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Primary noise

Ok here comes a Technical question or two and not the usual where's my 961 so hopefully I will be safe from the thread snipper. Anyone any idea why some 961's are more noisy than others in the primary drive, my 961 with the clutch leverreleased sounds like a bag of bolts in a blender with shot bigends, pull the clutch in and although still slighty noisy is more than acceptable. Before someone replies they all sound like that they dont as I have heard some MCT built 961's and I would be more than happy if mine sounded like them and I have alsoheard another Donnington built engine like minewhich sounded aboutthe sameas my one. Is it the components used had better tolerences then or were they assembled better? do they get shimmed for better fit or do they just get put on and fit were they touch. Factory don't really want to know as I made a big point of it when it went in for it's first service and it came back sounding just the same with the usual line they get quieter when they run in, mines done over a thousand miles and is definately no quieter and I can't see how straight cut gears will get quieter with use, if anything I would have thought they get noisier as they wear. Anyone out there fancy developing a belt drive ?

AlsoI read somewhere that the engine has 3 litres of 10/40 oil and the gearbox 1.2 litres of thesame 10/40 oil. Is the gearbx oil then separate from the engine tank/sump oil and if so how is the level checked and filled or does the same oil circulate the whole lot and what of the primary drive is that separate again or same as the engine. Before anyone says look in the manual I think Coco the clown and his mate wrote that when they felt like havinga laugh and is not much use except propping up a wonky table, did come in a nice leather wallet though.

Thanks

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Hi Colin,

I know nothing about the 961 and this may be a bit picky but if the noise tends to go away with the clutch pulled in then it is probably the gearbox and not the primary drive.

Does the noise change if you go into gear ? If so then it suggest something related to the mainshaft (which is now not rotating as you are in gear and going nowhere).

This may be anopportunityfor someone who knows a lot more about gearboxes than me to come up with somesuggestions.

Tony

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Colin, as you know this noise is caused by gear teeth rattling together. All power transmission gears must have some backlash, for production and operational reasons. [gear trains in machine tools are sometimes made to have no backlash]. Any backlash tends to increase as alloy housings expand. The noise results from cyclic variations in the rotation of the motor, which are greatest at idle speed.

These variations can be reduced by speeding up the idle to the point where there acceptable, and sometimes by reducing the ignition advance at idle to make for smoother running. Gear rattle often occurs in car gearboxes ,and is objectionable to the occupants of an otherwise silent running car.Typically, car makers fit Backlash Eliminators to noisy transmissions. These cheap and simple devices completely eliminate gear rattle at idle,and have been fitted to millions of cars. My car has one.

Regards John.

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I agree with John; it does sound more gearbox than primary drive related, according to Colin's description of the symptoms. I have a BMW 1100 GS, which has a gearbox with 'o' rings fitted to the gears to damp backlash and minimise 'chatter'. This is a later version; the earlier ones with no 'o' rings being particularly rattly when hot. This sounds similar to what John describes relating to car gearboxes.

Unfortunately we still have no explanation why Colin's bike is noisier than other 961's, except perhaps variation in the amount of backlash from gearbox to gearbox. If it were down to idle speed adjustment, ignition timing etc, then the factory would have sorted it out at the service, wouldn't they?

Given that these bikes haven't been around long enough to have worn out, it would seem that this difference in backlash is down to varying production tolerances in manufacture. If it were true that 'they all do that, sir,' then his bike would be no noisier than other examples.

If it were mine, I would insist that the factory sorted it out.

How long is the warranty on a 961 (miles/time from registration?) I would be really disheartened to find my bike ran out of warranty whilst I was waiting for it to get quieter!

As to the owners manual not giving adequate information, is this because the factory don't want anyone working on the bikes? I would still have thought that something like oil levels would be an important thing for owners to know about. Perhaps a Haynes manual is needed!

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I don't claim it's one thing or the other, although I would expect primary? It's easy mit Beemers, keine primary so the noise has to be the coggenbox.{Proper BM's we're talking about, not those other horrible things.} The car rattle eliminator is a narrow gear mounted on the end of a gear and spring loaded to take up backlash. What can the service dept do , well years ago I worked in a GM service dept and there were a lot of Opels with noisy diffs, the service manager put heaps of pressure on me for a cure,so I fixed em, no more noise. The national service guy came to the dealership to find out the cure. Simple I said, I mix up a special oil for the diff. Show me ,he said, so I pumped out a pint of diff oil and then grabbed a handful of sawdust from the spill bin, and mixed them up, thats it -simple.No more noise. Regards John.

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Just to let you know it's been back to Donnington again and Stuart Garner's team have worked some magic and the noise is all but gone. Apparentley the clutch basket has been modified and the difference is unbelievable, they have also addressed some other issues I had and the bike has been transformed. I only managed 50 miles on it yesterday as I had to go out with " 'er indoors" but had it not been for that I would have stayed out all day because I was enjoying the bike so much.

Hope if anyone is still waiting for their 961 get theirs soon but if its any consolation once you do get it they do seem to do their best to look after you.

Best

 


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