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carb air flow way off
Posted: Mon Jul 29, 2019 9:44 pm
by sevenmilebridge
Front carb on my 1600 drawing lots of air rear carb hardly any air flow. Possible weak spring on piston?? very frustrating any thoughts
Re: carb air flow way off
Posted: Tue Jul 30, 2019 4:51 pm
by C.Costine
Have you checked valve lash yet?
Re: carb air flow way off
Posted: Tue Jul 30, 2019 5:03 pm
by greydog
Valve lash
Choke hanging up
Vacuum leak
Are you not able to balance air flow? Can you describe your process?
.
Dan
Re: carb air flow way off
Posted: Tue Jul 30, 2019 6:35 pm
by sevenmilebridge
Checked valves they are in adjustment. There is no vacuum leak. The difference is significant I haven"t run into this problem before. I"m about to tear out what little hair i have left.
Re: carb air flow way off
Posted: Tue Jul 30, 2019 7:10 pm
by greydog
I had a similar issue with our 1600. I found the choke cable was holding the front carb nozzle up a bit.
I loosened both choke cable clamp screws and used the "magic number" to set the nozzle heights. Once that was done, it was pretty close (within a quarter turn".
I like my snail for measuring flow, it's easier for me to read then a floating ball.
Sounds like you've been battling this for a while. You may be best off to start from a base line (that's the advantage of setting the nozzle in the body at a measured height).
Dan
Re: carb air flow way off
Posted: Wed Jul 31, 2019 10:59 am
by Gregs672000
It has to be a linkage problem. I suggest examining how the linkage works to adjust the carbs. I don't have fully stock linkage and found that the way I had it set up would not allow for the balancing linkage to work right (Dellorto carbs, so somewhat different set up), but it took really looking at what was happening to understand what needed to change.
I would disconnect the linkage between the two carbs and get each carb flowing the same air, then see what happens when you reconnect them via the balancing linkage. As I recall, both carbs have a screw that will directly move the throttle plate individually, so start there by getting them to flow the same, then address the balancing linkage issue. Think about it: One carb is not being allowed to flow the same amount of air, and the flow of air is determined by the carbs throttle plate only. Something is changing the position of that plate.
Re: carb air flow way off
Posted: Wed Jul 31, 2019 2:13 pm
by SLOroadster
Your carbs are out of balance. Balance the carbs with a unisyn and see how that works.
Will
Re: carb air flow way off
Posted: Wed Jul 31, 2019 8:01 pm
by jrusso07
As Keith at Roadster ranch instructs- take all adjustments to neutral- that is, loosen the chokes, loosen the throttle, loosen the balance screw turn the mixtures all the way in CCW. Then find initial setting s from the manual and start from there.
Else you aren’t pulling any vacuum on that carb due to a major problem - cracked isolator, bad cam...?1