Looks like the crankbearings have gone on my 996s has anyone done these and what like a job is it to do?
Currently in the middle of a full rebuild of the Monster engine, not actually removed the bearings yet but am at the point of being able to. Bit of a job splitting the engine, you'll need some special tools and inevitably some other parts whilst you're in there but as long as you've got time, patience and a clean (preferably warm) place to work then it's not too bad (so far). Here's where I am at the moment;
I am very tempted to give it a go, its either that or go to my nearest duke dealer which i think would cost in the range of £2000 as i need a new stator cover which is £502 and with the other parts and labour probably wont be far off the 2k
Get a cover from ebay or a breaker for much less than £500 (I have a used ST2 LH cover I'd sell cheap but I don't think it'll fit a 996?) then even with tools/parts etc the bill would be considerably less than £2k - it's the labour that's the killer, you're paying for a full engine rebuild time-wise which is probably based on a couple of days (16hrs +) labour, especially if you deliver the bike rather than the engine to them. I've yet to find out what the cost of bearings/seals etc is but I'm guessing around £500ish.
I think its the st4 that shares the same casing cover,i will keep looking on ebay hopefully 1 will come up i am very tempted to do the work myself as this would be considerably cheaper, I have been looking into it,how do i set the preload on the crank bearings i take it its not as simple as taking the old bearings out and fitting new ones and rebuilding the engine?
ST4 was 916cc so may still have the 916 single-phase alternator? ST4S was 996cc so should be good? As for bearing preload, I'm hoping it will be a straight swap but as I've not done it before I'm still finding out, I had considered taking it to a specialist but want to build it myself. But I'm not in a rush so don't need it fixing quickly which is a good thing because I've messing with this bike for 2 years now! (although only split the engine today) but I would like it on the road for next summer so am now planning to pull my finger out.
I know the feeling i want to do it all myself too but if it comes to it i might have to get this part done at my local dealer i also have a presision engineering company nearby they would probably be able to help with this
The bearing preload is critical to it all being worth while. It's impossible to assume that simply replacing the bearings will be correct. Measure everything and be 100% you have the right figures. If in doubt, measure again. Ultimately, it's how the crank feels when the cases are closed up. Get this right and it'll be better than new. Get it wrong and if loaded too much, it'll fail again and quite quickly. I built a motor this year that had been done 800 miles prior.......and that was in the trade. the rest of the engine is pretty straight forward. If you have any doubts, get it to a decent workshop. Not sure where you are, but I'm happy to help out. Done several now for ppl doing their own rebuilds and for the sake of a couple of hours labour, you could save having to do it again...
Good info from Nelly, further to which (and my visit today) I'll be getting him to do this job. Best leave some jobs to the experts and this is too important to risk me cocking it up I think. I really only want to do it the once.
Nelly what all do you require to set the preload, the cases, bearings and crank or do you need the whole engine?
Any chance of answering this Nelly, so we can see and learn. Hope that I never have todo this job, but am interested to learn what and why preloading the bearings/cases is all about. Thanks.
I have a mate who is a precision engineer explain it to me, I fully understand what it means but dont quite know and dont have the tools to put it into practice ,and although i am confident in trying to do it on my own i am getting a little fed up of my 996 letting me down and costing me a fortune that maybe its time to give it to someone for a major overhaul
Eyore- its quite difficult and long winded to explain, Basically all angular contact bearings, better known as ball bearings are manufactured with clearance between the balls and races. In a high revving engine or even a piece of machinery these clearances might be too big depending on what you are using them for, revs temperature etc will all make a difference to the clearance you need in your bearings. In the case of your crankshaft if you have too much clearance you will get too much vibration and noise from the bearings and also your crank can bend and flex too much. This could result in the bearings spinning in the crankcase or failing early. If you think of your bearing in basically 3 parts outer race, inner race and balls. The outer race would have to fitted inside the crankcase then sims fitted to push against the inner race to give you the correct end float on yer crank (sideways movement) and correct lift (up and doon) Obviously if they are shimmed too tight when cold then when you are thrashing the hoore and she gets hot the bearings will become too tight, possibly damaging the bearing races, causing the bearings to spin in the crankcases and destroying them. That is worst case scenarios but if they were slightly tight you would lose all important power and they would wear prematurely resulting in you having to do another rebuild earlier than you want to.
