How to tune air/fuel mixture?

55959 Views 45 Replies 15 Participants Last post by flitecontrol, Jun 17, 2021

chillywilly638

Discussion Starter · Mar 30, 2011

Hi
Well like the title states, how do you tune the air/fuel mixture. I heard I could tune it with an rpm gauge. If so how exactly? I've called a couple of places but they each charge like 60 bucks. I figure I could waste 30 on the tools and never have to pay anyone to do it again.
Thanks

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twitch

· #4 · Apr 2, 2011

HitCat44 said:
There is a tab that has to be removed if it hasn't been already that allows the A/F screw to be adjusted. If it has been rebuilt by you or another, the screw with the tab has been replaced by a straight end with blade type slot and non-tabbed one usually.

Okay, hang on, I'm confused. I tried to perform this idle drop procedure today; the instructions in my manual are nearly identical to the ones BuickGuy posted, except the number of turns for the initial opening is different for newer Rebels.

But...I'm supposed to remove this tab on the pilot screw? My manual doesn't say anything about that. Seems like that tab would be there for a reason, but I certainly can't turn it 2 3/4 turns while it's there. So I need to go out and get a normal screw that will fit? How can I unscrew it out of there with that tab in place? File down the tab?

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twitch

· #11 · Apr 3, 2011

Okay, so is it worth going to all that effort if I'm not having any performance problems? I was only going to do it because my service manual says it's a good idea if you don't know whether it has ever been done.

As of right now, I'm thinking of just leaving it alone unless someone convinces me otherwise. I found it set open as far as the tab stop will allow. My idle is about 200 RPM too high, but I can fix that with the idle adjuster.

If I understand what you all have posted, the stock is setting is government-mandated "too lean." What are the long-term effects of running lean? Engine damage? Poor mileage? Poor performance?

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twitch

· #19 · Apr 3, 2011

Guba said:
If I recall twitch, you bought your bike brand new. I wouldn't think mother Honda would turn it over to a dealership with something like that seriously out of adjustment. Extremely lean conditions will make the engine overheat and give less power. A hot engine can result in pre-ignition of the fuel/air mixture. I don't really think you have to worry about it until you have to take the carb apart. That is, unless you want piece of mind and just want to play.

WIN. I would do it just to do it, IF it didn't involve modifying a part that's there for a reason (even if the reason is just to make Uncle Sam happy). I'll wait until the carb needs service and I'll do it then.

Thanks to everyone for your advice.

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How to tune air/fuel mixture?

chillywilly638

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