Chain and guide

[gp200ts1]

Have a 82 link chain on 46-19 sprockets. Tensioner is a casa push up pull down. According to sticky’s spanner charts it should be push up but it’s pulling down. Chain isn’t worn as it’s new (iwis) and the same size as another new spare I have here. Is it a misprint in the manual or is something not right here.

[Warkton Tornado No.1]

Sprockets: Not only do they vary due to manufacture, they wear.

Distance from centres of crankshaft to clutch: I’ve never measured it, but I would imagine that there has to be some variation, specifically with those crankcases that arrive with a ‘dedicated end-plate’ by comparison with those of Innocenti etc manufacture.

Chain: The Iwis chain is highly rated by many in the automotive world. Duplex chain is used extensively in driving the camshafts in four stroke engines (timing chain) but unfortunately gets counterfeited as a consequence. Other Forums would appear to discuss the issue extensively. Ask yourself whether a ‘Lambretta Specialist/Dealer’ - that’s likely prepared to sell Rolon chain - is going to be more concerned about authenticity or their profit motive….


Out of curiosity, I wonder if your tensioner is of the type that utilises long slots - on the ‘blind’ side - that incorporate a shallow counterbored recess for the fastener heads? Recently, whilst clearing some of my cloud, I found images that I have retained, of one such a device that was incorporated in an engine that I rebuilt. The fasteners were brittle & had partly broken heads in several places. As per normal, I came up with a solution & fixed the tensioner as my conscience won’t allow me to turn a blind eye. Doubt I’ll ever get paid for my efforts, much like the rest of that whole build….

[gp200ts1]

I see what you mean by sprocket differences. I have a rimini cyclone engraved 19 tooth sprocket fitted and also have a cheap 19 tooth by an unknown manufacturer and it is noticeably smaller than the rimini one.

[gaz_powell]

Never had a problem with SIL rear sprockets and various make fronts # with Iwis chain on gp200 set up with 19x46x82 using various uprated standard type top guide and a standard bottom, never used push/pull type

# never used so called high end (bgm, casa etc) just what AFR have supplied me.. Though ive just bought an all MEC set up with deep rear to do a 5 plate (both sprokets and a new 82 chain)

Set several up on TS1 so its not a misprint, also same noted on AFR gear charts

Swapped a worn front sproket recently with an AF supplied unbranded, all okay with a slight chain adjust.
Was able to change sprocket by releasing the guide, leaving rear in place.

Stripped my last build earlier in year to check chain (MEC), showed a little bit stretch which was adjusted.

Never measured or compared sprokets sizes... Though would agree wear would play a part to some extent.

Best of luck with solving it

[Warkton Tornado No.1]

Anyway, all things being equal, though I’m clearly not the only one to be aware of manufacturing differences, we all should take into account that sprockets will be eccentric to some extent which will manifest in a tight spot. Any chain tensioner should be set with that in mind.

As for preferences in push or pull of such a tensioner, there hadn’t ought to be any great reluctance to utilise the pull…..if there is confidence in the product! I suspect that is not always the case, though there are advantages to the extra wrap such a set-up offers. The extra wrap means that both chain & sprockets should be subject to less wear, which is probably one of the reasons that camshaft timing chains are invariably of such geometry, the other being that it utilises less space.