Lambretta carbs on seagull 102

Horsley-Anarak · Post by **Horsley-Anarak** » Sun Jan 18, 2009 1:44 pm

Has anyone tried using Lambretta carbs on a seagull.

Am I wrong in thinking that increasing carb size is an easy first step in tuning.

In the distant past when we wanted our cars or motorbikes to go faster the first thing that you would do was to swap to a bigger carb. Swap to 1 1/2" instead of 1 1/4" SU. Or on a Ford you would use twin choke Webbers. There were manifolds available and all sorts of different combinations.

A mate of mine had a 200cc Lambretta, which he stuck a 30mm Dellorto on. that made a huge difference to performance (2 up along the M27, could have done with a steering damper). That was the only thing that was done to the engine and it worked well.

There are various ones on the bay, Item number: 180321726442 looks quite good.

H-A

woodbutchergraham · Post by **woodbutchergraham** » Sun Jan 18, 2009 9:06 pm

Having some thoughts about this sort of work myself. I keep bouncing the idea about of ether a ram air system like the old Suzuki 380/550 or a small turbo or supercharger!.
I think, and hope to be put right on this one. It is the task of forcing as much air and fuel into the intake (if you can get more in you get more out ) I think thatâ€™s how it works
any one else have some ideas?

rosbullterier · Post by **rosbullterier** » Sun Jan 18, 2009 9:47 pm

Might a 28mm throat be a bit of a step up to fit a 16mm stub?

pistnbroke · Post by **pistnbroke** » Mon Jan 19, 2009 2:27 am

well well well and you all laughed when I put a Suzuki carb on from a 200cc outboard.......

Problem is as I see it is that due to the piston being the induction timing device ( rather than a reed valve or rotary valve) the air flow is highly pulsed and the suzuki carb did not like it . I could not raise the float high enough to give good suction on the jets......have the viking mower carb on at the moment

done the SU and the Webber ..still got the jet books !!!

rosbullterier · Post by **rosbullterier** » Mon Jan 19, 2009 9:54 pm

How's the search for the Amal 2-jet?

pistnbroke · Post by **pistnbroke** » Tue Feb 03, 2009 1:00 pm

here we have a number of pit bike carbs advertised ..they are much lile amal with a slide for the throttle etc ...the 49cc ones may be ok as they only engage the clutch at 5500 rpm so the 100cc seagull will pull the same air volume at say 2500...there is also a 125 carb with a 20 mm outlet throat for cheap money which may fit ..Iam investigating ...use the jap carb for day to day running and keep the amal for authenticity...

Collector Inspector · Post by **Collector Inspector** » Tue Feb 03, 2009 2:02 pm

Interesting all that!

Thing is when "plonking Bigger Carb" on "Old Dears" you generally run into all sorts of problems (Some mentioned above)

Carbs are quite unique for what they were designed for, that is why they worked so well in that reading plugs and idle speed adjustments just worked out to be pretty cool from the book.

Now, you say, "I tweaked the Be-Jesus Out of the Engine" and need a bigger carb?

Not necessary So!

Sometimes a smaller one works better.

Do air speed calcs.........................and look back to previous posts.

I have found that porting and piston mods are the best way of getting extra "Performance" (SIC) using a bog stock, out of the box, clagged on the side, original Carb with standard settings.

The Old Boys did know their stuff!

All much fun But!

Regards

C.I.