that people would come back and update...even if they decided to just sell the bike as is, or replace the motor rather than investigate.
I've pmed the dude asking for an update. [popcorn]