Geabox noise

[Guest Nigelstephens]

I replaced the straight-cut gear box on my Sport 1100 I last year and obtained a centauro box from Reboot spares.

 

The box was very quiet in comparison to the original and this was badly damaged with the usual damaged bearings and gears with chips of metal in the oil.

 

The current Centauro box is getting a little noisy for my liking and I'm anxious to catch anything early. When I'm going along at 30-40mph the sound of the gearbox whine is nearly as loud as the engine. I'm sure this is not shaft drive or rear box related.

1. My first question is, is this a normal level of noise?

 

I have had some problems with clunky gear changes when hot and this could be clutch problems. This strengthens my case to get down to it and take the whole thing apart.

 

2. If I were to break open the box, do I need any special tools?

 

My intention would be to replace most bearings/seals and re-shim the box..

 

Many thanks

Nigel

[Guest Nigelstephens]

Come on you experianced gearbox fixers. Please help!

[Richard]

As far as I am aware there are no special tools required for taking the gearbox apart, but beware, the selector drum will need re-shimming when you put it back together (this may be the cause of any poor shifting at present - apparently the factory was terrible at shimming the 'boxes when new). You will need to disassemble the 'box in neutral to clear the selector drum/selector arm. I have not heard of any especially loud gearboxes with the helical gears - the straight cut are very whiney. Sorry I can't be any more help.

 

Richard

[pasotibbs]

Is it noisey in all gears or just top ? only under load ?

I seem to remember that the early 1100 Sports had an issue with the case hardening on 5th gear ?(I know your using a Centauro box but with Guzzi you can never be sure )

[Guest Nigelstephens]

Its noisy in all gears. I have found a wonderful article by Pete Roper on reshimming the box and from what he describes I definately think my box could benefit from this as first to second is always difficult.

 

Does anyone have a view on whether oil seals should be replaced. The output shaft is perfect but some would say to replace anyway as its easy to do and might as well when its apart.

[Mal]

Hiya

 

The 5 speed boxes are fairly simple to pull apart, its been a while since I did one but definately replace the seals/o rings while its all apart, its easy enough and they aren't too expensive and a bit of a ball ache to get at if they start leaking when its back on the bike.

 

I think you also have to replace the output nut as its pegged/hammered/dented to stop it undoing itself, also if you take off the input nut (at the front of the gearbox) you'll need a pegged washer (and possible the nut if you have to butcher it off - they can be VERY tight, mind you they have to be, I had one come loose once - very messy).

 

I'm sure Pete Ropers words of wisdom on shimming mention everything you need to do.

 

Good luck

 

Mal

[Guest Nigelstephens]

Thanks Mal.

 

I have got to the shimming stage now.

It took ages to get the clutch end nut off. I made a tool out of a socket by grinding out 4 pegs. However, I had bashed the nut so much it wouldn't take purchase. I found a very quick solution. Drill a small hole in the nut. Then slowly go up drill sizes and hey presto, tap it with a hammer and chissel and it came loose.

I do have a replacement nut and lock washer though.

 

For the shimming I ordered two of each size. The original selector did have movement laterally but after I found the correct new sizes the gap I can deduce at being about 6thou (no gasket).

So with a nice tight drum I face the decision about which way to move the selector drum for best gearchanges. Unfortunately the visual inspection through the filler hole does not concur with the wear on the selector forkes as far I can interpret Pete Ropers excellent article.

 

The selector fork of the 1-2 gear shows more wear on the 1st side. The clearance through the hole is quite a bit bigger between the dogs on the 1st side. The two methods of adjustment therefore suggest opposites when it comes to adjustment. That is, the visual clearance suggests moving the selector drum away from the engine end to make the gap more even between 1-2 for the muf when in neutral.

The wear method suggests that the selector should be moved towards the engine end as there is more wear on the 1st gear side of the selector forlk than on the 2nd gear side.

 

I think I will go with the visual inspection method and put the wear down to selecting 1st gear. This always clonks. As an aside could this then be caused by draging clutch or is it normal for 1st to clonk when engaging.

 

Now I can see why when selecting neutral from 1st at traffic lights might be difficult. I typically end up in 2nd then have to tap it down slightly into neutral. The fact that the muf is more towards the 2nd gear when in neutral suggests that this is the cause of this problem.

 

As for the poorer changes when the box gets hot this could again be clutch or could it be the more lateral play from the selector drum. The box is made of aliminium alloy and the selector drum from steel. So the box will grow longer slightly more then the selector increasing the gap from 6thou + 5thou (gasket) + expansion through expansion. Is this sufficient to move selector forks enough to cause me problems. Judgeing from the quite large travel of the mufs, I just cant see that this would cause clunky changes. Sorry Pete. But I have no experiance until I get it back on the road.

 

(Added Later.....

Have got the box back together and I found that a small change to the shims makes a large differance on the selector forks. I ended up with a 40thou shim one end and 50thou rubbed down to 46thou on the other end. The extra 6thou from the orginal 40+40, closes up the lateral movement and makes the muf exactly dead centre between 1st and 2nd cogs.

)

After inspecting all the bearings I found all to be in okay condition except for the main clutch shaft bearing. This did seem slightly noisy when I rotated it in the bell housing. Although a lot of metal to amplify the sound. I decided to change it anyway, including the seal.

