Hi all-

I started my freshly modded vanguard 23 hp backwater long tail today for the first time. Its mean, heads, exhaust and carb, it sounds great.

However I am having some issues with the idle adjustment. The tuning instructions might as well be greek to me and I have been adjusting two screws on the carb. One for air/fuel and the other for what I believe lets extra air in by adjusting the throttle slightly.

I can start the engine and it runs when the RPM's are above 1800 and the RPMS tend to go up on their own. The manual says not to go above 1200 for idle so when I try to dial it down to under 1200 for idle the engine runs for a minute and then kills itself.

any thoughts on this?

Also, I would like to add that I am running just basic unleaded fuel right now...does 91+ octane make that big of a difference?

When you crank your engine, it needs to warm up a bit before adjusting the carb will do much to dial it in. It can warm up at 1800 rpms. Once that's done then you start tuning. Adjust the air/fuel screw first one direction until it starts idling down, then go back the other direction until the same thing happens. Split the difference. Should be somewhere near 2 turns out from fully seated.
Now, adjust the idle rpm screw to get the idle rpm in the right spot. Little bit at a time until the rpms settle. It's not an instant response thing.
Just because there's a max idle rpm doesnt mean you should set it as low as possible. Set it somewhere between 1050 and 1150 and leave it be.

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