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joseph

1990 Suzuki LT 4wd need help running issue

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my atv will start right up will idle fine soon as i try to throttle up engine dies,i have changed gas,new fuel pump and lines great compression 188 lbs.new coil new spark plug adjusted valves dont know what to do also rebuilt carb,any help wanted

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Possible air leak. Improper air filter/ dirty. Air fuel screw at wrong setting.
What's the year make and model

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its a 1990 suzuki lt4wd ,i have tried every thing when it first started it ran like a 4cyl. would when only 1 cyl was fireing then it would clear up when i worked the throttle now it just only will run at a idle runs smooth at idle

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It really sounds like a fuel issue.  Have you checked the fuel tank for any blockage ? Maybe dirty filter if there’s one in place as well as a clogged fuel valve at the bottom of the tank.  Also could be dirty carburetor problems.   I would start from the ya k down to the carb and go from there.  

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Something was possibly missed. I’ve done it plenty of times. I’ve rebuilt my carb and put it all back together just to find something that was over looked.  It happens. Secondary looks do usually turn up the culprit  and if not then at the very least it completely rules out that portion of the problem. 

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thanks for advice but i have checked fuel flow even hooked up another tank so it would feed carb by gravity,also i bought a after market carb it does same thing iam not driving the atv its just sitting there in neutarl is there any thing electrical that could cause this? i sure appreceate the help i tried going to the suzuki forum site but after joining couldnt figure out how to ask a question cant even log in anymore its crazy how complicated that site is so i hope you guys can help me i have cleaned tank new fuel shut off new fuel lines new vacume line to fuel pump new coil new spark plug new plug wire new coil rebuilt carb set float

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E brake switch off? My kfx and my banshee have a rev limiter when it's on.

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Your spark may be breaking down as the RPM’S come up.  This happened with my Polaris which had a rev limiter on it also.  

So @06kfx440 may have a point.

I was pointed in the direction of a faulty rev limiter on one of my bikes through the forum here. 

I purchased this spark tester and put it in line with the spark plug. Started and watched the spark break down/fail as I reved the bike.  I removed the rev limiter and my problem was solved.   Worth a shot and cheap enough to try. It’s also a good tool to have.  

Having ruled out the fuel system it may be time to start looking in the ignition system.  

Rev limiter

bad pick up coil 

stator coil problem

regulator

cdi box  

4 of the 5 above listed parts can be tested and the repair manual will explain as far as how and what numbers should be shown on the tester during this process. 

I attached  a pic of the spark tester. 

 

F5844F48-ACEF-4CD9-A89D-679349639777.jpeg

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On 11/2/2018 at 3:33 PM, joseph said:

my atv will start right up will idle fine soon as i try to throttle up engine dies,i have changed gas,new fuel pump and lines great compression 188 lbs.new coil new spark plug adjusted valves dont know what to do also rebuilt carb,any help wanted

Is that the compression reading before or after adjusting valve  just wondering 

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not sitting around a lot compression 188 after valves checked they where actually ok also i had put after market air filter on it because putting carb on and off so much this atv is tough to work on with front and rear fenders on

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was just wandering because this would indicate bad gas or gummed up carb as most others have pointed out its either gas or electrical related

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Check the charging system. Sounds crazy I know but every now and then I get a machine that nobody can seem to fix. An over charge condition from the charging system will cause the CDI to shut down. At idle the machine may be showing 14-15 volts at the battery. As soon as you touch the gas the voltage shoots up (due to higher alternator rpm) and the Ignition system quits. The charging system should charge no more than 14.5v at 2500rpm or so. I usually do this as pre check before I actually start working on a machine. Sounds like you did everything else.

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I can tell you what the problem is Guaranteed!. So please attempt to try my option out . 

Every single Suzuki I have ever owned has done the exact same thing . Suzuki are cold hearted women . PERIOD. 

So what you do is start it with the choke on . Leave the choke on for a while. After about 5 or 10 minutes , the engine will start to Rev and Rev and Rev until it's almost redlining. Then and only then take or turn your choke off . If it's a lever that you pull up , you may have to lightly tap it down a hair at a time . Like tap , revs lower but stays running , tap again , lowers Rev  etc. Until it's off and it stays running and idles with no choke or throttle . Then you can take off , shifting and giving it throttle . If the doing the steps does not allow it to idle on its own , adjust your idle screw so it does. Suzuki carbs are ULTRA ULTRA sensitive with this adjustment , so it may not run with a quarter turn left or right , but it will at an Eighth of a turn . So don't give up , it just takes a while , but once you get that idle screw perfect, Don't ever touch it again EVER. Then you only have to deal with the choke. This is the way all Suzukis are engineered to work . Trust me . Although every post on here has good intentions , I guarantee you success . Good luck my brother.

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thanks i will try that the thing is it never did that before since i bought it i rebuilt the carb at least 5 or 6 times finally bought a different new carb from a place that could get a aftermarket one it ran great for a year and a half  then it would start this i would work the throttle it would straghten out but now it wont . the one thing i noticed was that neddle with the groves is a 1[8 in longer then in a kit ive even tried different kits all have the shorter needle  iam 79 was a heavy equipment mechanic many years figured i could fix about anything but not this ILL TRY WHAT YOU SAID AND THANKS

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Had same issue with my 1994 yamaha big bear 300. Ended up being the vent hose being plugged on carb. Used compressor to blow out lines and runs like a top. I did the whole carb rebuild and clean, spark plug and other things and ended up being a very simple fix. Good luck

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8 hours ago, Kent Mettler said:

Check the charging system. Sounds crazy I know but every now and then I get a machine that nobody can seem to fix. An over charge condition from the charging system will cause the CDI to shut down. At idle the machine may be showing 14-15 volts at the battery. As soon as you touch the gas the voltage shoots up (due to higher alternator rpm) and the Ignition system quits. The charging system should charge no more than 14.5v at 2500rpm or so. I usually do this as pre check before I actually start working on a machine. Sounds like you did everything else.

this is actually very useful thanks for the information! 

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