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Re: Carburettor tuning

To: e_holm@c2i.net, alpines@autox.team.net
Subject: Re: Carburettor tuning
From: JACranwell@aol.com
Date: Mon, 24 Jun 2002 05:21:48 EDT
Espen,

After dismantling, it is important to adjust correctly, or you'll be running 
too rich or too lean. The carbs will also be out of balance.

The main adjustment is to the jet height, which controls the mixture. This is 
adjusted with the smaller of the brass nuts at the bottom of the carb.

Unscrewing richens the mixture.
Screwing tighter weakens the mixture.

The best way to get this right is to use a colour-tune, if you can get your 
hands on one. This allows you to see the colour of the combustion inside the 
chamber.

Failing that, you can get it about right by lifting the piston +/- 1mm. 
Engine speed should speed up a little, then settle.

You then need to balance the throttle openings between the carbs, either 
using a vaccum guage, or if not available by ear. You can get it about right 
using a peice of tube, with the air-filters off. One end goes in the air 
intake, the other close to your ear. Balance the throttle adjusters until the 
sound is roughly the same between carbs.

By the way, the larger nut around the jet adjustment is to retain and centre 
the jet. If the pistons are moving freely, then leave these alone.

Good luck,

Julian.

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