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Advise on Carb. Specs #747812 09/03/18 9:46 pm
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Doug F Offline OP
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Hey All.
Been quite a while but finally getting the old 1966 Lightning back together & ready for Carbs. From all I've read & researched I'll go with the AMAL 930 Premier Concentrics.
Was reading another thread here about carb set up & got me thinking which size slider to order them with. I take it the 3 inch is for sea level & keeps it a bit richer.
I'm in Wyoming at about 5100 feet or more & plan to ride up into the hills quite often so I think the 21/2 inch is the better choice for altitude.
Any feedback & tips is much appreciated.



'66 Lightning Engine, '68 Mark IV frame "bitsa"
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Re: Advise on Carb. Specs [Re: Doug F] #747830 09/03/18 11:59 pm
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Shane in Oz Offline
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Don't you have to lean the mixture for higher elevation?

In that case, you'd probably need a smaller main jet and a 3 1/2 or 4 cutaway slide.

Burlen Fuel Systems should be able to give you some tuning advice, and may even have some technical details on their web site regarding tuning for altitude.

Re: Advise on Carb. Specs [Re: Doug F] #747870 09/04/18 8:47 am
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gavin eisler Offline
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Higher altitude means weaker settings, usually just the main jet goes down a size or two .


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Re: Advise on Carb. Specs [Re: Doug F] #747954 09/05/18 6:15 am
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C.B.S Offline
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You can try to prepare any carb for any elevation but at the end of the day a carb will have to be installed regardless of the correct or not correct jets in it . I like to install carbs and jet it to how it would of came from the factory. From there, you can tune it step by step. "predicting" carb jetting causes trouble at times because you may start working backwards.


Start with stock slide, pilot, and main jet and work up/down from there based off how the motorcycle is running


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Re: Advise on Carb. Specs [Re: gavin eisler] #748003 09/05/18 4:50 pm
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Allan Gill Online Happy
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Originally Posted by Shane in Oz
Don't you have to lean the mixture for higher elevation?


Spot on Shane

Originally Posted by gavin eisler
Higher altitude means weaker settings, usually just the main jet goes down a size or two .


Agreed,

930 (4 stroke) Concentric's on a 66 On Lightning should have:

no.3 slide
106 needle jet
needle clip in top groove
180 Main jet.

As Gavin said, drop a main jet size, the main jet has some effect from half throttle onwards (and runs solely on jet at full throttle) so there will be some/slight leaning off from half throttle also, more noticeable as you get to full throttle. With this in mind I'd fit a 170 main jet, it won't be overly noticeable if you drop below 4-5000 feet and if you go higher you probably won't notice too much it being a tad richer.

anything above 3000 feet takes effect, then for every thousand feet there is a change again. but if you find it is still too rich fit a 160, needle jet and all other positions should be correct AFTER you have sorted the main jet, working to the next jetting position down.


beerchug
Re: Advise on Carb. Specs [Re: Allan Gill] #748271 09/07/18 7:57 pm
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Doug F Offline OP
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Hey, Thanks for ail the good advice Folks.
I'll start with the stock slide & needle & main jet 1 size smaller & go from there. makes sense.
do 1 thing at a time
Was just trying to figure what extras to order with the carbs but certainly don't want to over complicate things
and this was the kind of info. I was looking for
Thanks All
and Allan for verifying the jets I figured I'd need to have on hand.

winter is coming fast here & i still have quite a bit to do on this ,
not sure if I'll get it running in time before snow starts falling & bitter cold.
may end up finishing this winter inside & firing up in the spring.


'66 Lightning Engine, '68 Mark IV frame "bitsa"
Re: Advise on Carb. Specs [Re: Doug F] #748369 09/08/18 4:17 pm
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Allan Gill Online Happy
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your welcome and good luck with your project


beerchug

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