Tilly's....some have a return line....some don't ?

[jcp52]

What is the reason that some diaphragm carbs have a return line and some dont? I was recently searching for a carb for an AC 292 lynx. The oem Tilly had a return line and the one I found in my stash didn't. Can you successfully interchange the two styles? Thanks

[King Kat 4]

One of the reasons for the return line was to keep cool fuel flowing through the carb to eliminate vapor lock. I've interchanged them without any problems. If you have a sled that is prone to vapor lock the return line may help but I've never noticed a difference.

[jcp52]

Makes sense , thanks