Hi all, I'm recommissioning my '95 M900 Monster (carb model) although I replaced the cam belts only 1000 miles ago, it's done 11,000 now so well within the cam service time. The '95 service interval is 18500 miles. It's been off the road for a number of years. And not started for about a year when I rebuilt the fuel pump and started it on a remote tank. The question is; do I replace the belts now? If I do, I'd like to replace the tensioner and idler bearings. Is there a 1995 parts book available? The only one I can find is for the 400. I have suppliers for top quality bearings, so if I can identify them I can probably source them. Thanks, sorry about the long post but more info is better. Lol.
The tensioner and idler bearings are different to each other; one of them uses 2 x 6201-2RS/C3 bearings side-by-side whilst the other is (I believe) a Ducati specific 'long' bearing. The long bearings last well and so are probably OK but you would likely need to get them from Ducati whilst the others are a standard bearing, available at any bearing supplier - I had a situation where one of these was a little 'wobbly' and it caused the belt to lightly rub, witnessed by a build-up of rubber dust inside the cover. I use exact-fit belts; https://www.ducati.tech/ and they can supply the bearings along with the belts if required (tip - sign up as a member/paid subscription on 'another' Ducati forum for a discount which will save you more than the subscription fee). Parts manual should be around somewhere online, I've got one from a 2001 M900 which, although fuel injected the belts etc. are the same. I'm also fairly certain that the smaller engined Monsters 400/600/750 use the same bearings although the belts are different.
The service interval for the belts on your bike is 12,000 miles or 2 years, whatever comes first. You don't say how long the since the belts were changed but if more than a couple of years ago I'd change the belts, if less than 2 years it should be OK for another year. I previously owned a 907ie, the handbook only specified 12,000 miles with no mention of time: I bought the bike at 20 years old with 27,000 miles on it, the previous owners had only had the belts changed twice! It had survived belt changes at 12,000 miles but about 8 or 9 years apart. The engine for your bike is the same as the 91-97 900SS, parts list for which are readily available online. If you can't find a copy message me and I'll send you one. at only 11,000 miles the cam belt tensioner rollers should still be good unless the bike has been stored in a damp environment. With the belts off check to see that the roll freely. If they do leave well alone. In theory the bearings on the movable tensioner can be replaced although I've never managed get them off the tensioner arm. Those on the fixed roller are integral with the roller assembly. So replacing the bearings gets quite expensive at £50 a pop for the fixed rollers. I've attached copy of the service schedule for your bike.
Get them off by force if required, a pulley extractor should do the job and it doesn't matter if you damage them as long as the arm/shaft is kept nice. As for fitting the new ones; freeze the shaft in your freezer and heat up the bearings and they'll drop on nicely without any force required.
Thanks, I've checked out Exact Fit and the kit comes with SKF bearings for about 1/2 the price I've seen elsewhere. So I'll go with those.
Finally got around to ordering the Exact Fit belt kit. I'll fit it in the next couple of days. Fitted a new AGM battery while I'm at it. About half the price of the original style battery and they won't ship with acid anyway.
I removed tensioner bearings using a vice and some sockets before I bought a press. The fixed bearings are a different story, they can be hard to get out. The original version of these did not have a full hex head so you could only get a 10mm open end spanner on there and with the thread locker used they don't want to come out. Mole grips might get it out otherwise welding a nut on the end will do the job.
Got the belts off and started on the idler bearings The rear one slackened relatively easily but the front one won't budge. I didn't get them with the kit just the tensioner bearings. Anyway having checked them for rotation and wobble they are like new so I'll leave them until next time. It's done under 12,000 miles.
The tensioner bearings wouldn't submit to the puller so the angle grinder with a thin wheel er..extracted them. So the new bearings were fitted with the help of a 12mm deep socket. And started on the belts. The rear one is a PITA as the cam is on the spring and it doesn't stay on the mark. The first attempt ended up one tooth out so I'll get back on it tomorrow. I can't remember how I did it last time. Oh I removed the rear idler bearing cleaned it up and refitted with new thread lock.
If the rear/vertical cam is 'on the spring' it sounds like you're fitting the rear/vertical belt at the TDC of the front/horizontal cylinder. It's a while since I've done this but shouldn't each belt be fitted at its own TDC?
The V cyl will have its intake cam open when H is at TDCC hence the spring pressure. There’s no option but to lock the cams on a desmoquatro or just move it back on a desmodue and hold it in position as the belt is put on. However, you should turn the V cyl to TDC before setting the tension of the belt or else the cam pulley is exerting tension on the belt.
Yes, interesting about the pulley putting tension on the belt. I' ll set it roughly (about 10lb tension) before setting the V cylinder at TDC and final tension. A good guide if you don't have the Ducati tool is you should just about be able the turn the belt through 90° on the longest run using finger pressure. This is true of any toothed belt.
Or you can use the Allen key method, iirc 5mm yes 6mm no, as to whether or not you can move the Allen key between the belt and the fixed bearing. TBH it’s not a do or die situation, get anywhere near the correct tension and it’s fine. Measure it again after a few revolutuons of the engine after setting it and it will have changed.
Anyway got the belts on. I used a pair of large fine nose pliers to hold the vertical cam wheel on the mark. A bit fiddly, why Ducati have such an aversion to using proper hex nuts I don't know but it doesn't make things easy. Would have been a doddle to hold it with a spanner. I suppose if you want to wreck a perfectly good socket, you could carefully measure and cut the four teeth to engage with the slots on the "nut". That's what I'll do if I ever need to remove the cam wheels.
Thought it was 45 Deg, that's what the performance bike article said, and the ' rule ' I've been using
rather than award you an unfriendly "disagree" "smilie", i will reply and say, in my opinion only obviously, but i'm certain it's the same opinion in general, that you cannot say the "90 degree (or any other fixed degree) twist" rule is true for any toothed belt. The amount you can twist a belt depends on several things, but the obvious one is the varying distance between pulleys/tensioners which will show a corresponding varying "twistable free play" for the belt, generalising.
