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Old 12-22-2012, 03:00 PM   #1 (permalink)
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96 Indy Storm 800

I just pickd up a 96 indy storm 800 it fires right up but when you turn the choke off and give it some throttle it bogs down and backfires. Runs fine when the choke is half on any suggestions on what is wrong?

Any help would be much appreciated
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Old 12-22-2012, 03:15 PM   #2 (permalink)
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I just pickd up a 96 indy storm 800 it fires right up but when you turn the choke off and give it some throttle it bogs down and backfires. Runs fine when the choke is half on any suggestions on what is wrong?

Any help would be much appreciated
What happens if you let it sit on half choke for 10min to warm up fully and then turn choke off? Its probably something as simple as adjusting air screw. Its the little brass flathead one, the flower/star looking one is the idle. Sounds like the sled needs less air so turn the screws all the way in on all carbs then back out 1/2 turn and post results.
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Old 12-22-2012, 03:54 PM   #3 (permalink)
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The pilot air jet? i have not worked on many carbs so this is new to me. Letting it warm up makes no difference. It idles fine with the choke off just when you rev it up it backfires and revs up really slow
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Old 12-22-2012, 03:59 PM   #4 (permalink)
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The pilot air jet? i have not worked on many carbs so this is new to me. Letting it warm up makes no difference. It idles fine with the choke off just when you rev it up it backfires and revs up really slow
Ok so backfiring can usually be caused by to lean conditions. Take a good pic of the plugs and post them. I will tell you if its running lean or rich.
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Old 12-22-2012, 04:15 PM   #5 (permalink)
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hope these pictures will work
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96 Indy Storm 800-spark1.jpg   96 Indy Storm 800-spark2.jpg   96 Indy Storm 800-spark3.jpg  
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Old 12-22-2012, 04:17 PM   #6 (permalink)
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hope these pictures will work
Its hard for me to see pictures do to quality. White=too lean black=too rich. If you google image it you can find pics of 8 or so different spark plugs that look different and the condition thats going on the spark plug. I might be able to find one for you to compare to yours. Give me a second!
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Old 12-22-2012, 04:24 PM   #7 (permalink)
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http://www.4secondsflat.com/plug_chart.html
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Old 12-22-2012, 04:37 PM   #8 (permalink)
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is this one any better. Mine doesnt really look like any of those just a light black color
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Old 12-22-2012, 04:54 PM   #9 (permalink)
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Listen man, its easy. Start with cleaning the carbs. Then when you go to put the carbs back it, turn up the iddle. You should be MORE than good after you do that.
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Old 12-22-2012, 04:59 PM   #10 (permalink)
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When you are cleaning the carbs, i would expect to see the build up in the iddle jets. Make sure you can see right through them when you put them back it. Based on the pics i'd also through some new spark plugs in.
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Old 12-22-2012, 08:04 PM   #11 (permalink)
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When you are cleaning the carbs, i would expect to see the build up in the iddle jets. Make sure you can see right through them when you put them back it. Based on the pics i'd also through some new spark plugs in.
Take a small piece of wire, twist it and "floss" through the pilot (aka idle) jets. Any spare wire will work just strip it and take just enough to fit in the jet. The plug doesnt really look bad.
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Old 12-22-2012, 08:06 PM   #12 (permalink)
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Take a small piece of wire, twist it and "floss" through the pilot (aka idle) jets. Any spare wire will work just strip it and take just enough to fit in the jet. The plug doesnt really look bad.


I agree that the plugs really don't look that bad. I usually use piano wire for that. Works every time!
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Old 12-22-2012, 08:33 PM   #13 (permalink)
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I agree. A bog off of idle is usually a lean condition in the idle circuit, which is controlled by the pilot jet. The air screw controls the air to the circuit, so turning the screw IN will richen the mix, OUT will lean it at idle. Try turning the screws in 1/8 at a time to see if it gets better. If you bottom the air screw with no changes, the air or fuel circuits to the pilot jet or the pilot jet is clogged. Time to clean the carbs.

I use a single strand of telephone wire (the kind that came with your ancient computer a few years ago) to poke around the carbs. Piano wire is very stiff and can scratch the soft brass and aluminum. Scratches in the small openings could be bad.
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Old 12-22-2012, 08:50 PM   #14 (permalink)
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I agree. A bog off of idle is usually a lean condition in the idle circuit, which is controlled by the pilot jet. The air screw controls the air to the circuit, so turning the screw IN will richen the mix, OUT will lean it at idle. Try turning the screws in 1/8 at a time to see if it gets better. If you bottom the air screw with no changes, the air or fuel circuits to the pilot jet or the pilot jet is clogged. Time to clean the carbs.

I use a single strand of telephone wire (the kind that came with your ancient computer a few years ago) to poke around the carbs. Piano wire is very stiff and can scratch the soft brass and aluminum. Scratches in the small openings could be bad.


