Why you change belts.

Mr Gazza · 02-05-2023, 06:46 PM

I popped the belts off my 750SS at the weekend to do a valve service and had a little surprise.

The belts are Exactfit installed two years ago. I did 16 miles to and from an MOT and the engine has not turned since while I've been playing silly beggars taking various bits apart.

I've tried to photograph some little indentations I found. The belts held their shape when removed and the dents were where the tensioner rollers sat.
They've since gone more round and the dents seem less deep.

Is this why it's really bad to leave belts sitting for ages? Not only were the belts rather stiff and set in shape, but those little dents will probably bump the rollers every time they go round and cause some local heating and stress.
Needless to say I won't be re-fitting them even though the Exactfit belts on the Monster are going into their third year, but you see I use that one.

Incidentally, I just ordered new Ducati belts from Moto Rapido via eBay. They were only £39.50 posted, I don't think I've ever bought belts that cheap. Exactfit are £71. So dive in there quick if you need belts for a 750/600/620/800

900Rebuilder · 02-05-2023, 06:58 PM

Do new belts have a lifespan do you know? I've got a set still in their cardboard sleeve from Ducati but they must be 10+ years old but have never been fitted

Mr Gazza · 02-05-2023, 07:05 PM

They should be fine if you have kept them coolish or at least at an even temperature and most importantly, out of light.
If I know I'm going to keep belts for while I just slip them out of the sleeve so they store in a more round shape.

I think I would probably buy new again after 10 years myself though. (How much did you spend on carbs?)

Luddite · 02-05-2023, 11:41 PM

Quote:

Originally Posted by 900Rebuilder

Do new belts have a lifespan do you know? I've got a set still in their cardboard sleeve from Ducati but they must be 10+ years old but have never been fitted

I was wondering about this recently as I've had some Exactfit belts in the spares box for a couple of years. As with Mr G, I always store them out of the light and removed from their cardboard sleeve, so they're perfectly round at the moment.

I did a bit of a search online and found a quote on another forum from Chris at Ca Cycleworks in response to just this question.

"If the belts are stored in plastic and away from sunlight, they have an infinite shelf life. Our manufacturer/importer stores samples from every batch of product he orders then checks the belts every year. Every year, they have consistently stayed "fresh".

We do have EU and UK distributor via Stu at ExactUK."

These Exactfit belts have always been touted as having a three-year operational life but, since Ducati have apparently extended the service life of OE belts on some of the earlier models to five years, http://www.ukmonster.co.uk/monster/s...ad.php?t=58960 I'm wondering if there's been any corresponding change to the recommended lifespan of the Exactfit belts. I must drop an email to Stu at Exact UK to see if he has any thoughts on the matter.

jamminbmx · 03-05-2023, 07:16 AM

I took my Exact fit off after 3 years and a few thousand miles. Looked basically mint. I could not see any damage. They did feel a bit stiffer than the new Exact belts but nothing serious...

900Rebuilder · 03-05-2023, 08:06 AM

Quote:

Originally Posted by Mr Gazza

They should be fine if you have kept them coolish or at least at an even temperature and most importantly, out of light.
If I know I'm going to keep belts for while I just slip them out of the sleeve so they store in a more round shape.

I think I would probably buy new again after 10 years myself though. (How much did you spend on carbs?)

Hahaha!

Whilst I'll buy some new ones the pile of bits I bought all those years ago included new belts and new tyres. Shame to chuck them away but better to be safe than sorry.

Dukedesmo · 03-05-2023, 09:15 AM

Personally, I think the hysteria over 2 year belt changes is just that, hysteria. I've left mine for 4 years before (though low mileage) and never seen any sign of impending doom and could probably have got another couple of years but 'bottled' it.

I think there were a few documented failures of 4V belts in the early days that prompted all this and that the belts in recent years are much improved.

However, to avoid any chance of catastrophic failure I wouldn't advise anyone to leave them too long, especially if you're not scrupulously checking them regularly.

As a bit of light entertainment, here's a picture of a cambelt that I recently had the pleasure of changing (along with all the valves) on my Son's car, it failed at around the recommended mileage for replacement though probably a couple of years past the time, note it didn't actually break and was still tight around the cams, it just lost it's teeth around the crank pulley.

350TSS · 03-05-2023, 09:56 AM

I have always thought that with desmo valve operation that the belts should have a relatively easy life compared to say a 16v car engine where 8 valve springs have to be compressed every revolution. The only possible downside in a Ducati application is the small radius of the camshaft jack shaft pulley and the comparatively tight radius of the tensioner pulleys, the tensioner pulleys on car engines tend to be about twice the diameter. The Ducati of course would probably also be revving slightly higher than a car engine as a general rule.

Dukedesmo · 05-05-2023, 10:02 AM

They're certainly easier to turn than fully sprung cams as evidenced when doing valve checks and turning the cams by hand.

The downside, compared to most car engines for the belts is the heat, speed (up to twice as fast) and, in the case of a 4V the quite severe reverse bend angles over the tensioners.

