Top end set up?Help needed.

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
User avatar
monkey boy
registered user
Posts: 106
Joined: Tue Mar 17, 2009 9:38 pm
Location: Staines,Middlesex
Contact:

Hi all,just making a steady start on my winter engine build and could do with advice.
Spec will be Rapido classic 225,48mm clubman,30mil phbh 4.8 final drive
I'm looking for a nice easy to ride bike with a good spread of power that pulls nicely from lowish revs
I have both 58 and 60 stroke cranks that i can use.
I've have the top end in front of me and have been measuring it up and putting the info into the lambretta archives calculator and have the following

58 crank 0 deck height
Exh 163.84
Tra 119.94
Inl 145.32
Blow down 21.95

60 crank 0 deck height
Exh 169.5
Tra 128.51
Inl 141.77
Blow down 20.94

60 crank .5 negative deck
Exh 171.46
Tra 130.91
Inl 139.93
Blow down 20.27

So question is what would be the best option to acheive what I'm looking for and why?
I understand longer exhaust timings make the engine produce power at higher revs but am trying to relate what part the inlet and transfers play in the whole picture Ie longer/shorter what affect it has.
Also is it poss to put in a positive deck height on the calulator and how do you do it?
All help greatly appreciated.
CHEERS AL
goldeneye
registered user
Posts: 1037
Joined: Wed Apr 01, 2009 2:28 pm
Contact:

i run a 225 rapido classic on my rally scooter. 42 clubman, 30mm phbh, remote filter, mec-eur 58 stroke crank, 4.8 gp 200 gears/19/46 sprockets 82 link IWIS chain, T5 stator and an AF light flywheel. pulls great, good on fuel, good twos up and luggage. could easily pull a 20 tooth front, but just kept it 19 for when twos up. i ride it like a P200 i.e. wide open all the time. probly does 75mph-ish.
User avatar
chris2470
registered user
Posts: 135
Joined: Tue Apr 07, 2009 8:52 pm
Location: Cambridge
Contact:

If we assume that the exhaust port is a nice oval shape and at a diameter of approx 0.62% of the bore, then in my opinion none are ideal.
Option A could use the exhaust port raising 2mm.
Option C also could benefit from 2mm cut of the piston skirt, inlet side.
As Option C will also bring an increase in capacity this is the preferred option, for me.

I will probably get people who disagree but that's my two peneth worth.
Best Regards

Chris
User avatar
monkey boy
registered user
Posts: 106
Joined: Tue Mar 17, 2009 9:38 pm
Location: Staines,Middlesex
Contact:

Thanks for the help lads
Think I'm gonna set the barrel up on the casing and have a tinker
Cheers AL
Post Reply Previous topicNext topic
  • Information
  • Who is online

    Users browsing this forum: No registered users and 16 guests