series 2 engine casing

[Scoot655]

have an early series 2 engine case that has all M6 threads around the cover side.Was wondering at what point they changed two of the threads to M8 to take the exhaust bracket and that is this too rare a case to modify to take an RB20 set up?

[Digger]

Probably not that rare - I've got a Series 1 that had the same.

What you won't have is the dished edge in the casing for the oil throw washer which would be more a decider for a performance engine.

I've had it converetd by Oiltek to the 200cc stud pattern, this included the studs for the exhaust go9ng out to 8mm so a stock or mild tune should be ok.

[a-teamlambretta]

I have just built an engine using a series 1 case and an imola top end, 62/116 crank(machined out the case for the crank) . I have used a sealed bearing for the drive side and left both seals in place, as the bearing is a sealed unit I cant see any reason for removing them so the oil throw washer is not needed now (not that it had one being a series 1 case). the only worry I had was the m6 studs used for the exhaust as I will be using an expansion pipe of some sort , did notice that there is more meat on the upper stud casting and might be able to go to m8 on that one and would probably be able to go m7 on the other as a compromise . but if running a clubman and you have the extra fixing point on the underside of the case you should be fine.

getting back to the sealed bearings , I use lots of bearings in my grinding machines and usually change them every year , they are subjected to some harsh conditions hot /cold, coolant contamination extreme loading . the grinders are usually running 8hrs a day 6 days a week (with a bit of luck) and very rarely get bearing failures . I always use skf or fag bearings but have tried some cheapos same size as lambretta front hub bearings as liner guide rollers on one machine and these have lasted the year.

[Wack]

One of the main problems with the early casings is the sidecase can break on the internal kickstart shaft housing,thats why Ser3 have external ribs.

[Scoot655]

many thanks for all the replies, feel better now about using it for an RB20 build. Will do the M8 threads myself but will get a tuner to match the case and barrel and sort any clearance issues with a new crankshaft. Best get the heater on in the garage then eh!?

[a-teamlambretta]

thanks to the captain for this info,


The bearing will be ok if you don't Rev it too high, the grease makes the bearing run hotter than if the same bearing is run in oil. This limits the maximum rpm that the bearing can run at.

The engine temperature again limits the capacity of the bearing running in grease, I think the limiting temperature is around 100 degrees C.
I would guess the lambretta bearings could easily reach a temperature very close to this.

I'm not trying to be smart or be the prophet of doom it's just that I've read the specs for Lambretta replacement drive bearings both in oil and double sealed in grease and the rpm is greatly reduced.

If I can find the info I will try and send you a link, I did once have a copy of an FAG bearing catalogue that I've loaned out I'm certain the info is in there.

All the best, Mark.

Ok I've had a quick look on the web and found some info that is close to some of the info I was referring to.
please read this and look at the maximum rpm of the double sealed 6305 bearing
https://www.motionindustries.com/produc ... u=02464098
Then you have to remember that the RPM limit is further reduced with heat.

will be removing the seal in my imola . thanks simon