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Vega Airbox Mods

Technical help for Lui, Vega, Cometa, J50, Cento, J125, Starstream.

Vega Airbox Mods

Postby Angry Bloke » Mon May 16, 2016 5:05 pm

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 :D
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Re: Vega Airbox Mods

Postby Storkfoot » Thu May 19, 2016 9:56 pm

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?
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Re: Vega Airbox Mods

Postby Angry Bloke » Fri May 20, 2016 9:23 am

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 :D

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 8-)

Colin has got one now so its " Go Team Luna " down here
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Re: Vega Airbox Mods

Postby Storkfoot » Fri May 20, 2016 2:40 pm

Thanks, mate. I'm finally starting to think of building my engine too.
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Re: Vega Airbox Mods

Postby coaster » Sat May 21, 2016 8:34 am

Angry Bloke wrote:.................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 8-)
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Re: Vega Airbox Mods

Postby Angry Bloke » Sun May 22, 2016 5:36 pm

Colin - give me a shout first as I have a few spares now ;)
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Re: Vega Airbox Mods

Postby Adam_Winstone » Sun May 22, 2016 10:04 pm

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.

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Re: Vega Airbox Mods

Postby Angry Bloke » Sun May 22, 2016 10:47 pm

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

Image

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
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Re: Vega Airbox Mods

Postby Adam_Winstone » Tue May 24, 2016 10:18 am

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 :D

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.
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Re: Vega Airbox Mods

Postby Angry Bloke » Tue May 24, 2016 4:45 pm

^ Great reply Adam - Thanks

I'm just looking at gearing so access to your "little Black Book " will be invaluable 8-)
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Re: Vega Airbox Mods

Postby coaster » Tue May 24, 2016 11:30 pm

Angry Bloke wrote:Colin - give me a shout first as I have a few spares now ;)


Oh I will Peach 8-)

Colin
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Re: Vega Airbox Mods

Postby bjhart » Sat Aug 06, 2016 8:40 am

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?
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Re: Vega Airbox Mods

Postby bjhart » Mon Aug 08, 2016 4:21 pm

Angry Bloke wrote: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

Image

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
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Re: Vega Airbox Mods

Postby Angry Bloke » Mon Aug 08, 2016 4:37 pm

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 !)
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Re: Vega Airbox Mods

Postby bjhart » Mon Aug 08, 2016 5:11 pm

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
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Re: Vega Airbox Mods

Postby bjhart » Mon Aug 08, 2016 7:54 pm

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.
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Re: Vega Airbox Mods

Postby Angry Bloke » Tue Aug 09, 2016 2:08 pm

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

There is loads of good info in both :idea:
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Re: Vega Airbox Mods

Postby bjhart » Tue Aug 09, 2016 4:03 pm

Angry Bloke wrote:Barry - Have you joined the Luna forum or FB page ?

There is loads of good info in both :idea:


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

Postby Angry Bloke » Tue Aug 09, 2016 8:40 pm

It's " Lambretta Lui Vega Luna" on FB
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Re: Vega Airbox Mods

Postby bjhart » Tue Aug 09, 2016 10:16 pm

Angry Bloke wrote:It's " Lambretta Lui Vega Luna" on FB


Cheers, I'm in :D
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