Cam belt one tooth out?

24-12-2018, 11:41 AM

I've just had a frustrating couple of days with my 796. For the second time I have fitted new can belts, no problem done this before. After that a new set of starter cables (both from Exact Fit).

The problem now is that it is not very happy, it will fire up but is running very lumpy and will not tick over. The plugs are coming out back with fuel.

I did lock the cams in position with 6mm Drill bits to stop them moving once I had rotated the rear wheel to reach TDC, but has something moved?

I'm not sure the horizontal cylinder may be one tooth out, the alignment looks wrong.

Had any one got any ideas?

Mossleymonster · 24-12-2018, 12:15 PM

Did you mark the old belts and count the teeth?

24-12-2018, 02:48 PM

I've just re-checked it all. Moved both cams in to position using the rear wheel and I find that the crank pulley is not lined up to the mark on the crankcase.

So take both belts back off and move the crank pulley into the correct position, check the cam pulleys have not moved and re-fit the belts. Check the tension etc and fire it back up.

Sounds like it's only running on one now even worse than before!

maxxjod · 24-12-2018, 03:48 PM

If it's now sounding like it's only running on one cylinder is it possible you are 180 out on one of the cylinder's? I can't remember if you can do it on a Ducati L twin, I know that you can on an aprilia V twin.

utopia · 24-12-2018, 04:20 PM

Before I start mine up after a belt change I always rotate the engine (in the direction it runs) by a couple of cycles, before re-aligning the pulley marks to check that all is as it should be.
Did you do that ?

Mossleymonster · 24-12-2018, 04:42 PM

Quote:

Originally Posted by maxxjod

If it's now sounding like it's only running on one cylinder is it possible you are 180 out on one of the cylinder's? I can't remember if you can do it on a Ducati L twin, I know that you can on an aprilia V twin.

This makes sense.

Not that I'm Questioning Utopia.

Luddite · 24-12-2018, 04:59 PM

I'm assuming that the 796 parts are the same as my Evo.

When you locked the camshafts, did you lock both at the same time or just one? The belts should be changed with the horizontal cylinder at TDC. If you lock both cams, then the locking pins will only locate in their holes when the motor is in the correct position - if only one pin is used, then the motor could be in the wrong position.

Also, even if you lock both cams, if you don't also lock the crankshaft, there's a possibility that you might accidentally move the crank out of position when refitting the belts.

Finally, when tensioning the belts, (and while both cams are locked), you need to loosen the three torx bolts (no. 4 in the diagram) on each cam pulley so that you can correctly tension the belt run opposite the moveable tensioner.

As you can see from the diagram, the pulleys themselves are slotted and can rotate slightly independently of the cams so that you can evenly tension both sides of the belt, (without affecting the cam timing). If you don't do this, then you are effectively only able to adjust the tension of the side running against the moving tensioner.

When finished, tighten the torx bolts up to 10Nm.

What utopia says is very good practice - any time you disturb the belts, it's wise to rotate the engine a few times by hand (plugs out) to ensure there's no contact between valves and piston.

Mossleymonster · 24-12-2018, 05:07 PM

I'm gettin the willy's now. My first ever cam belt change next week.

Encyclopaedia Ludditica frightens me....... In a nice way. I should know more, but I don't.

24-12-2018, 06:52 PM

When I looked at the belts today today I locked both cam pulleys, I then saw that the crank pulley was not lined up with the mark so I removed both belts and moved the crank pulley so it lined up.

But I had tightened up the slip bolts on the cam pulleys before doing the tension. I'll take another look on Wednesday when I get the chance.

I'm being to wonder if I have bent a valve or something similar. Is it possible to tell by eye?

Mossleymonster · 24-12-2018, 07:58 PM

One wonders...

Luddite · 24-12-2018, 08:29 PM

I don't know whether you could visually detect a bend but I bought a cheap endoscope from Lidl last year, which allows you to look inside the motor. I'd guess if you pushed the camera down the plug'ole, you'd be able to see if there was any evidence of the valves hitting the top of the piston.

