Belt replacement 749R - what do the cam pully dots align with ? - Ducati.ms

KiwiEd · Jan 9th, 2012, 1:42 pm

OK ... I'm feeling a tad stupid here.
I've been servicing and rebuilding my 996/748 race engines for 15yrs but I'm now in the throes of reassembling my 749R engine/bike for the first time (a restoration project that has dragged on for a very long time).

I'm at the point of fitting pistons, cylinders, setting squish and then cam timing.

As I'm planning the procedure I can't seem to figure out what the cam pully timing dots align with on the heads when refitting the belts. On the 996 the rear cam dots align with marks on the top of the inner belt covers and the front cam on the sides.

There do not appear to be any such referance points on my 749R ??

Am I missing something or do I have to use tool # 88713.1791 to lock the pulleys ....... surely not !!

I realise they are only the starting points and then future referance point for the cam timing, but where are they ???

Thanks in advance.

Andrew · Jan 9th, 2012, 1:57 pm

I can't comment on the 749R, however when I changed the belts on my 1098R I noted for the first time on one of my Ducati's that the cam pulleys had timing marks.

On the 1098R there are no apparent alignment points however I did observe that when the vertical cylinder was a top dead centre and the valves closed, the two alignment marks on the horizontal pulley pointed to one another and formed a straight line through the axis of the centre of the cams.

This was especially useful as the 1098R has also eliminated the timing window in the crank case, so I aligned the horizontal cams as indicated above (to give me a reference mark) and then I could remove the belts without fear of the vertical cams moving.

Andrew...

ZDM · Jan 9th, 2012, 2:40 pm

Give this a shot, it's a very good tutorial of the procedure. This is part 1 of 3.....if I recall correctly the dots don't make a whole lot of sense as they do on the previous Desmo models...

Ducatitech.com: Ducati 749/999 Timing Belt Change Part 1 - YouTube

TomTom · Jan 9th, 2012, 3:46 pm

Good advice in the vid.
Although if you have already taken the belts off and didnt make markings; Check the vid and notice the cam shaft axle is T-shaped, on horisontal the legs of the T will point forward aligned with the cylinder and on the vertical they will be retarded 135 degrees (equals 270 crank degrees) from that, see vid again and you get it.

If anyone has an 1198 and read this, it does NOT apply (well of course...its made by ducati, why be consistent lol).

KiwiEd · Jan 9th, 2012, 4:06 pm

Thanks ZDM and TomTom.

It is good advice in the video but I stripped the engine almost 2 years ago and didn't take note of the cam marks ..... just assumed that the reassemble would be similier to the desmo.

I now see why the tools (88713.1791) are used for refitting the belts.
Still, as long as I can get them close it'll be ok since I'll be dialling them in anyway and then I'll make some referance marks.

As an aside .... is 106/110 the best timing for the 749R race engine with an 848 kit ?

timmyho414 · Jan 9th, 2012, 4:06 pm

and once you've done all that and the timing is correct; make your own makes with a punch. Set the crank as you would on your desmoquattro's and punch the head next to the dots on the cam gears. It make next time so much easier.

MotoRev make a sweet tension measuring tools if you don't already have your own method. I know some guys use guitar tuners or Allen wrenches, there's probably an 'app' for all I know but this thing is super easy to use. That, and I'm a sucker for nice tools.

KiwiEd · Jan 9th, 2012, 4:21 pm

Quote:

Originally Posted by timmyho414

and once you've done all that and the timing is correct; make your own makes with a punch. Set the crank as you would on your desmoquattro's and punch the head next to the dots on the cam gears. It make next time so much easier.

MotoRev make a sweet tension measuring tools if you don't already have your own method. I know some guys use guitar tuners or Allen wrenches, there's probably an 'app' for all I know but this thing is super easy to use. That, and I'm a sucker for nice tools.

Yep, I'll be doing that !!
I have one of the old tools for tensioning the desmo belts.
Chris from CJS in the UK (Duc guru) advised me last year to set the belts at 10 on the old gauge for timing and then back to 2 after the cams are set.

TomTom · Jan 9th, 2012, 4:54 pm

Regarding cam timing, what static compression will your build render? And also what max rev are you going for? ie, what part of the rev range is more important pre 8,5k or past?

pone 13:1, its not an awful lot of difference, but staying at 106 will give a few vital horses up to 9k, retarding it will lift it a tad at 10.5-11k up.
The gain up top is short compared to the advanced timing style which is there from bottom up to the point of shift over at approx at 8,5-9k.

**ST3S** · Jan 9th, 2012, 5:19 pm

KiwiEd · Jan 9th, 2012, 5:28 pm

Quote:

Originally Posted by TomTom

Regarding cam timing, what static compression will your build render?
Around 13:1 106/110 is fine, higher and you can retard inlet a bit.

I don't know what the comp will be. I think Mark from Ducshop has done a few of these (kit was purchased from him) so I can ask him, otherwise I'll work it out.