chain guide

[hendy]

I've just dry-fitted a 'performance' chain guide which I bought from eBay and is an obvious copy of the Cambridge green plastic one.

I have 18/47 sprockets.

the lower guide is pushing the bottom chain run approximately 4mm upwards (from the front to the centre of the run, but getting better toward the crownwheel)

If I leave it like this it will wear into the correct shape, but it seems like it should be no more than approx 1mm out to me. My gut feeling is that it shouldn't touch the bottom run at all.

Also, the rear end of the top guide is really close to the rear sprocket (less then 1mm, depending on how/where I tighten it up). This is easily fixed with a hacksaw and file.

is this normal, or have I just bought some crap and it should be in the bin. Maybe it's a 15/46, but it did say that it was suitable for 'all lambrettas'.

I've only had a lambretta for 2 months and i've already learnt not to buy anything from ebay (except 2nd hand stuff); it's quite amazing how sh1t it all is.

[bristolmod]

you can , and many do, run with the lower guide left out.

Your comment re the closeness of the top guide to the rear sprocket is a bit alarming- it shouldn't be anywhere near it IMO.

Can you post a pic please?

Chris

[joeswoonara]

Bit of a contradiction in terms there " Performance " and "Ebay" dont usually go hand in hand imho but if it helps, i personally dont run a bottom chain guide after i had one find it`s way into the gearbox ...........forcing me to change underpants before a normal change was due

[wurzel]

I've got one of the green ones in my serveta engine and it's nowhere near the crown wheel and as Bristol Mod says
a lot of people don't bother fitting the bottom guide but if you do from memory the chain should run straight
at the bottom,this is the reason for the bottom guide being tapered.
Beware of Cheap Chinese Chat as some of these guides have been known to detach from their backplates and
jam the sprocket or crown wheel

[hendy]

first photo shows general view of what i'm talking about, and the second shows a little more detail.

clearly the upper guide can't be left like that, but it would be easy enough to reshape. the lower one is obviously going to sap power and very likely put excessive stress on the chain.

to be honest, now that i look at these photos i feel like i've asked a stupid question; there is no way i could run it like this. i'll be ordering new ones from cambridge tomorrow.

anyway, just out of interest here are the pictures..........

[goldeneye]

that looks shite. throw it away and buy a MB top chain guide, leave the bottom one off, ive ran with just a top chain guide for years no bother. ive seen a mates bottom guide snap off and mangle itself around the front sprocket, locking the engine at 70mph. the skid marks on the road were nearly as big as the ones on his undercrackers. took two blokes jumping on tyre levers to get his front sprocket off

[gaz_powell]

Have a look at this from ScootRS

http://scootrs.com/moreinfo.cfm?Product_ID=1557

I have used the ScootRS top on bottom on builds and been happy but I have also used the MB type without a bottom guide and again been happy.

the green top guide is massive compared to the scootrs one - however as it is only a guide it could be trimmed - I prefer this one piece or the MB type over a normal top guide.

This type of bottom guide with a large 18 or 19 sprocket often shows this issue - I have in the past elongate the fixing holes to lower it at the front sprocket to get it running without the slight up lift at the front. My personal preference is to run a nylon bottom

My last build used a MB top with a nylon bottom slightly modified.

That current set up does need something doing

Be interesting to what the CamLam ones fit like

[hendy]

are there any uk suppliers of scootrs products?

[YAMLAM]

Worth pm`ing Corrado on here , he`ll have something to suit .(top service too)

[Minority]

I had to attack my ScootRS bottom guide with the dremel/file to get it to fit without forcing the chain up