Timing belt tension rollers - how should they feel if they’re OK?

yellowfever · 06-09-2024, 03:26 AM

OK I appreciate checking belt rollers by hand is something of a dark art, acquired through experience. Or a waste of time unless really egregiously worn according to some. And trying to describe how something should ‘feel’ in a post is perhaps even more difficult.

But anyway here goes nothing, any thoughts appreciated!

How freely should they turn? Are new ones stiffer to start with? Background below…

Whilst belts off to investigate oil leak on my 2006 S2R 1000 I’ve been checking the belts and rollers. Belts will be going back on as they look fine at 1.5 years old and I’ll be swapping them for new at big service next year anyway.

On rollers the horizontal fixed and mobile rollers were both replaced in 2016 and the vertical mobile roller was replaced in 2014 and they all feel fine, rotating freely enough without any slop, noises or notchiness.

The vertical fixed roller is still the original from 2006 complete with the weird special 10mm across flats bolt holding it in place. It also has no slop and turns OK but is noticeably stiffer than the others. I had thought I might replace it at some point as it’s the only original roller still left. I’ve been told it may only have been left in situ when the others were changed previously by pro mechanics as it still turns alright and because between the threadlock and weird bolt and difficult access they’re apparently not that easy to remove, so tend to get left in place unless they’ve obviously gone bad.

I’d had the foresight to get a new OEM fixed roller from MSP as I expect I’ll need to replace it at some point. So I thought a useful cross check as I’m new to feeling belt rollers would be to see how freely the new one turned. Surprisingly it’s very stiff - more so than any of the rollers on the engine now including the fixed vertical one that I was thinking of replacing! it’s meant to be Ducati OEM and was €51, though it didn’t come with any Ducati packaging. Anyone got any idea if this is normal? Are new rollers stiffer at first? Or have I got a dodgy part I should return?

Thanks in advance for any thoughts…

Dukedesmo · 06-09-2024, 08:57 AM

Not sure if S2R is the same but on my M900 there is the one 'special' long roller/bearing and the other is just 2 standard bearings fitted together.

The special ones do seem tighter and they are expensive but I've never changed mine as they seem OK.

The others are cheap enough to change every so often, in fact I changed mine a couple of years back as the front cylinder belt was 'tracking' against the edge of the pulley, leaving some rubber dust behind and the bearings did seem a little loose - all good now, at least last time I checked.

yellowfever · 06-09-2024, 03:07 PM

Hi thanks for the reply. My mobile belt tensioner rollers have both been replaced in the past and are both the newer design in one complete piece with one long bearing on the shaft, not the two roller bearings next to each other held on one shaft by a circlip like the originals like you have. Mine have to be replaced as one item and not cheap, but happily they are both fine as is the other (also previously replaced) fixed roller (which always had the longer single bearing design).

The remaining fixed roller is stiffer but still moves smoothly and is not loose so think I’ll be leaving it for now at least given it’s meant to be a pita to remove and the replacement I’ve got is stiffer still!

Still not sure if I’ll return the new one as possibly defective… just don’t know if they all start off that stiff. I have only three data points that make no sense…

Brand new = stiffest
2006 = next stiffest
2016 = least stiff

jerry · 07-09-2024, 02:24 PM

My 1991 750ss rollers at least 16 years and still fine my M750 rollers are 24 year old still feel fine, and the S4 is 23 years old and has had one roller changed .

Dukedesmo · 07-09-2024, 02:33 PM

All those that I have seen (mine plus a couple of spare I have) seem tight compared to conventional bearings, maybe due to the length of the rollers inside?

It's likely they free up a little as they warm up, the only reason I've changed the conventional bearings on mine (and my 916) is that they got loose.

As long as they turn smoothly and not silly tight, I'd leave them.

yellowfever · 07-09-2024, 11:55 PM

Thanks all, useful info/sound advice.

I took pro advice on the three that have been changed previously. In the case of the horizontal cylinder they both stuck and nearly shredded the belt so they definitely needed changing. I had a narrow escape from disaster there!

