Based on your description and the picture you really may be lucky, and may have done the right thing.

It's really possibly the belt just jumped a tooth or two. This generally wouldn't result in any internal damage, but would keep the bike from running because valve timing would be off. I also suggest pulling the plugs, and turning the motor over slowly by hand to see if you encounter any interference.

Still sorry to hear about it, keep us informed.

Justin

Quote from: A.duc.H.duc. on August 25, 2008, 04:47:15 AM
Based on your description and the picture you really may be lucky, and may have done the right thing.

It's really possibly the belt just jumped a tooth or two. This generally wouldn't result in any internal damage, but would keep the bike from running because valve timing would be off. I also suggest pulling the plugs, and turning the motor over slowly by hand to see if you encounter any interference.

Still sorry to hear about it, keep us informed.

Justin

I have to disagree.

Two teeth off on a Duc generally does damage things from the few I've seen.

Quote from: A.duc.H.duc. on August 25, 2008, 04:47:15 AM
Based on your description and the picture you really may be lucky, and may have done the right thing.

It's really possibly the belt just jumped a tooth or two. This generally wouldn't result in any internal damage, but would keep the bike from running because valve timing would be off. I also suggest pulling the plugs, and turning the motor over slowly by hand to see if you encounter any interference.

Still sorry to hear about it, keep us informed.

Justin

We run interference engines so its possible that the piston hit the valve depending on where the piston was at. On non interference engines you can strip belts all day, the pistons arent anywhere near the valves.

Bad news...   pulled the plugs, put it in 3rd, moved the rear wheel.... very hard to turn, but it doesn't sound good.  turned a bit then stopped dead.

I looked at the forward head, the timing marks don't line up.  Uh, that would be bad...   how do i know exactly how bad this is?

here's some evidence:



http://s249.photobucket.com/albums/gg216/mikesixtysix/blackfog/?action=view&current=08-25-08_1229.flv

Ouch, sorry.  The thud was all the info you need.  Time for exploratory surgury. 

I can't remember where the timing marks are, and it's hard to tell on the exhaust cam in the pic.

Is the exhaust cam mark on the head at 4 o'clock or 6 o'clock in the pic?

If it's at 6, you're fine...

If it's 4, then that sucks.

Oh, and where is the timing mark sitting on the drive pulley?

It's visible there, sort of.  in the pic above, the mark on the top pulley is at 7 o'clock, the mark on the bottom pulley is at 2 o'clock.  on the drive pulley it's also at 2 o'clock.

Quote from: Magnus on August 25, 2008, 10:18:06 AM
It's visible there, sort of.  in the pic above, the mark on the top pulley is at 7 o'clock, the mark on the bottom pulley is at 2 o'clock.  on the drive pulley it's also at 2 o'clock.

Right, but where is the mark on the head?

On the intake cam, the marks are roughly 7 teeth from lining up.

How many teeth off are the marks on the exhaust cam?

ah, now i understand...   please, talk to me like i'm a 4 year old, i don't know jack about this.   

the exhaust cam is the lower one, correct?  it's also i'd say 7 teeth before the mark on the head. 

Quote from: Magnus on August 25, 2008, 10:39:29 AM
ah, now i understand...   please, talk to me like i'm a 4 year old, i don't know jack about this.   

the exhaust cam is the lower one, correct?  it's also i'd say 7 teeth before the mark on the head. 

Yeah, the exhaust cam is the bottom one.  If the timing marks on the two cams are the same number of teeth away from the timing marks on the head (in the same rotational direction) then that's good.

Now look at the timing mark on the drive pulley and see how many teeth it is away from the timing mark on the motor.

I think it's time to schedule a Dr's appointment for BlackFog and bring him in for an examination and hopefully just minor surgery.

Look at the pulleys as well and see if there is any evidence of rock damage (pits or dents).  Something caused the belt to jump and also at the same time cut the belt itself.  Usually the evidence can be identified once you look closely.

Exposed belts are definitely cool but sometimes there is this kind of damage that results thereof. I've experienced the same but still run open belts to this day.

Hopefully it's nothing more major than a few bent valves and that the piston / valve guides are ok.

QuoteExposed belts are definitely cool but sometimes there is this kind of damage that results thereof. I've experienced the same but still run open belts to this day.

You must really really like open belts very much.

Magnus, it couldn't hurt to open up your valve covers and take a look.   

Quote from: uclabiker06 on August 25, 2008, 12:04:58 PM
Magnus, it couldn't hurt to open up your valve covers and take a look.   

Dude... he's already posted pics of his motor with the covers off...


btw, I'm well aware that Duc motors are interference design, I've just not had a belt skip on me, and my general experience has been that one or two teeth has not been enough to cause the interference.

In other words, it would depend on how tight the valve to piston clearence tolerances are.

Quote from: A.duc.H.duc. on August 25, 2008, 01:12:53 PM
Dude... he's already posted pics of his motor with the covers off...

No, he posted a pic with no belt covers.  He hasn't taken the valve covers off yet.