Single vs. Duel Carb

XduncanX · Posted: September 7, 2007, 1:01 am Post subject: Single vs. Duel Carb

Hey everyone, sorry if this is a stupidly basic question, but I was wondering what the benefits are between a single and a dual carb set up. I've been seeing manifolds that turn the dual carb setup on the 650 into a single and my father (who's been assisting me with repairs, ideas etc) has told me it may be a good purchase. His reasoning is simplicity, a single carb setup has less that may break. What are the disadvantages though? I'd rather not lose any performance for the sake of simplicity, and if you can fix one, in theory you can fix two. But other than the simple nature, are there any other benefits to a single carb, and what are the drawbacks to a duel carb, again, disregarding ease of repair problems.
Thanks,
Duncan

INXS650 · 650Rider Supporter Joined: Mar 22, 2007 Posts: 645

Single would definetly be easier, and cheaper. Only one set of everything, and only one to pull off and clean. No carb balancing required either. Harleys have run one carb forever. Carbs don't really "break" so it's not an issue. I think the dual carbs offer a little performance advantage if you are going to hop it up.

xsjohn · Posted: September 7, 2007, 7:18 am Post subject: Re: Single vs. Duel Carb

I always step in Dog Doo when I mention this…….With one carb there will be no balancing the heat with the right hotter cylinder.....I would be darn sure this was not occurring……..With 25 degrees higher temps on the right using the same carb for both would be a mess with no way of reconciliation ….No body believes this but that sure isn’t from lack of my warning…..I know people are doing it but have they checked….In the summer when temps are very marginal the right would be a furnace……Not for me…

John

cfinn1 · Posted: September 7, 2007, 7:49 am Post subject: Re: Single vs. Duel Carb

I agree with John on this one. The temperature difference between left and right is definately real and something that needs to be dealt with.

XduncanX · Posted: September 7, 2007, 11:14 am Post subject: Re: Single vs. Duel Carb

Is there a way of dealing with the temp difference with a single carb set up, or does that difference mean that you have to have dual carbs?

xsjohn · Posted: September 7, 2007, 11:33 am Post subject: Re: Single vs. Duel Carb

I have already determined that the right is running hotter by measuring the temps ........one carb leaves no room to play........

John

cfinn1 · Posted: September 7, 2007, 11:50 am Post subject: Re: Single vs. Duel Carb

Does having a carb on each cylinder allow you to acheive a smoother running engine since you can balance out the slight differences between each cylinder with the carbs? i.e. slight differences in valve settings, manufacturing variations, slight compression differences etc... Or when you balance the carbs are you really only matching the carbs?

ok so you can all stop laughing when I use the statement "smoother running engine" when referring to a vertical twin Smile

xsjohn · Posted: September 7, 2007, 12:01 pm Post subject: Re: Single vs. Duel Carb

From what I have found if you have a hot cylinder and both carbs are set the same once you warm it up completely to operating temps in essence the hot cylinder runs leaner than the cooler cylinder which in turn becomes a richer cylinder......Richen both cylinders the same and the hotter cylinder becomes happy but the cooler cylinder becomes to rich.......Having two carbs sure makes it easier to tend to each cylinder independently giving each cylinder what it needs when it is at operating temperature.........Sure has smoothed mine out and hopefully make it last longer.......More useable power also......I have kits for the BS34 and others will be coming soon..........

xsjohn

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