Vega Airbox Mods

[Angry Bloke]

I'm just starting to carry out some of the Vega mods as detailed in Ken Herlingshaws Manual of Performance and Conversions And was wondering about the Airbox mods

He recommends making a new top hat baffle with 8 x 10mm holes to increase the flow through the filter ,this entails turning one up on a lathe or braising one together from 31mm dia tube ( the standard is 27 mm with 4 x 10mm holes )

So my questions are

A - Does anyone have a remade top hat going spare

B - is there any reason why drilling a number of extra holes in the standard top hat baffle would not achieve the same result

cheers

[Storkfoot]

Peachy, have you got a scan or photo of the page please. I can't find my copy.

What plans do you have for the engine?

[Angry Bloke]

Hi Paul - I've got your address ,I will send you a copy of the vega pages.

I have decided to drill out the standard plastic baffle . After spending a while looking at it, it became obvious that the limiting factor is the holes in the shroud / cover, so as long as the area of holes in the baffle is the same as the shroud, then it will work .
So I'm drilling another 4 x 10mm ,4 x 6mm and 6 x 3mm holes in it

Engine wise the box of bits I purchased had a complete set and vega and starstream internals in it so I'm going with the Starstream crank ,kit and gearbox with vega sprocket / crownwheel with a SH1/20 (so I can use the modified airbox) and modified standard exhaust .

I'm in no hurry with this one so hope to be on the road next year

Colin has got one now so its " Go Team Luna " down here

[Storkfoot]

Thanks, mate. I'm finally starting to think of building my engine too.

[coaster]

.................Colin has got one now so its " Go Team Luna " down here

Picked it up from Jim last night, it's a lot more solid that I thought it might be, probably good enough for a rustoration if it wasn't for the headset top, spine and tank being from another scooter and thus a different colour. Important parts are there like seat base and exhaust but several bits missing so I have an excuse for Wickstead at some point

[Angry Bloke]

Colin - give me a shout first as I have a few spares now

[Adam_Winstone]

An interesting thread.

Thing is, I built a similar motor for the 125 that I had in my Vega for my Euro Kelso trip, IOW and a few other reasonably long trips but performance is not dramatically better than a standard 75, albeit at much lower revs. Look at the performance stats of a J125 and you will still want more for the effort. 50mph is pretty much it, as it was for my pal's Cento (45mph) that I converted to J125 spec.

At some stage I still fancy playing with the TZR conversion piston that I bought many moons ago as I don't think the standard J125 rings will like it much if I look to raise the exhaust port, remembering that the J is of an era which liked low wide ports and low revs. Increasing exhaust duration on wide ports with brittle rings is a push home combination

BTW my air box also has an increased number of holes in the cover/face to increase air flow to the modified baffle. Exhaust also seems to be a factor.

Adam

[Angry Bloke]

Hi Adam - thanks for the input ...... Food for thought

I've modified the air box ,i had thought the baffle would be fragile but it's quite sturdy



The j set up does sound like a lot of effort for small gains but I started with just casings so I was as easy to go with it .
Was it any different through the Rev range ?

It would be interesting to hear any reports on the Parma Kit as it could be a better option over the larger J cc

Cheers
Peach

[Adam_Winstone]

The power delivery at rev range is very different between the J125 and original 75 and is probably the real advantage of this conversion, allowing for touring revs, rather than small road screamer (75). There is certainly more that can be done to increase the horses of the 125 but wide port does mean that the piston/rings become the weak link if you look to raise the exhaust port duration, meaning that a piston swap is a worthwhile consideration.

I guess that this all comes down to what you want from a Luna or J machine. One telling sign for me is the number of casings that I've found with damage to the endplate studs, which is a common damage area on 6-stud LI format engines but seems all too common on the 4-stud J/Lunas. Perhaps these machines really were not intended to be used as tourers, especially uprated tourers, as we would look to make them (or high power shorter trip machines). They seem reasonably good for the 'pop out for a pint of milk' use that they were designed for but asking too much more is pushing it.

Sure, they can serve as a longer distance machine, as proven by my Kelso trip and Rimini's Euro crossing exploits, and more's the credit to those who do push the boundaries

Your airbox mods look very neat and tidy.

Adam

PS - I'll have a look in my little black book to see what gearing I ended up running as the standard 75 was too short and the standard 125 too long. I remember going to the lengths of having an LI front sprocket machined for single row chain use (sprockets now available form Rimini and others) and having a half-link chain made to allow for the combo that I ended up needing.

[Angry Bloke]

^ Great reply Adam - Thanks

I'm just looking at gearing so access to your "little Black Book " will be invaluable

[coaster]

Colin - give me a shout first as I have a few spares now

Oh I will Peach

Colin

[bjhart]

Can anyone post up some images showing the full air box mod as per the tuning manual, I have a PDF of the Vega section but the diagram for the baffle mod is very feint. Also does this mod with re-jetting help on its own or do all the tuning manual mods need to be performed to get any improvement
I'm sure I did see some images of the air filter case and baffle mod but can't find them now....any ideas?

[bjhart]

Hi Adam - thanks for the input ...... Food for thought

I've modified the air box ,i had thought the baffle would be fragile but it's quite sturdy



The j set up does sound like a lot of effort for small gains but I started with just casings so I was as easy to go with it .
Was it any different through the Rev range ?

It would be interesting to hear any reports on the Parma Kit as it could be a better option over the larger J cc

Cheers
Peach

Peach
Did the air box modification as per the images work? Did you fit it to a standard 75cc iron barrel and if so what jetting did you start with?
Cheers
Barry

[Angry Bloke]

Hi Barry - I'm only now rebuilding the engine as a 125 so I'm not sure yet

I will posts details when its finished (although probably not until 2017 !)

[bjhart]

Ok thanks, I have bit the bullet... I have enlarged the cluster of holes to 5mm, added 4 extra 6mm holes on the back side and drilled 8 x 4mm holes in the end of the baffle....as much as I can do without removing the baffle. The plug colour was a good brown colour, I will take it out for a spin and see if the colour has changed... And give some feedback

[bjhart]

Well just with the air box mods, the colour of the plug lightened, so increased the pilot jet to 50 & main jet to 78...colour of plug looks good although I need to test it on a longer run with hills to see it it copes with inclines any better....certainly seems more responsive off tick over and not so choked.
Sadly the speedo isn't working so no before and after speeds, although I was really only looking to improve on hills in 4th....I think I will compete all the recommended mods from the tuning manual to try to optimise the performance.....but ill wait till the winter for those.

[Angry Bloke]

Barry - Have you joined the Luna forum or FB page ?

There is loads of good info in both

[bjhart]

Barry - Have you joined the Luna forum or FB page ?

There is loads of good info in both

I am on the Luna forum but could you post the link to the FB page or give the full name please?

[Angry Bloke]

It's " Lambretta Lui Vega Luna" on FB

[bjhart]

It's " Lambretta Lui Vega Luna" on FB

Cheers, I'm in