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Unusual noise

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Unusual noise

Postby srx600 » Tue May 17, 2022 2:47 pm

This is a bit of a newby question but I have a noise on deceleration which I am not sure is normal or not. When rolling downhill on a closed throttle there is a noise like an over tight chain, doesnt always happen but often enough for me to want to understand what it is. I have pulled the side case off and nothing seems wrong. Engine is a largely standard Li150, it has a standard tensioner and the chain does look to be at the end of its adjustment, but there is no obvious signs of the chain hitting the casing. No play in the clutch etc. The oil was black but no obvious metallic content. Does the cush drive on the primary drive make a noise when it slips ? (assuming it does slip)
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Re: Unusual noise

Postby Warkton Tornado No.1 » Tue May 17, 2022 8:19 pm

Having been around SIII's continuously since '73, I doubt that I would now utilise a standard tensioner in any engine, regardless of the state of tune.

I suspect the pace of life & riding styles have changed significantly since when the transmission design was conceived, but if there is the slightest tendency for modern day riders to apply dynamics & use the gearbox to full effect, then an upgrade is the safer option.

That said, a well engineered replacement tensioner will tend to permit additional adjustment in any case (excuse the pun :oops: )

To answer your question though, by your description, the stretched chain may be whipping. Upon deceleration, the bottom run of the chain goes slack, the top run being tight. Bearing in mind that the bottom component of the OEM tensioner is only a guide, perhaps you can imagine that the slack part of the chain will 'whip' about.

For around a tenner, a good 'metal with nylon' uprated tensioner can be bought. I know one piece nylon are available, but if I've had an engine to work on fitted with such like, my conscience has always dictated the addition of an additional support mackled up from steel channel.

With such a 'better' tensioner in place, the bottom guides should be dispensed with.....along with the chain if it's a Rolon ;)
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Re: Unusual noise

Postby hullygully » Wed May 18, 2022 10:44 am

could also be little end going, my TS1 once started making a whirring noise coming back from Shipston, I put it down to exhaust coming loose, then a mag brg wearing, then realised it was in the barrel :? rang a nice lady
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Re: Unusual noise

Postby hullygully » Wed May 18, 2022 10:45 am

cush drive slippiing sounds like your clutch plates slipping bud, happened to me again coming back from Whitby on my TV with a cheese made sprocket :shock:
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Re: Unusual noise

Postby srx600 » Wed May 18, 2022 9:55 pm

Thanks for the ideas, will check them out. Looks like I need to invest in a few tools.
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Re: Unusual noise

Postby Warkton Tornado No.1 » Wed May 18, 2022 10:38 pm

If you haven't already got Sticky's manual, it's highly recommended & simply a damn good read.

As you've figured out how to remove the crankcase cover, then you should be capable of removing the front sprocket if required. You may get away without doing so (to replace the tensioner) but it's best to check the alignment of both sprockets.

If there is misalignment, then the best way to correct that will be the clutch removal. With some ingenuity, a specific clutch compressor is not essential, but it is a good tool to have.

I think you may be best to first check the alignment of the sprockets, report back (or refer to Sticky's manual) & then make decisions.....though if you were wanting to upgrade the tensioner there is some sense in buying a clutch compressor, crankcase gasket from the same source. Just ensure that if swapping the chain, such brands as Cross + Morse, Iwis, Regina & Renold are all good & an industrial power transmission supplier will be a better source IMHO. 3/8" pitch duplex chain is really nothing just specific to Lambretta :lol:

As for oil, I've been using & fitting ATF in engines that I fettle for about a decade, but opinions vary on oils, in particular..... ;)
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Re: Unusual noise

