Tech Library - 748 Cambelts

There’s a lot of anecdotal information about cam belts, which ones fit models and interchangeability, this article might help (or confuse things). it is based on info available from Gates, the cambelt makers and was compiled July 2007, it might not be 100% accurate and you should check with your Ducati dealer for correct part numbers and tensions before ordering or fitting a cambelt.

Why are belts important?

These photographs show what happens when a belt fails, in this case the failure was caused by incorrect tension adjustment.

Belt Specification

Belts can be identified by a code printed on it.
The 58095 means profile type 58, and teeth on belt 095,17 is the width in mm

Two lengths of belt are in use 93 and 95 tooth. R spec models may have 21mm wide belts and a 19mm also exists.

All the Ducati OE belts have the OE part number printed on them. It differs in some cases from the OES number because of the sleeve. Make sure that the correct OE number is printed on the belt (it is usually very very faint but legible).The colour of the writing has no real importance. What counts is the OE part number. For imaging at some stage Gates were asked to print in red. It may be that there are also belts with green printing used on race prepared SuperBikes

 

Dimensions OE PN Material Model OES PN
58093x17 737.4010.1B 1st Gen   737.1004.1A
58093x17 737.4010.2B 2nd Gen   737.1007.1A
58093x17 737.4010.3B 3rd Gen ST4S/01-748 B/02 - S4R 737.1010.1A
58095x17 737.4011.1B 1st Gen 996-748 B-SPS/99 737.1003.1A
58095x17 737.4011.2B 2nd Gen 748-996 B/01 737.1006.1A
58095x17 737.4011.2C 3rd Gen   737.1009.1A
58095x19 737.4011.2D 2nd Gen   737.4011.2D
58095x21 737.4017.1A 3rd Gen 748R/02 737.4017.1A

This next piece of advice relates to a specific year/model of 748 but also explains the 1st, 2nd and 3rd Gen term used in the table above.

The main difference in the belt construction:
 
737.1003.1A (1st Gen) is a basic HNBR compound construction with better high temperature performance than previous CR constructions.
737.1006.1A (2nd Gen) is a development of this belt with HNBR rubber compound which has an aramid fibre load to improve mechanical properties especially at high temperature, and an improved glass fibre cord with better flex resistance.
 
The later bikes were fitted with 737.1009.1A. (3rd Gen) This has the same compound and cord as 737.1006.1A but the fabric on the teeth is lubricated to improve wear resistance and running temperature. This is the best belt available for the application without having to change pulleys to accommodate a wider belt.
 
On the 748 model this info applied to it is highly recommended to use the 737.1009.1A which is dimensionally interchangeable but which has a much better load carrying capacity.

Please note that this info might not be 100% accurate, the belts are supplied for a specific engine but the belt maker does not know which models that engine goes into.

 

So, where does this lead?, first check with Ducati for the correct belt for your model/year, then check that the length and width is correct and finally that the belt is of the latest construction. After that it needs to be installed to the correct tension as recommended by Ducati.

Belt Life/Replacement Intervals

Ducati have recommended a repalcement interval of every 2 years for belts ( possibly being altered to mileage on bikes after Aug 2007). The often asked question are "why is it shorter than a car?"

In terms of belt change intervals, they are usually based on the ageing of the rubber compound, the wear of the jacket material and the fatigue of the cord. These factors are determined by heat, time and work done (mileage/revs).

Generally the Ducati applications run at high temp, high revs and with high loads on small pulleys, and therefore age quite quickly (hence the 2 years). The later generation compounds which, in general, are more heat resistant with better load carrying capabilities age more slowly. The development of the cord and jacket materials also helps to increase the durability. In the meantime Ducati have also increased the load and
running temperatures just to knock back the life again!!

It is adviseable to follow the Ducati recommendations but if the belts look good (no signs of tooth root cracks or cracks on the back of the belts) and if the cold tension levels have not changed from previous measurements, then the belts should be OK but it is difficult to say for how long. Hence if somebody decides not to change them it is important
to visually monitor the state of the belts (at their own risk and we cannot recommend this obviously!).

The "set" theory that a belt develops a bend when the engine is not run for long periods of time is true. If you take a belt off the drive when it is cold, it maintains the shape of the drive. Once running and hot this disappears.

The load at start up is higher because the drive accelerates from stand-still to running speed (this is true whether the engine is hot or cold).
The rubber is also harder when cold and the force needed to bend it round the pulleys is higher. The engine has also less oil in circulation and so more friction.
I'm not 100% sure but the change in viscosity of cold oil and hot oil may vary the load on the desmotronic cam actuators slightly . This again would favour hot conditions not cold.


Please note however that the belt tension increases enormously when hot and this can react negatively on belt life.

 

More info or updates might be found in this discussion thread on the forums.

Thanks to Keith at Gates for his help compiling this article.

Please note that Ducati-UpNorth.com cannot accept any liability for the accuracy or content of this section. Visitors who rely on this information do so at their own risk. If you are unsure it's worth contacting your local Ducati dealer who will be able to help. Do not attempt a repair or modification if you do not have the correct tools or knowledge to do so.