Also, as there are only very weak closing springs in the valve train, you can turn the camshafts by hand (with belts removed). If you placed the cylinder at BDC and then turned the camshaft by hand, I would think a bent valve stem would be felt as an unusual tightness.

If you're worried your cams are in the wrong position, check them by setting the horizontal cylinder at TDC on the power stroke (the crankshaft mark on the drive pulley will line up with the one on the clutch cover). If you then turn the camshafts until you can insert the locking tools, you know they are in the right position. And, as utopia said, whenever you've disturbed the cams, ALWAYS turn over the motor a few times by hand to ensure everything's spinning freely.

Hope you get this sorted quickly.

Luddite · 24-12-2018, 08:42 PM

Quote:

Originally Posted by Mossleymonster

I'm gettin the willy's now. My first ever cam belt change next week.

No need to get paranoid! As long as you lock your cams in position and don't move the crankshaft (easily checked with the alignment marks) you'll be fine. If you don't have the proper pins, a couple of 6mm drill bits will do the job (held in with masking tape). As I mentioned earlier, they will only both engage when the motor is in the correct position (horizontal cylinder at TDC on the power stroke). Using a torch, you can see where the pins locate through the access hole.

Just remember to remove the pins before you try to turn over the motor!

Mossleymonster · 24-12-2018, 09:06 PM

Quote:

Originally Posted by Luddite

No need to get paranoid! As long as you lock your cams in position and don't move the crankshaft (easily checked with the alignment marks) you'll be fine. If you don't have the proper pins, a couple of 6mm drill bits will do the job (held in with masking tape). As I mentioned earlier, they will only both engage when the motor is in the correct position (horizontal cylinder at TDC on the power stroke). Using a torch, you can see where the pins locate through the access hole.

Just remember to remove the pins before you try to turn over the motor!

I'm not paranoid yet, the drugs don't work this early.

Luddite · 24-12-2018, 09:55 PM

Quote:

Originally Posted by Mossleymonster

I'm gettin the willy's now. My first ever cam belt change next week.

If you want to borrow my locking pins, I'd be happy to pop them into a jiffy bag and send them off to you - no charge. Just PM me your address.

25-12-2018, 08:39 AM

I'll spend some time tomorrow going back to square one. I'm sure I have carried out the correct sequence of events but something somewhere must have moved.

I had locked the cams with Drill bits, checked the belt tension and then turned the engine over by hand before starting.

Fingers crossed nothing is bent, I commute daily on the Monster!

24-12-2018, 11:41 AM	#1
alickswud Guest Posts: n/a	Cam belt one tooth out? I've just had a frustrating couple of days with my 796. For the second time I have fitted new can belts, no problem done this before. After that a new set of starter cables (both from Exact Fit). The problem now is that it is not very happy, it will fire up but is running very lumpy and will not tick over. The plugs are coming out back with fuel. I did lock the cams in position with 6mm Drill bits to stop them moving once I had rotated the rear wheel to reach TDC, but has something moved? I'm not sure the horizontal cylinder may be one tooth out, the alignment looks wrong. Had any one got any ideas? Last edited by alickswud; 24-12-2018 at 01:09 PM..

24-12-2018, 12:15 PM	#2
Mossleymonster Registered User Join Date: Nov 2017 Location: Barnsley Bike: M1100s Posts: 238	Did you mark the old belts and count the teeth? __________________ Always remember. Your home is at risk if you set fire to it.

24-12-2018, 05:07 PM	#8
Mossleymonster Registered User Join Date: Nov 2017 Location: Barnsley Bike: M1100s Posts: 238	I'm gettin the willy's now. My first ever cam belt change next week. Encyclopaedia Ludditica frightens me....... In a nice way. I should know more, but I don't. __________________ Always remember. Your home is at risk if you set fire to it. Last edited by Mossleymonster; 24-12-2018 at 05:17 PM..

24-12-2018, 07:58 PM	#10
Mossleymonster Registered User Join Date: Nov 2017 Location: Barnsley Bike: M1100s Posts: 238	One wonders... __________________ Always remember. Your home is at risk if you set fire to it.