Postby srx600 » Mon Jun 13, 2022 8:45 am

Update: - Having invested in the clutch tools and bough a new Iwis (80 link) chain the noise is now worse than before.
I checked a few things when stripped, there was quite a lot endfloat on the rear sprocket/basket so I added a 0.2mm shim, with a 0.3mm shim the basket would rotate but there was obvious friction, so a 0.2mm should be good (0.25mm would probably have been better). The front and rear sprockets were 0.7mm out so I shimmed the basket/sprocket to add 0.6mm (total 1.7mm). The chain is a new Iwis 80 link,(old chain is a Renolds 80 link), the only way it could be fitted was to remove the front sprocket, assemble chain and sprockets, and slide both the front and rear sprockets on together, once assembled there was around 6mm play in the chain. I bought a new nylon guide but found that in the lowest position the end was touching the rear sprocket, so I ended up putting the original guides back it.
The noise is a whirring noise which sounds like a tight chain, the rear sprocket looks to be the original series 2 item with a cush drive. The only thing I can think of is the sprockets are worn and dont like the new chain (old chain was at limit), for the time being I am going to put the old chain back so I can at least use it. Longer term I will get a new rear sprocket/basket and front sprockets. Still at least I have the tools now :-)
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Re: Unusual noise

Postby dickie » Mon Jun 13, 2022 10:50 am

I once built a gearbox and was perfectly happy with all tolerances. It turned absolutely fine.

A few weeks later I had it on the dyno at chiselspeed and it sounded like a bag of hammers. Martin said he wasn't happy running it on his dyno; I can't blame him, it sounded like it was going to explode.

Anyway, he stripped and rebuilt while I watched. He couldn't find anything out of tolerance, but there was wear on the layshaft and selector. He also didn't like the LI type clutch pressure plate that I was using
. He replaced all and it was perfect. But note that he didn't find an identifiable cause, and he's considerably more experienced than the vast majority of us.

All I'm saying is that tolerance stack-up can be a cause but is difficult to spot as it's not a single measurement.
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Re: Unusual noise

Postby Warkton Tornado No.1 » Mon Jun 13, 2022 4:10 pm

Having thought about any issues some more, I really should have empathised just why it is that the strong uprated top only tensioners exist. If you think about the ACW direction of travel, the lower run is constantly under tension except upon deceleration, where even racers will attempt to use everything available to retard the machine in any way possible. Brakes, gearbox & sitting up are all utilised in an attempt to slow the machine as drastically as possible prior to the next corner. Yet, somehow, the re-engineered alloy/nylon top tensioners cope under load extremely well despite the transmission chain loading reverting to the lower run in such instances. Having wandered around the pits & observed many fellow racers' engine strips over many years, I cannot recall seeing anything but the type I speak of. That's not to say there's not somebody using bottom chain tensioners in a race machine, but I very much doubt it...... ;)

Like anything associated with raising the overall performance of Lambretta, the uprated tensioners evolved & the first commonly available type was a cast alloy reinforcement that fitted 'beneath' the OEM top tensioner to stop it bending under the load of hard deceleration through the gearbox. Thankfully, the next logical iteration was the alloy/nylon top tensioners that have proved virtually bombproof. I am aware of the moulded nylon (only) top tensioners but that wouldn't be my choice for a hard ridden machine. In fact, whenever they have appeared on a bike that I have worked on, I always add some means of extra support, usually fashioned from a piece of Unistrut just to avoid any problems. Yes, sometimes I worry too much.... :roll:

As for your latest acquisitions, my thoughts about any necessity for a lower chain guide have hopefully been explained, but what we do to our Lambrettas is very much a personal choice, which I applaud. You just won't find any machine of mine with disc brake windows or handlebar tassels..... :lol:

To - hopefully - conclude, new chains are tight & do often require that both sprockets are slid into place in parallel, so I doubt yours are badly worn. Not unless there is an extra tooth in there somewhere. Quite why the new top tensioner can run into the clutch sprocket is a concern to my mind. It's almost as if somebody has sold you something not quite fit for purpose, an event unheard of in Lambretta remanufactured product sales..... :lol:

I'd suggest that having got this far (BTW. Well done!) & sussed out the misalignment & bought into the tooling, you trim the new top tensioner to obviate the clash & fit it with some means of additional strengthener beneath/on top (I've lost the plot!) & try that. Seriously, there is a 'safety factor' even here with a humble chain drive. Whatever you have new is likely to be many times stronger than the OEM tensioners so any risk of catastrophe is low. The new chain will bed in, so any whirring noise should diminish so that it sounds less like a V*sp@. If it does: CHAMPAGNE! That is, until the realisation that the chain will need tensioning a tad more. Good job you got them tools.... ;)
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Re: Unusual noise

