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31-07-2020, 07:45 PM | #1 |
Registered User
Join Date: Jul 2018
Location: Caernarfon
Bike: M750
Posts: 40
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Ducati Monster 750 belts
Please can someone explain/justify the need to change belts every two years on these machines? I ask because with this virus event my normally low annual mileage, around a thousand miles a year, is now practically nil. When I changed the belts on purchase the originals looked fine. Why are they so fragile, it's not like they are dealing with a highly tuned engine? Thanks.
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'40 Indian Chief, '80 Moto Guzzi Le Mans MK 2, '97 Buell S1 Lightning, '98 Ducati M750 Monster |
01-08-2020, 07:16 AM | #2 |
Too much time on my hands member
Join Date: Jan 2013
Location: Shipbourne
Bike: M900
Posts: 1,422
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I have always wondered about this, with desmodromic valves they do not even have to cope with compressing valve springs so they do not have a big longitudinal load on the belts.
I think it may be because the pulleys are so small when compared to a car engine (although most car engines use the difference in size of the pulleys to get the half enine speed needed for the camshafts so the crankshaft pulley is often not that much biggger than a Ducati one) so the belt has quite a small radius to get around which maybe causes the belts to delaminate internally and therefore have a shorter recommended life. |
01-08-2020, 08:07 AM | #3 |
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Join Date: Sep 2010
Location: Leics
Bike: M900
Posts: 2,888
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I don't think they need to be changed every 2 years. Sure that's the recommendation but I'm sure they'd last much longer.
On the 4 valve engines there is much more of a reverse bend around the tensioner pulley and so presumably more stressed. Also compared to a car, they run faster and (likely) hotter, combine that with the small cam pulleys (as above) and some allowances should be made. I think a lot of the hysteria comes from 4-valve engines in the early days suffering broken belts but I think that is no where near as prevalent now due to better belts etc. I do mine at 3 year intervals and even that is probably overkill on the Monster? but, having last year dealt with the consequences of a broken cambelt on my Son's car I'd prefer not to take too many chances because if one does break it will not be good. To quote Mr. Eastwood - you have to ask yourself, do you feel lucky? well do you?...
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M900, 916, LeMans II. |
01-08-2020, 09:21 AM | #4 |
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Join Date: May 2013
Location: Norwich
Bike: M900sie
Posts: 5,935
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Good answer..
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01-08-2020, 09:25 AM | #5 |
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Join Date: Jul 2018
Location: Caernarfon
Bike: M750
Posts: 40
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Thanks, I've been running my Buell with all the "must change" parts on for many years now, even though I've acquired all the "correct" pieces, so I'll have to fit them for a sale and the same for my Monster, I'll run the belts till I want to sell, at which point I'll have to change them. I'll let you know if they snap in the meantime.
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'40 Indian Chief, '80 Moto Guzzi Le Mans MK 2, '97 Buell S1 Lightning, '98 Ducati M750 Monster |
01-08-2020, 09:43 AM | #6 |
Lord of the Rings
Join Date: May 2013
Location: Norwich
Bike: M900sie
Posts: 5,935
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Spoiler alert!
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Last edited by Mr Gazza; 01-08-2020 at 09:48 AM.. |
01-08-2020, 11:19 AM | #7 |
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Join Date: May 2007
Location: Stockbridge
Bike: M900
Posts: 1,984
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Ouchy Ouch!
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Original and Best since 1993 |
01-08-2020, 07:27 PM | #8 |
Too much time on my hands member
Join Date: Jun 2007
Location: Forest Of Dean
Bike: S2r
Posts: 3,205
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A pot of Ali Devcon will take out those little imperfections and all will be well again
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"The final measure of any rider's skill is the inverse ratio of his preferred Traveling Speed to the number of bad scars on his body." Song of the sausage creature |
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