Bonneville America Forums Forums Technical Forums Performance Mods Idle Speed

Why is the recommended idle speed so high - 1000 - 1250 RPM I keep seeing.

I have always set gasoline engines at 650 to 750 - and the pipes sure sound funkier at that speed with the 270 crank.

Any thoughts?

I could be wrong, but I think some of it is to keep the oil pressure up.

Also so it won't stall when you go to take off. Those pesky CVK carbs are a bit finicky at low idle. I keep mine around the 1100 mark, maybe slightly higher. Kind of hard to tell actually, I do it by feeol, the tach is not very accurate at those low r's.
I tired keeping it down lower, sounds really nice with the slow lopping sound, but it would stall on me ocassionally. I don't want to give my HD buddies anything to mock you know.

editted cause I got fat fingers

The idle speed is like that because there is relatively very little flywheel mass on this engine. On the old Triumph twins, the entire space between the crankpins was a big round slug of iron to keep the engine turning between power strokes, but the new ones have a cam drive sprocket and a third main bearing there. It will idle a little slower than that, but without a lot of energy stored in a massive flywheel, the engine will stall very easily when starting off.
Another factor is that the carburators don't work well with the diminished air flow.

It's just as Triumphant says in my book. OIL PRESSURE. A lot of the Harley owners (and me with my old Ducati) like the "low, barely running, uneven, drag car like, idle" - but damage is occuring all the while! On my old Duke, when I tune it that slow it sounds great - but the LOW OLI PRESSURE WARNING LAMP keeps flicking on and off. The warning is set at that pressure by the manufacturer.....for a REASON!!!