Postby srx600 » Mon Jun 13, 2022 6:55 pm

Warkton Tornado No.1 wrote::
To - hopefully - conclude, new chains are tight & do often require that both sprockets are slid into place in parallel, so I doubt yours are badly worn. Not unless there is an extra tooth in there somewhere. Quite why the new top tensioner can run into the clutch sprocket is a concern to my mind. It's almost as if somebody has sold you something not quite fit for purpose, an event unheard of in Lambretta remanufactured product sales..... :lol:


It was an odd one, because the chain didnt require any adjustment the tensioner was sitting quite low down, if I lifted it enough to clear the sprocket the chain tension was to much. It was a mid-priced tensioner from a known manufacturer (not sure of the forum rules on naming companies)

Warkton Tornado No.1 wrote::
I'd suggest that having got this far (BTW. Well done!) & sussed out the misalignment & bought into the tooling, you trim the new top tensioner to obviate the clash & fit it with some means of additional strengthener beneath/on top (I've lost the plot!) & try that. Seriously, there is a 'safety factor' even here with a humble chain drive. Whatever you have new is likely to be many times stronger than the OEM tensioners so any risk of catastrophe is low. The new chain will bed in, so any whirring noise should diminish so that it sounds less like a V*sp@. If it does: CHAMPAGNE! That is, until the realisation that the chain will need tensioning a tad more. Good job you got them tools.... ;)


I dont really want to strip it down again just yet, how many miles do you think it will need to settle in and quieten down ?.
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Re: Unusual noise

Postby Warkton Tornado No.1 » Mon Jun 13, 2022 8:04 pm

srx600 wrote:
I dont really want to strip it down again just yet, how many miles do you think it will need to settle in and quieten down ?.


So, I am a bit confused now as to which chain is in. New or old?

srx600 wrote:
for the time being I am going to put the old chain back so I can at least use it
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Re: Unusual noise

Postby srx600 » Mon Jun 13, 2022 8:48 pm

Warkton Tornado No.1 wrote:
So, I am a bit confused now as to which chain is in. New or old?


New chain, original tensioners which weren't very worn and are set at the lowest position so not really touching the chain. I was thinking of putting the old chain back in, but if you think he new chain will settle down I will leave it. It also occurred to me that I am riding it without rear footboards and sidepanels which could be making the whirring noise seem louder.
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Re: Unusual noise

Postby Warkton Tornado No.1 » Mon Jun 13, 2022 11:53 pm

Hmm.

The original noise probably caused by the stretched chain (we think) has now been eliminated, only to be replaced by the noise created by the new, tight chain.

It may be difficult to be precise, but the two noises ought to be quite distinct.

The initial issue may well have been a cacophony but the current sound more of a whirring. If that is the case, it should reduce as the chain beds in. Let's hope it does & if it does, then is the time to fit the new tensioner as there should be some slack to allow for it.....Even if the top tensioner requires trimming etc. Presuming you fitted new, you should get away with filtering your oil. I hope you greased the gasket prior to fitting because, likewise, that may survive & be re-used.

Gasp! :lol:
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Re: Unusual noise

Postby Fast n Furious » Tue Jun 14, 2022 1:36 am

I drain my hot oil out strained through a paint filter and then wash the sludge with detergent to see what non ferrous particles are present. Determining what constitutes as normal, has yet to be truly determined however. :lol:
If say after a 100 mile you pull the drain plug and find the magnet covered in a grey sludge, then this would be normal for some new chains and sprockets but the next check at say 200 mile, should show a much cleaner magnet. If not, then something within the transmission is awry. :cry:
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Re: Unusual noise

Postby Storkfoot » Wed Jun 15, 2022 1:07 pm

Warkton Tornado No.1 wrote:Having thought about any issues some more, I really should have empathised just why it is that the strong uprated top only tensioners exist. If you think about the ACW direction of travel, the lower run is constantly under tension except upon deceleration, where even racers will attempt to use everything available to retard the machine in any way possible. Brakes, gearbox & sitting up are all utilised in an attempt to slow the machine as drastically as possible prior to the next corner. Yet, somehow, the re-engineered alloy/nylon top tensioners cope under load extremely well despite the transmission chain loading reverting to the lower run in such instances. Having wandered around the pits & observed many fellow racers' engine strips over many years, I cannot recall seeing anything but the type I speak of. That's not to say there's not somebody using bottom chain tensioners in a race machine, but I very much doubt it...... ;)

