Mikuna HSR 42 Running Rich

[Bob Riffle]

Hey Mike,

I have a 2003 FXDX Superglide Sport. I put the Mikuni, Screamin Eagle Ignition, S&S Gear Driven 510 Cam, Rivera adjustable push rods, V&H Long Shots-only because they were $200, and Magnacor plug wires on the bike. For just bolt-on stuff, the bike runs a lot better-but rich. Is it all right to be a little rich? I rode the bike to Colorado last year and at over 11,000 feet the bike ran great- the same as sea level. I've seen your recomendation for this carb for bikes that have upgraded the bore. Any recomendations for my set up or leave it alone. I have done nothing from the box to the Mikuni.

Thank you,
Bob Riffle

I hope this coming winter I get my bike down there and have some engine upgrades down from your shop.

[Mike]

With stock heads and V&H long shots using stock baffles, the Mikuni could be rich as setup from Mikuni. It's OK to be slightly rich so long as you are not fouling plugs but eventually carbon build up could be an issue. Fuel milage should also be better if not so rich.

We want to be carefull on how we determine rich conditions. Plug readings are only reliable when done under a variety of conditions, loads, rpms, mph's and done so with consistant methods. A plug reading at one set of conditions could actually give completely opposit results at another set. Correcting a rich condition based on plug readings at one set could result in a dangerously lean condition elsewhere (seen this on Sportsters with drag pipe many times).

The dyno is the only real way to test several sets and then adjust needle, main and accel pump accordingly.

[Bob Riffle]

I appreciate your advise. I hope in the future we can work together and get this engine set up the way I would like it.

Bob

[Mike]

Looking forward to it!