# Air/Fuel Ratio gauges?



## dsbray (Jan 7, 2010)

As many of you have had the same problems, I too am getting a little frustrated with the jetting of my BF750.:aargh4: I am wandering if any of you have used these air/fuel ratio gauges to tune your atv's? _If you have did they work or are they overrated?_ Or what about the carb synchronizers that connect to the bottom of the carbs? Any Info good or bad is appreciated.


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## BleednGreen68 (Apr 19, 2010)

Air fuel gauges are expensive! Atleast the one my dad bought for his F250 was. If its the same gauges you are talkin about. I know on the early brutes they had a recall on them about the metering needles. We only did the recall or bulletin IF the customer complained about backfiring. They made the needles smaller in diameter to get more fuel in the carb at mid to high range. Thats all it will affect. If you got a prob with idle jetting you will need a bigger pilot jet. The brutes were 38's. I put pilot jets out of a 700 prairie in mine and they are 40's. I dont know exactly what kind of idle issue you are havin.


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## dsbray (Jan 7, 2010)

i have 144f and 148r with #40 pilots/slow jets. it idles great but from 13mph to 20mph it spits and sputters about 75% of the time. WOT is good not great but what really concerns/annoys me is after its under strain Example mud hole or alot of water it seems to get worse for awhile and sometimes if I get stuck in thick mud it wants to die so I have to baby it to keep it running. the gauges i was looking at was about $200-$300 bucks. oh and i have the stock needle back in it with 2 shims on each one, haven't tried the dynojet needles since i changed pilots, and a buddy of mine gapped the plugs from .20 to .60 and i gues i'm not all that sure what that does? does it run richer with the bigger gap?


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## BleednGreen68 (Apr 19, 2010)

Well without seein it i can really help ya. I do better if im actually workin on it. Does it do any better with the air box lid off? Got to see if shes runnin rich or lean first. How do yer plugs look? Black? Brown? White? Squirt some carb cleaner around the carb holders while you are runnin it at the rpm's when it runs like crap. You might have air gettin buy causing a lean prob. Also check yer float level. Thats one thing people overlook. Very important.


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## Muleskinner (Apr 24, 2009)

60 thou is too big of a gap. I am not near my manual so somebody else should chime in but most plugs don't gap that big. 25 to 35 thou is probably the range. A big gap takes more energy to jump and can cause misfiring (sputtering).


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## BleednGreen68 (Apr 19, 2010)

I belive .28 to .32 is better. Yea .60 is really high. Takes too much voltage to jump that high i think.


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## dsbray (Jan 7, 2010)

Yea, I kinda thought that seemed high but what do I know? the carb holders where just replaced due to a crack in them from takeing carbs on and off way too much! the BF only has 200miles on it so i would hope the floats are good is there different setting for those? My buddy who actully works at a arctic dealer pulled the plugs and said they looked good (brown i think he said) so thats why I'm not sure where to go from here. when you shim the stock needles does it run richer than dyno needle on fourth notch? sorry about all the Q's but as you can probably tell I'm getting a little frustrated. I do think i'm going to have to change that spark gap though!


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## BleednGreen68 (Apr 19, 2010)

I'd have to check my bf service manual to check the float level. I usually just get the float level with the base of the carb body. Thats a good place to start. If yer plugs are brown thats good. Yea the more shims or the higher you notch it the richer it will run.


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## Heath070707 (Oct 12, 2009)

The guage is a wide band a/f guage that monitors your a/f ratio. These are used alot dyno tuning and you should be able to get your bike jetted perfect with it. You will need to have a bung welded in your exhaust though. Or you could weld one on the rear of each headpipe to tune each cylinder. If you have the money I would do it, you would prob pay someone that much atleast to tune it for you.


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## dsbray (Jan 7, 2010)

Thats what I was thinking, otherwise i'd have to take it to a shop if i can find one that will even work on it! I was reading somewhere about the numbers to strive for is around 14? has any of you used one on a atv? So your talking about welding a bung right before the exhaust on the tailpipe, do they have to be the same distance on the tailpipe from each cylinder? or does it read it regardless where it is at on the tailpipe? I'm really temped to pull the trigger on this one!!!! My wife might even go for it if it gets me to stop talking about it! LOL!!


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## FABMAN (Dec 18, 2008)

Hay if you like bring it to my place this saturday and I can help ya. oh and you want to aim for 13! 14 is for the perfect world so it the temp drops like 2* it will start to detonate and thats not good.


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