So I’m going to leave the last remaining original tension roller in situ. And I’m going to return the v stiff new one I got as I don’t need it (yet) and I’m not so confident in it. All the ones on the bike will turn running a finger along them in direction belt would go (so like finger is a belt). Whereas with the new one finger just slides and roller doesn’t turn. It needs to be gripped between my fingers to turn it…

06-09-2024, 03:26 AM	#1
yellowfever Bronze Member Join Date: Mar 2006 Location: London Bike: S2r 1000 Posts: 251	Timing belt tension rollers - how should they feel if they’re OK? OK I appreciate checking belt rollers by hand is something of a dark art, acquired through experience. Or a waste of time unless really egregiously worn according to some. And trying to describe how something should ‘feel’ in a post is perhaps even more difficult. But anyway here goes nothing, any thoughts appreciated! How freely should they turn? Are new ones stiffer to start with? Background below… Whilst belts off to investigate oil leak on my 2006 S2R 1000 I’ve been checking the belts and rollers. Belts will be going back on as they look fine at 1.5 years old and I’ll be swapping them for new at big service next year anyway. On rollers the horizontal fixed and mobile rollers were both replaced in 2016 and the vertical mobile roller was replaced in 2014 and they all feel fine, rotating freely enough without any slop, noises or notchiness. The vertical fixed roller is still the original from 2006 complete with the weird special 10mm across flats bolt holding it in place. It also has no slop and turns OK but is noticeably stiffer than the others. I had thought I might replace it at some point as it’s the only original roller still left. I’ve been told it may only have been left in situ when the others were changed previously by pro mechanics as it still turns alright and because between the threadlock and weird bolt and difficult access they’re apparently not that easy to remove, so tend to get left in place unless they’ve obviously gone bad. I’d had the foresight to get a new OEM fixed roller from MSP as I expect I’ll need to replace it at some point. So I thought a useful cross check as I’m new to feeling belt rollers would be to see how freely the new one turned. Surprisingly it’s very stiff - more so than any of the rollers on the engine now including the fixed vertical one that I was thinking of replacing! it’s meant to be Ducati OEM and was €51, though it didn’t come with any Ducati packaging. Anyone got any idea if this is normal? Are new rollers stiffer at first? Or have I got a dodgy part I should return? Thanks in advance for any thoughts… Last edited by yellowfever; 06-09-2024 at 03:29 AM..

06-09-2024, 08:57 AM	#2
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,897	Not sure if S2R is the same but on my M900 there is the one 'special' long roller/bearing and the other is just 2 standard bearings fitted together. The special ones do seem tighter and they are expensive but I've never changed mine as they seem OK. The others are cheap enough to change every so often, in fact I changed mine a couple of years back as the front cylinder belt was 'tracking' against the edge of the pulley, leaving some rubber dust behind and the bearings did seem a little loose - all good now, at least last time I checked. __________________ M900, 916, LeMans II.

07-09-2024, 02:24 PM	#4
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,903	My 1991 750ss rollers at least 16 years and still fine my M750 rollers are 24 year old still feel fine, and the S4 is 23 years old and has had one roller changed . __________________ MONSTERMAN

07-09-2024, 02:33 PM	#5
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,897	All those that I have seen (mine plus a couple of spare I have) seem tight compared to conventional bearings, maybe due to the length of the rollers inside? It's likely they free up a little as they warm up, the only reason I've changed the conventional bearings on mine (and my 916) is that they got loose. As long as they turn smoothly and not silly tight, I'd leave them. __________________ M900, 916, LeMans II.

06-09-2024, 03:07 PM	#3
yellowfever Bronze Member Join Date: Mar 2006 Location: London Bike: S2r 1000 Posts: 251	Hi thanks for the reply. My mobile belt tensioner rollers have both been replaced in the past and are both the newer design in one complete piece with one long bearing on the shaft, not the two roller bearings next to each other held on one shaft by a circlip like the originals like you have. Mine have to be replaced as one item and not cheap, but happily they are both fine as is the other (also previously replaced) fixed roller (which always had the longer single bearing design). The remaining fixed roller is stiffer but still moves smoothly and is not loose so think I’ll be leaving it for now at least given it’s meant to be a pita to remove and the replacement I’ve got is stiffer still! Still not sure if I’ll return the new one as possibly defective… just don’t know if they all start off that stiff. I have only three data points that make no sense… Brand new = stiffest 2006 = next stiffest 2016 = least stiff

07-09-2024, 11:55 PM	#6
yellowfever Bronze Member Join Date: Mar 2006 Location: London Bike: S2r 1000 Posts: 251	Thanks all, useful info/sound advice. I took pro advice on the three that have been changed previously. In the case of the horizontal cylinder they both stuck and nearly shredded the belt so they definitely needed changing. I had a narrow escape from disaster there! So I’m going to leave the last remaining original tension roller in situ. And I’m going to return the v stiff new one I got as I don’t need it (yet) and I’m not so confident in it. All the ones on the bike will turn running a finger along them in direction belt would go (so like finger is a belt). Whereas with the new one finger just slides and roller doesn’t turn. It needs to be gripped between my fingers to turn it…