Leamreject · 05-05-2023, 03:55 PM

Quote:

Originally Posted by 900Rebuilder

Do new belts have a lifespan do you know? I've got a set still in their cardboard sleeve from Ducati but they must be 10+ years old but have never been fitted

Need to be stored out of sunlight, in a cool place & importantly away from items with electrical brushed motors such as fridge or freezers as the arcing from them causes ozone which accelerates rubber degradation.

900Rebuilder · 06-05-2023, 04:58 PM

Quote:

Originally Posted by Leamreject

Need to be stored out of sunlight, in a cool place & importantly away from items with electrical brushed motors such as fridge or freezers as the arcing from them causes ozone which accelerates rubber degradation.

For the price I'll get a new set and chuck both these and those on the motor now

adie851 · 14-05-2023, 04:46 PM

In the early days..90's... I used to change belts every two years.....now I do three to four years...so far so good.....like everyone says now.... Ducati have extended their service schedule for cambelts replacement to five years....better quality belts...? or just the same....be interesting to find out...thoughts people.... ?

02-05-2023, 06:46 PM	#1
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,963	Why you change belts. I popped the belts off my 750SS at the weekend to do a valve service and had a little surprise. The belts are Exactfit installed two years ago. I did 16 miles to and from an MOT and the engine has not turned since while I've been playing silly beggars taking various bits apart. I've tried to photograph some little indentations I found. The belts held their shape when removed and the dents were where the tensioner rollers sat. They've since gone more round and the dents seem less deep. Is this why it's really bad to leave belts sitting for ages? Not only were the belts rather stiff and set in shape, but those little dents will probably bump the rollers every time they go round and cause some local heating and stress. Needless to say I won't be re-fitting them even though the Exactfit belts on the Monster are going into their third year, but you see I use that one. Incidentally, I just ordered new Ducati belts from Moto Rapido via eBay. They were only £39.50 posted, I don't think I've ever bought belts that cheap. Exactfit are £71. So dive in there quick if you need belts for a 750/600/620/800 __________________

02-05-2023, 06:58 PM	#2
900Rebuilder Registered User Join Date: Sep 2022 Location: Beeston Bike: M900 Posts: 326	Do new belts have a lifespan do you know? I've got a set still in their cardboard sleeve from Ducati but they must be 10+ years old but have never been fitted __________________ Ducati Monster 900 - Yamaha tdr125 & dt200wr - Ford GPW

02-05-2023, 07:05 PM	#3
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,963	They should be fine if you have kept them coolish or at least at an even temperature and most importantly, out of light. If I know I'm going to keep belts for while I just slip them out of the sleeve so they store in a more round shape. I think I would probably buy new again after 10 years myself though. (How much did you spend on carbs?) __________________

03-05-2023, 09:15 AM	#7
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,894	Personally, I think the hysteria over 2 year belt changes is just that, hysteria. I've left mine for 4 years before (though low mileage) and never seen any sign of impending doom and could probably have got another couple of years but 'bottled' it. I think there were a few documented failures of 4V belts in the early days that prompted all this and that the belts in recent years are much improved. However, to avoid any chance of catastrophic failure I wouldn't advise anyone to leave them too long, especially if you're not scrupulously checking them regularly. As a bit of light entertainment, here's a picture of a cambelt that I recently had the pleasure of changing (along with all the valves) on my Son's car, it failed at around the recommended mileage for replacement though probably a couple of years past the time, note it didn't actually break and was still tight around the cams, it just lost it's teeth around the crank pulley. __________________ M900, 916, LeMans II.

05-05-2023, 10:02 AM	#9
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,894	They're certainly easier to turn than fully sprung cams as evidenced when doing valve checks and turning the cams by hand. The downside, compared to most car engines for the belts is the heat, speed (up to twice as fast) and, in the case of a 4V the quite severe reverse bend angles over the tensioners. __________________ M900, 916, LeMans II.

03-05-2023, 07:16 AM	#5
jamminbmx Registered User Join Date: Mar 2016 Location: oxford Bike: M600 Posts: 131	I took my Exact fit off after 3 years and a few thousand miles. Looked basically mint. I could not see any damage. They did feel a bit stiffer than the new Exact belts but nothing serious...

03-05-2023, 09:56 AM	#8
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,422	I have always thought that with desmo valve operation that the belts should have a relatively easy life compared to say a 16v car engine where 8 valve springs have to be compressed every revolution. The only possible downside in a Ducati application is the small radius of the camshaft jack shaft pulley and the comparatively tight radius of the tensioner pulleys, the tensioner pulleys on car engines tend to be about twice the diameter. The Ducati of course would probably also be revving slightly higher than a car engine as a general rule.

14-05-2023, 04:46 PM	#12
adie851 Member Join Date: Jan 2015 Bike: S4r Posts: 104	In the early days..90's... I used to change belts every two years.....now I do three to four years...so far so good.....like everyone says now.... Ducati have extended their service schedule for cambelts replacement to five years....better quality belts...? or just the same....be interesting to find out...thoughts people.... ?