Setting Belt Tension
- Thread starter Bitza
- Start date
walkingpictures
preneolithic frebie
Don't know about the 2v but as I understand it the frequency app works on the 4v or old school is a 5mm allen key.
Someone will be along shortly for better advice
Someone will be along shortly for better advice
I use the allen key + twist methods, works fine.
I have tried frequency using my phone but found the results too variable for my liking though, having set them by the old school methods the frequency is about right on the occasions where I get a steady reading. Maybe a dedicated tool is better?
For the 4v I have a Facom belt tension tool (spring-loaded, deflection) that is reliable and repeatable (and also corresponds to the twist method) but, unfortunately it doesn't fit on a 2v belt run.
IMHO, I reckon it's not as critical as many would have you believe (especially on 2v motors) but obviously needs some mechanical sympathy/knowledge to get it right plus, if you've ever checked your belts a year after fitting you will find they are significantly looser but still working fine.
I recently changed the cambelt on my Son's car and the tension on that is set by a spring-loaded pulley so no messing about with gauges/allen keys/frequency/voodoo etc. and, I was somewhat surprised that the crank pulley was free on the end of the crankshaft with no locating keyway/spline etc. to stop it moving, held in place purely by tightening the nut - the nut did require a huge torque setting though.
I have tried frequency using my phone but found the results too variable for my liking though, having set them by the old school methods the frequency is about right on the occasions where I get a steady reading. Maybe a dedicated tool is better?
For the 4v I have a Facom belt tension tool (spring-loaded, deflection) that is reliable and repeatable (and also corresponds to the twist method) but, unfortunately it doesn't fit on a 2v belt run.
IMHO, I reckon it's not as critical as many would have you believe (especially on 2v motors) but obviously needs some mechanical sympathy/knowledge to get it right plus, if you've ever checked your belts a year after fitting you will find they are significantly looser but still working fine.
I recently changed the cambelt on my Son's car and the tension on that is set by a spring-loaded pulley so no messing about with gauges/allen keys/frequency/voodoo etc. and, I was somewhat surprised that the crank pulley was free on the end of the crankshaft with no locating keyway/spline etc. to stop it moving, held in place purely by tightening the nut - the nut did require a huge torque setting though.
To add, you can't use the allen key method on 4v as the tensioner pulleys have a lip on them preventing the key from fitting between belt and roller rather than just bearings like the older 2v.
Don't know if that might also be the case on newer 2v?
Don't know if that might also be the case on newer 2v?
I've always done mine (M750) with a 5mm allen key.
I'm probably on my eighth set of belts by now and never had a problem.
But like DD says, it does all depend on having a half decent mechanical feel.
I usually practice on the old belts quite a lot before removing them, just to "get my eye in".
My personal opinion is also that the tension isn't massively critical as long as they're not too tight.
My preferred method is to use one finger on either side of the pulley to pull the belt away and then use the allen key to gauge the gap rather than attempting to judge the force needed to push the key between belt and pulley. And I use 5mm and 6mm keys as "go" and "no go" gauges.
I've never used a frequency method but if I did, I would still check it with the allen keys and if there was a discrepancy I would probably be more trusting of the allen keys.
One thing that is very handy is that I've changed the oil cooler lines such that they now both run on the left side of the motor, per Gazza's recommendation (memory says you use hypermotard lines).
This makes removing the belt covers a much easier and quicker job.
Also, I have put a secondary paint dot on the cam pulley on the vertical cylinder (90 deg from the factory mark) to aid resetting that cyl to TDC when checking its tension.
I've always used std Ducati belts in the past and usually run them for 3yrs rather than the recommended 2yrs.
This time I used Exactfit belts and plan to run them for 4yrs.
I don't exceed the recommended mileage limits though.
I'm probably on my eighth set of belts by now and never had a problem.
But like DD says, it does all depend on having a half decent mechanical feel.
I usually practice on the old belts quite a lot before removing them, just to "get my eye in".
My personal opinion is also that the tension isn't massively critical as long as they're not too tight.
My preferred method is to use one finger on either side of the pulley to pull the belt away and then use the allen key to gauge the gap rather than attempting to judge the force needed to push the key between belt and pulley. And I use 5mm and 6mm keys as "go" and "no go" gauges.