25-12-2018, 08:39 AM	#15
alickswud Guest Posts: n/a	I'll spend some time tomorrow going back to square one. I'm sure I have carried out the correct sequence of events but something somewhere must have moved. I had locked the cams with Drill bits, checked the belt tension and then turned the engine over by hand before starting. Fingers crossed nothing is bent, I commute daily on the Monster! Last edited by alickswud; 25-12-2018 at 08:41 AM..

24-12-2018, 02:48 PM	#3
alickswud Guest Posts: n/a	I've just re-checked it all. Moved both cams in to position using the rear wheel and I find that the crank pulley is not lined up to the mark on the crankcase. So take both belts back off and move the crank pulley into the correct position, check the cam pulleys have not moved and re-fit the belts. Check the tension etc and fire it back up. Sounds like it's only running on one now even worse than before!

24-12-2018, 03:48 PM	#4
maxxjod Member Join Date: Feb 2009 Location: Brighton Bike: M750 Posts: 146	If it's now sounding like it's only running on one cylinder is it possible you are 180 out on one of the cylinder's? I can't remember if you can do it on a Ducati L twin, I know that you can on an aprilia V twin.

24-12-2018, 04:20 PM	#5
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	Before I start mine up after a belt change I always rotate the engine (in the direction it runs) by a couple of cycles, before re-aligning the pulley marks to check that all is as it should be. Did you do that ?

24-12-2018, 04:59 PM	#7
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	I'm assuming that the 796 parts are the same as my Evo. When you locked the camshafts, did you lock both at the same time or just one? The belts should be changed with the horizontal cylinder at TDC. If you lock both cams, then the locking pins will only locate in their holes when the motor is in the correct position - if only one pin is used, then the motor could be in the wrong position. Also, even if you lock both cams, if you don't also lock the crankshaft, there's a possibility that you might accidentally move the crank out of position when refitting the belts. Finally, when tensioning the belts, (and while both cams are locked), you need to loosen the three torx bolts (no. 4 in the diagram) on each cam pulley so that you can correctly tension the belt run opposite the moveable tensioner. As you can see from the diagram, the pulleys themselves are slotted and can rotate slightly independently of the cams so that you can evenly tension both sides of the belt, (without affecting the cam timing). If you don't do this, then you are effectively only able to adjust the tension of the side running against the moving tensioner. When finished, tighten the torx bolts up to 10Nm. What utopia says is very good practice - any time you disturb the belts, it's wise to rotate the engine a few times by hand (plugs out) to ensure there's no contact between valves and piston.

24-12-2018, 06:52 PM	#9
alickswud Guest Posts: n/a	When I looked at the belts today today I locked both cam pulleys, I then saw that the crank pulley was not lined up with the mark so I removed both belts and moved the crank pulley so it lined up. But I had tightened up the slip bolts on the cam pulleys before doing the tension. I'll take another look on Wednesday when I get the chance. I'm being to wonder if I have bent a valve or something similar. Is it possible to tell by eye?

24-12-2018, 08:29 PM	#11
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	I don't know whether you could visually detect a bend but I bought a cheap endoscope from Lidl last year, which allows you to look inside the motor. I'd guess if you pushed the camera down the plug'ole, you'd be able to see if there was any evidence of the valves hitting the top of the piston. Also, as there are only very weak closing springs in the valve train, you can turn the camshafts by hand (with belts removed). If you placed the cylinder at BDC and then turned the camshaft by hand, I would think a bent valve stem would be felt as an unusual tightness. If you're worried your cams are in the wrong position, check them by setting the horizontal cylinder at TDC on the power stroke (the crankshaft mark on the drive pulley will line up with the one on the clutch cover). If you then turn the camshafts until you can insert the locking tools, you know they are in the right position. And, as utopia said, whenever you've disturbed the cams, ALWAYS turn over the motor a few times by hand to ensure everything's spinning freely. Hope you get this sorted quickly.