I wouldn't even touch the air screw. What you have here is a sled that sat too long and clogged up the pilot jet. If you decide not to clean the carburetors what you will end up with is a engine that will run to lean. What some people fail to realize, is that the pilot jet is working even at full throttle. This means that when you are running the sled, with the choke on, you will be running very lean. (Wich will destroy your engine.

Just do yourself a favor, and remove the carburetors. You will catch on after the first time you do it. just take a lot of pictures with your phone and put back together the way it was before. All you have to do is go to Pep Boys, or even the nearest wallmart, and by some choke/carb cleaner. (I use gumout)

When you take it all apart, put the main and pilot jet in a GLASS cup, fill it with the carb cleaner and let it soak. If you cant see through ALL of your jets after you have done that and blown them clean with an air compressor, use piano wire or even computer wire like he was saying to "un clog" your jets. Do this correctly and your sled should be good as new!! As you'll find out, those old mikuni carbs are pretty simple. Good luck!
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Old 12-22-2012, 08:58 PM   #15 (permalink)
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I wouldn't even touch the air screw. What you have here is a sled that sat too long and clogged up the pilot jet. If you decide not to clean the carburetors what you will end up with is a engine that will run to lean. What some people fail to realize, is that the pilot jet is working even at full throttle. This means that when you are running the sled, with the choke on, you will be running very lean. (Wich will destroy your engine.

Just do yourself a favor, and remove the carburetors. You will catch on after the first time you do it. just take a lot of pictures with your phone and put back together the way it was before. All you have to do is go to Pep Boys, or even the nearest wallmart, and by some choke/carb cleaner. (I use gumout)

When you take it all apart, put the main and pilot jet in a GLASS cup, fill it with the carb cleaner and let it soak. If you cant see through ALL of your jets after you have done that and blown them clean with an air compressor, use piano wire or even computer wire like he was saying to "un clog" your jets. Do this correctly and your sled should be good as new!! As you'll find out, those old mikuni carbs are pretty simple. Good luck!
I dont even soak the jets. Just flos with wire and spray out.
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Old 12-22-2012, 11:21 PM   #16 (permalink)
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I dont even soak the jets. Just flos with wire and spray out.

Whatever gets the job done. Either way, you are going to have to clean the carbs though.
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Old 12-23-2012, 01:36 AM   #17 (permalink)
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Running with the choke on will enrich the air/fuel and make temperatures in the cylinder and exhaust cooler, not hotter.

Fox is right, Mikunis are pretty simple and you should not be intimidated by taking them apart. The jets have to be pretty spotless to work properly, as do the air and fuel passages to the imulsion chamber in the carb. Cleaning should be an annual ritual for anyone that has carbed sleds. And with a triple, you get one extra to play with
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Old 12-23-2012, 10:01 AM   #18 (permalink)
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Ya, its DEFINITELY an annual event like dan said. Haha. I used to have an XLT, those carbs would NEVER stay clean.

By the way dan, your oil intake is based off of how much fuel you have going into the carb (without the choke on) it doesn't matter if you put MORE gas in, because MORE gas doesn't cool your engine. Its oil that cools, and if you aren't getting gas from your pilot jet, you are dumping more fuel in and still no oil, except the oil from the main jet you are still getting of course. So, what you end up with, is an engine that is running leaner. Gas doesn't cool, only oil cools. Choke dumps more gas into the carb (without oil)
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Old 12-23-2012, 11:21 AM   #19 (permalink)
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Oil doesn't burn well, if at all, in the combustion process. Adding oil to the air/fuel mix actually LEANS out the air/fuel ratio because the oil displaces the same amount of gasoline in the air/fuel mix. The lean condition is mostly negligible, but it's still there.

Jetting charts show that rich mixtures burn cooler, lean mixtures burn hotter. Adding the enriching circuit fuel by flipping the choke on to an otherwise properly jetted engine drops the combustion temps quickly (and very visibly if you have an EGT gauge.) I used to run a set of twin pipes on an RMK 700 and I had an EGT gauge on it. Jetted for 7000 feet and running hard at 5000 feet would bring the temps up to almost 1400 degrees, which is close to melt-down. Flipping the choke on would instantly bring temps down to a more reasonable 1200, even at full throttle.

Injected oil intake is based on oil pump RPM and velocity of air through the carbs, not on the amount of fuel delivered. We jet to keep exhaust temps below the melting point of aluminum to keep the engine safe. It's the fuel that is cooling, as the richer mixture burns cooler. Understanding piston wash shows the greater the amount of raw fuel that enters the combustion chamber, the greater the wash and the cooler the temps. I agree that adding the choke to the mix can make the oil/gas ratio greater and if used for extended purposes, could cause issues, but those would be because of under-lubrication and not because of heat. Unless your oil pump mixes the gas at the fuel pump, which adds a whole different set of issues!

Four stroke dyno testing will show the same temperature result in the absence of any oil in the gas. Lean air/fuel burns hotter than rich air/fuel.
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