Like anything associated with raising the overall performance of Lambretta, the uprated tensioners evolved & the first commonly available type was a cast alloy reinforcement that fitted 'beneath' the OEM top tensioner to stop it bending under the load of hard deceleration through the gearbox. Thankfully, the next logical iteration was the alloy/nylon top tensioners that have proved virtually bombproof. I am aware of the moulded nylon (only) top tensioners but that wouldn't be my choice for a hard ridden machine. In fact, whenever they have appeared on a bike that I have worked on, I always add some means of extra support, usually fashioned from a piece of Unistrut just to avoid any problems. Yes, sometimes I worry too much.... :roll:

As for your latest acquisitions, my thoughts about any necessity for a lower chain guide have hopefully been explained, but what we do to our Lambrettas is very much a personal choice, which I applaud. You just won't find any machine of mine with disc brake windows or handlebar tassels..... :lol:

To - hopefully - conclude, new chains are tight & do often require that both sprockets are slid into place in parallel, so I doubt yours are badly worn. Not unless there is an extra tooth in there somewhere. Quite why the new top tensioner can run into the clutch sprocket is a concern to my mind. It's almost as if somebody has sold you something not quite fit for purpose, an event unheard of in Lambretta remanufactured product sales..... :lol:

I'd suggest that having got this far (BTW. Well done!) & sussed out the misalignment & bought into the tooling, you trim the new top tensioner to obviate the clash & fit it with some means of additional strengthener beneath/on top (I've lost the plot!) & try that. Seriously, there is a 'safety factor' even here with a humble chain drive. Whatever you have new is likely to be many times stronger than the OEM tensioners so any risk of catastrophe is low. The new chain will bed in, so any whirring noise should diminish so that it sounds less like a V*sp@. If it does: CHAMPAGNE! That is, until the realisation that the chain will need tensioning a tad more. Good job you got them tools.... ;)

What issue do you have with disc brake windows, WT?
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Re: Unusual noise

Postby Warkton Tornado No.1 » Wed Jun 15, 2022 2:39 pm

Storkfoot wrote:
What issue do you have with disc brake windows, WT?


Lambrettas often have had some form of embellishment.

I can see the point in having, say, GP side panel grills as they really do act as a protection in the event of an 'off' plus they do break up what is otherwise a very plain surface. So you'd be correct in assuming that my choice would not to be spending time & money filling in the recess' as others may wish to do.

TBH, although I can admire those that strive to recapture the OEM appearance of earlier SIII's than the GP, I'm not overly keen on the chrome ring between the legshields & the headset, so if I ever get around to rebuilding my 'D' registration TV200, I will have to investigate that particular item as to whether it ever had one - hopefully it didn't ;) Whilst on the subject of TV200's, mine came to me with SX200 panels, because that's what often happened. I doubt many would deny the SX200 panels to be by far the best as far as aesthetics, hence the roaring trade in the 'borrowing' of desired panels from scooters in the 60's/70's. That's why panel locks became a necessity. I also have a GP200 to rebuild & although I have several Italian GP headsets, but currently I prefer the look of the chrome ring seven sided (often referred to octagonal) TV etc headsets with the GP. Fortunately, I have quite a few of those as well.....Hoarding B@st@rd!

So when it comes to disc brake windows, I think the machine looks better without. TBH I've never fitted the brightwork such as panel or leg-shield scripts to any of my rebuilds, but that has been often due to the choice of paintwork.

The choice of the final look of a Lambretta comes down to personal choice & I would suspect that scooters were one of the first machines to be customised in the UK en masse....
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Re: Unusual noise

Postby Storkfoot » Wed Jun 15, 2022 4:12 pm

Ah, so no science behind it then :D

Personally, I don’t like to think of small rodents nesting in my hub so I keep them on :P
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