 

The condition of the helical gears is slightly worrying. Most are okay however the single gear on the clutch shaft shows some pitting/cavitation on a few of the teeth. This can only get worse but could take along time. I decided to ignore and cross my fingers. I hope that is the right decision.

 

The last thing I will do before reassembly is to grind a bit off the tip of the spring loaded drum locator. I'm not sure if this will benefit a box of this comparitively young age but I dont think it will do any harm.

 

and gess what, I lost the ball that goes in the speedo drive. Too easy to do.

 

For tools I used just those in my garage. Nothing special.

 

Sorry for the long message but it might benefit someone else contemplating the same job.

[Guest Nigelstephens]

Just to complete the story, I got the Guzzi back on the road after 14 hours work.

 

The noise is very very much less so the main clutch shaft bearing was the cause.

After shimming gear changes are much better and I would recommend this to anyone with clunky gear changes.

 

In short, a good result and well worth the time and effort.

[pete roper]

Sorry Nigel, I completely missed this one. Hopefully you found all the info you needed in the gearbox strip article? When ou replaced the input bearing did you also replace the output shaft one? This is always a good idea, as is using AC3 bearings as these have more balls per race and a serpentine metal cage rather than the plastic cage of the bearings Guzzi chooses to use for cost purposes.

 

Pete

[Guest Nigelstephens]

I contacted two suppliers in the UK and the only ones I could get were plastic cage. So no unfortunately.

I did not replace the output bearing as it felt okay.

I will keep a close look out for any other problems but not hoping to find any. Just loving the enjoyment of riding the Guzzi with slick change for once. Thanks

[guzzijack]

I contacted two suppliers in the UK and the only ones I could get were plastic cage. So no unfortunately.

I did not replace the output bearing as it felt okay.

I will keep a close look out for any other problems but not hoping to find any. Just loving the enjoyment of riding the Guzzi with slick change for once. Thanks

 

Nigel,

 

I've just picked up on this one as well - sorry. There should be no problem in obtaining the 'good' bearings from any major UK supplier - try NSKs from WYKO http://www.wyko.co.uk/. Specs of all the seals and bearings are on Jen's website in the technical section http://www.guzzitech.dk/english/index.htm with generic bearing codes. The plastic ones are shite and will succumb again sooner rather than later - the 3205 AC3 (JC3) are the ones to fit.

 

Deffo a good idea to also replace the output bearing as, IMHO from the 'boxes I've taken apart, that seems to be the one that gets hammered a bit more than the input side. Maybe due to more lateral force on the shaft due to the proximity of the UJ? Input and output seals are different even though dimensionally they are the same - 35x47x7 - Viton (brown) for the front rotation but don't use it in the rear cover otherwise oil can piss out!

 

I had the clutch actuating rod thrust bearing go out on my V10 'box and that gave symptoms of progressively bad engagement as the 'box got hotter.

 

Bit late now and not wishing to appear a smart arse, but it was probably better to post this on one of the forums where the 5 speed box is more likely to be in use (COG, Guzzitech etc) Anyhow, well done on the shim job

 

GJ

 

BTW. I have a set of Rolf's special sockets here in the UK and could always loan them to you if you need them in the future - just PM me.

[Guest Nigelstephens]

Thanks for the info. Unfortunately, time pressures meant I had to make a decision and I chose the only bearings available from a Guzzi dealer. I use the Sport most days except when frosty or snow has fallen.

 

These bearings are the plastic cage type and I asked the dealer if alternatives were available. The response was that no others were available and all Guzzis use the same bearing even new ones so nothing to worry about.

 

I did a search on Google for the AC3 bearing number and ebay in the uk, but came up with nothing. In hind-sight I wish I had taken more time to search.

[raz]

Hi Nigel, you seem to be one or two steps ahead of me all the time. My16M, fork oil change, gearbox...

 

My question for now is, did you remove the engine for this or did you get to the gearbox just by removing swingarm and some other stuff? I saw a picture somewhere of an 1100 Sport with the rear end of the frame tilted upwards. On the other hand, it probably isn't too hard to separate the whole engine from the frame. In my case it's more a matter of workspace, housing the bike in my livingroom

[mike wilson]

Thanks for the info. Unfortunately, time pressures meant I had to make a decision and I chose the only bearings available from a Guzzi dealer. I use the Sport most days except when frosty or snow has fallen.

 

These bearings are the plastic cage type and I asked the dealer if alternatives were available. The response was that no others were available and all Guzzis use the same bearing even new ones so nothing to worry about.

 

I did a search on Google for the AC3 bearing number and ebay in the uk, but came up with nothing. In hind-sight I wish I had taken more time to search.

 

FYI, BSL (Bearing Services Ltd) is on the Team Valley Trading Estate. If you are ever stuck for a bearing PM me, as I live no more then 10 minutes from the store.

[Guest Nigelstephens]

Raz

I crabbed the frame. It takes about 1.5 hours to do. It entails removing the exhaust, swing arm, cowlings, tank and pork chop alloys. Cut cable ties and unbolt frame where necessary. Then can pivot sub frame up and on top of the front frame.

 

need a system to support the bike though. I used a combination of car jack wood blocks and axle stands.

 

This then exposes the back of the engine for the gearbox to be removed from the frame. It is necessary to loosen the two main engine mounts at the front to allow the engine to pivot slightly.

 

Thanks Mike for the bearing source. Will know for next time.