I've never used a frequency method but if I did, I would still check it with the allen keys and if there was a discrepancy I would probably be more trusting of the allen keys.
One thing that is very handy is that I've changed the oil cooler lines such that they now both run on the left side of the motor, per Gazza's recommendation (memory says you use hypermotard lines).
This makes removing the belt covers a much easier and quicker job.
Also, I have put a secondary paint dot on the cam pulley on the vertical cylinder (90 deg from the factory mark) to aid resetting that cyl to TDC when checking its tension.
I've always used std Ducati belts in the past and usually run them for 3yrs rather than the recommended 2yrs.
This time I used Exactfit belts and plan to run them for 4yrs.
I don't exceed the recommended mileage limits though.
I always watch these two youtube demos before doing anything at all.
Just to get my head in the right place, cos after all it'll be 3 years since I last did it and the detail fades from memory.
In both of these, they reference that, with the horizontal cylinder at TDC-firing, the horizontal cam is free to turn but the vertical cam is under the influence of the helper spring.
This will then affect belt tension on the vertical belt ... hence the resetting to TDC-firing on that cylinder before setting tension on that belt.
I have always wondered about the view that 6mm should be used instead of 5mm on the vertical cylinder.
I think I've heard it said that it is to account for increased expansion of the hotter vertical cylinder, but I've never been convinced by that.
I'm more inclined to think that it is instead to make some allowance for the aforementioned helper spring effect if setting the vertical belt tension without resetting to TDC-firing.
I use 5mm (go) and 6mm (no go) on both cylinders but always reset as appropriate.
For the record, I always fit the belts and set tension approximately before rotating the engine as many times as I can be bothered, to settle the belts before final tensioning. Brad's video describes this kind of stuff particularly well.
Just to get my head in the right place, cos after all it'll be 3 years since I last did it and the detail fades from memory.
In both of these, they reference that, with the horizontal cylinder at TDC-firing, the horizontal cam is free to turn but the vertical cam is under the influence of the helper spring.
This will then affect belt tension on the vertical belt ... hence the resetting to TDC-firing on that cylinder before setting tension on that belt.
I have always wondered about the view that 6mm should be used instead of 5mm on the vertical cylinder.
I think I've heard it said that it is to account for increased expansion of the hotter vertical cylinder, but I've never been convinced by that.
I'm more inclined to think that it is instead to make some allowance for the aforementioned helper spring effect if setting the vertical belt tension without resetting to TDC-firing.
I use 5mm (go) and 6mm (no go) on both cylinders but always reset as appropriate.
For the record, I always fit the belts and set tension approximately before rotating the engine as many times as I can be bothered, to settle the belts before final tensioning. Brad's video describes this kind of stuff particularly well.
Mark64
UKMOC Member
On the testastretta engine you have to use a tool to check the belt tension (110hz I think) I always used the gates carbon drive app just using my phone, I double checked it using a genuine Ducati tool and it was identical, not bad for a free app.
Reading through the procedure in the official workshop manual for my M750, I notice/recall that although it recommends using a special tensioning tool to set the tension on the horizontal belt, it then goes on to state that if the procedure is carried out with the engine in the frame (ie nearly always) then the tensioning tool cannot be fitted to the vertical cylinder and the vertical belt tension should be set by comparison to the horizontal belt.
This was printed before the days of frequency methods so one presumes they mean just a manual comparison ... no details are given.
My take from this is that the tension is not particularly critical and there is a wide range of acceptability (as long as they're not too tight).
This was printed before the days of frequency methods so one presumes they mean just a manual comparison ... no details are given.
My take from this is that the tension is not particularly critical and there is a wide range of acceptability (as long as they're not too tight).
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Martin C
UKMOC Member
For many years I have used an old-fashioned and simple “spring balance” from a hardware shop. The hook fits around the tensioner pulley, and my Haynes manual quotes a tensioner pulley pull of 10lbs, then tighten the bolt. I originally checked the balance’s accuracy using bags of flour.
Mark64
UKMOC Member
Graded grains?
;-)
;-)