LCGB Forums

Can anyone tell me if there is a specific amount of spline that should protrude out of the cone on a series 3 layshaft,,as I see you can but various thickness shims.

I have fitted a 200 Muggy and it came with an inlet manifold,but the carb isn't sitting level,its on quite an angle,which doesn't seem right to me.

Many thanks.

If the splines reach almost through the hub, then you have enough. If the splines are level or protrude the you have too much. The hub cone fits with the slot over a spline. I didn't think the shim under the cone varied however there are various shims at the gearbox end to allow adjustment.
What carb are you using? A slight tilt on standard carbs is ok.

Pete

hi Dave
carb at an angle is a very common problem. some manifolds are ok when series 1 & 2 engine mounts are fitted but on series 3 they can be miles out, over the years i've had to "mod" several manifolds with this problem. if you are lucky the holes can be enlarged a bit but i prefer to do a "cut & shut" job on the manifold to bring the carb away from the mount so that the carb can be rotated a bit to get it on or off.

Hi guys,sorry,it 26mm Dellorto.I will post a pic later,of the carb and the splines.

Here you are.What do you think?

hi Dave
i thought you were talking about a standard carb manifold.
i've never understood why a big carb is fitted at such an angle and refuse to do it on my scoots. surely the float bowl is going to have very little fuel in it. i've made my own manifolds so that carbs are upright and level just like the original ones were.
i'm sure there is a perfectly sound reason for mounting it on the angle and a qualified engineer will be along shortly

I agree,its not right is it.Some modification is needed.Or can a new manifold with less angle be bought?

The angle of the carb is exactly how they've been running perfectly for decades, using the down-draught application that they've been designed to run at and return a more efficient and direct path into the engine. This was designed into the design of your carb and allowed for by Dellorto.

Check out page 5 of this manual, which illustrated that you could actually run considerably steeper (40 degrees) if you wished (page 5):

http://jonathanvingiano.com/misc/dellorto-manual.pdf

Rimini do one that brings it out more square. Mito Lambretta also used to do one with a flange mount.

Bit of down draft is pretty standard with bigger carbs though.

Adam,just downloaded and printed that manual.Thats very interesting,will give that a good read,thank you.

thanks Adam for the info, knew there must be a reason for doing it

The manual should put your minds at rest if you are concerned about function at that angle but that's not to say that these carbs can't be run at a lesser angle. Indeed, the new Rimini PHBH manifold has already been mentioned and I actually run a modified ScootRS manifold on one of my motors, where having the carb at a more 'normal' angle/position suited my specific needs.

That said, I like to tinker so that specific manifold is modified for use with a solid mount PHBH 30mm. Another favourite of mine is to machine the PHBH CDC type down-draught manifold to improve carb/panel clearance so that I can fit and run a remote filter and standard side panel. I have a job leaving things alone, rather, I'll tinker until I end up with something bespoke that serves my needs better.

Regards,

Adam

I have often wondered about that illustration in the DellOrto manual. I guess that DellOrto were thinking of carbs that sit in in-line on motorcycles. They perhaps didn't think that some people might bolt the carb onto the side of the engine. If you were to lean into a long right-hander, the carb might be much more than 40degrees. Would this be a problem at full throttle?

Well, probably not. I think some 1970's Lambretta racer would have identified the problem whilst negotiating Gerrards at Mallory Park by now.

Angle of lean on a solo, 'side-draft' or not, is not a problem as centrifugal force (centripetal, actually) counteracts that angle. Think about your fuel tank just filled full to the brim. It doesn't slosh out the breather whilst negotiating a tight bend, does it? Incidentally, I believe that's why 'our' caps have the breather handle going from left to right, rather than front to back, just as a theoretical ideal.

A 'sidecar combination' would have problems with starvation or surge, which is why such devices as 'swirl pots' exist, but although used on the large wheeled variety, I cannot recall seeing their use on a scooter 'sidecar combination', racing or otherwise.

Thanks for all your replies.It seems that the carb will run quite happily at that angle,but,it just doesnt look right,so I have ordered the Rimini manifold.Will post a pic when it arrives.