07-30-2017, 09:09 PM
07-30-2017, 10:31 PM
07-30-2017, 11:39 PM
07-31-2017, 08:29 AM
doug t. is correct
i was tired last night.
or getting dumber your choice.
blueprinting the carb before you do anything would be helpful in determining pop off pressure.
but for purposes of generally answering the question flatbacks on alky will like around 7.5-9# pop off .
this is a good general area to start.
that's not written in stone , there's alot of variables in every carb adjustment but if the carb was built/modified correctly that should be the area you'd want to start at to get running..
carburator performance is controlled by all sorts of variables
i've listed a few below plus there are things that you can't control like the weather and fuel conditions.
So it is useful to know exactly what is done to your carb.
things like the inlet needle passage size , the passage size for the control needles , are the control needles modified (ie shortened or thinned) the inlet holes in the idle circuit under the welch plug, and the size of the inlet holes leading to both the idle and high circuits in the fuel reservoir are all part of deciding pop off pressure.
the fulcrum lever height adjustment also needs to be taken into account.
this is called blueprinting and is extremely useful in assuring good track results and carburators NOT being throw into the woods in frustration!!
this is a long drawn out process to determine all these factors.
far to long to post here but if you are interested in that sort of thing i'll be updating the carb post to attempt a step by step blueprinting instructional.
anyone seeing mistakes in my instructions should feel free to correct me i am not perfect!!
go here to read further
https://www.vintagekartforum.com/newreply.php?tid=1636
Save
Save
i was tired last night.
or getting dumber your choice.
blueprinting the carb before you do anything would be helpful in determining pop off pressure.
but for purposes of generally answering the question flatbacks on alky will like around 7.5-9# pop off .
this is a good general area to start.
that's not written in stone , there's alot of variables in every carb adjustment but if the carb was built/modified correctly that should be the area you'd want to start at to get running..
carburator performance is controlled by all sorts of variables
i've listed a few below plus there are things that you can't control like the weather and fuel conditions.
So it is useful to know exactly what is done to your carb.
things like the inlet needle passage size , the passage size for the control needles , are the control needles modified (ie shortened or thinned) the inlet holes in the idle circuit under the welch plug, and the size of the inlet holes leading to both the idle and high circuits in the fuel reservoir are all part of deciding pop off pressure.
the fulcrum lever height adjustment also needs to be taken into account.
this is called blueprinting and is extremely useful in assuring good track results and carburators NOT being throw into the woods in frustration!!
this is a long drawn out process to determine all these factors.
far to long to post here but if you are interested in that sort of thing i'll be updating the carb post to attempt a step by step blueprinting instructional.
anyone seeing mistakes in my instructions should feel free to correct me i am not perfect!!
go here to read further
https://www.vintagekartforum.com/newreply.php?tid=1636
Save
Save
08-02-2017, 07:10 AM
(07-31-2017, 08:29 AM)David Luciani Wrote: [ -> ]doug t. is correct
i was tired last night.
or getting dumber your choice.
blueprinting the carb before you do anything would be helpful in determining pop off pressure.
but for purposes of generally answering the question flatbacks on alky will like around 7.5-9# pop off .
this is a good general area to start.
that's not written in stone , there's alot of variables in every carb adjustment but if the carb was built/modified correctly that should be the area you'd want to start at to get running..
carburator performance is controlled by all sorts of variables
i've listed a few below plus there are things that you can't control like the weather and fuel conditions.
So it is useful to know exactly what is done to your carb.
things like the inlet needle passage size , the passage size for the control needles , are the control needles modified (ie shortened or thinned) the inlet holes in the idle circuit under the welch plug, and the size of the inlet holes leading to both the idle and high circuits in the fuel reservoir are all part of deciding pop off pressure.
the fulcrum lever height adjustment also needs to be taken into account.
this is called blueprinting and is extremely useful in assuring good track results and carburators NOT being throw into the woods in frustration!!
this is a long drawn out process to determine all these factors.
far to long to post here but if you are interested in that sort of thing i'll be updating the carb post to attempt a step by step blueprinting instructional.
anyone seeing mistakes in my instructions should feel free to correct me i am not perfect!!
go here to read further
https://www.vintagekartforum.com/newreply.php?tid=1636
Thanks Dave. Sure would welcome any blue printing info on small flatback carb specs for alky and gas.
Your right about bdc popoff at 20+. Steve O gave me a bdc tutorial a few years ago at Bakersfield and really helped me understand them better. There used to be a great bdc article on Mc Bob's website that I can't seem to find anywhere else on web. I started this thread to refresh my memory but would be a good opportunity for people to share carb info lost on other forum and Mc Bob's site.
Dean
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08-02-2017, 07:28 AM
08-02-2017, 09:18 AM
08-02-2017, 11:08 PM
WOW, if that's true i'll miss him. great guy. 
08-03-2017, 08:58 AM