KLX351 keeps fouling plugs
#11
05-14-2018 | 09:34 PM
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When you had the carb off and the accelerator pump fixed, did you try running a fuel line/supply into the carb to see if the accel pump nozzle is spraying in the right direction and for the proper amount of rod stroke? This observation would tell you if the pump is operating correctly and your fix was complete. Do you have some good Mikuni instructions for setting the accel pump on that carb? I have the 36mm pumper, but there are some minor differences.
Are you sure your choke rod/shaft is completely closing? There is a rubber o-ring on the choke piston that seals that circuit when the choke is off/in. Sometimes that seal gets worn or defective. You sound sure that this is a fuel richness problem instead of oil, and it sounds like your assessment is correct. On that Muzzy exhaust, that shouldn't be an issue. I have one on mine, and it's a good, solid, functioning aftermarket exhaust.
Are you sure your choke rod/shaft is completely closing? There is a rubber o-ring on the choke piston that seals that circuit when the choke is off/in. Sometimes that seal gets worn or defective. You sound sure that this is a fuel richness problem instead of oil, and it sounds like your assessment is correct. On that Muzzy exhaust, that shouldn't be an issue. I have one on mine, and it's a good, solid, functioning aftermarket exhaust.
Not sure what o-ring you're talking about. Totally possible it's not there, i'll have to double check my parts. If i'm seeing correctly on the exploded diagram its part number 65 (https://www.jetsrus.com/individual_p...07_160_su.html). Does it seat on the piston itself (like around the needly part of the piston) or around the threading against the throttle body?
#12
05-14-2018 | 09:39 PM
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One way to see if it’s jetted rich is remove the air box lid completely. That way it will get the maximum air it possibly can. If it runs better you know the answer. You might need to go one jet size leaner. I would run the lid in wet conditions like water crossings but in so cal there’s not a lot of that.
Also before doing anything try turning in the fuel mixture screw 1/2 turn to lean out the gas n air mixture. Try 2 turns out then 1 1/2 to see how your engine reacts. Let us know how it goes
Also before doing anything try turning in the fuel mixture screw 1/2 turn to lean out the gas n air mixture. Try 2 turns out then 1 1/2 to see how your engine reacts. Let us know how it goes
Turns out I messed up the fuel mixture screw -- originally thought it was a drain screw and played with it til i realized what i was doing. So the original screw setting is wrong. I tried resetting that mixture screw by: letting the bike warm up at idle, starting at 2 turns out from fully screwed in i backed the screw out still it started coughing and then turned it 1 half turn in. Reset throttle idle to a lower idle, did the same thing.
#13
05-20-2018 | 07:39 PM
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i replaced the needle, got new main/pilot jets at the same size (140/40) just to be sure, cleaned the carb again, checked the choke piston. reassembled everything, went on a 90mi ride, fouled plug again... im going crazy
should i go leaner jets, or should i move the needle clip first?
if i want to do the airbox test -- should i go on a real ride without the airbox lid? my house is at ~100ft and most of my riding goes up to 2000-3000ft... or would i be able to tell just running the bike at my house without the lid? i dont really have a good ear for moto engines yet but if i know what to listen for and its fairly obvious....
should i go leaner jets, or should i move the needle clip first?
if i want to do the airbox test -- should i go on a real ride without the airbox lid? my house is at ~100ft and most of my riding goes up to 2000-3000ft... or would i be able to tell just running the bike at my house without the lid? i dont really have a good ear for moto engines yet but if i know what to listen for and its fairly obvious....
#14
05-20-2018 | 08:05 PM
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Posts: 1,360
From: So Cal
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The stock pilot jet is a 35. Unless your at sea level and it’s a warmer climate like so cal I don’t think a 40 pilot is the right jet, a 38 is a better choice. I ran a 40 pilot but the fuel mixture screw was at like 1 1/8 turns out on the big bore klx.
Your over jetted on the pilot try the 38.
Taking the airbox lid off will help your carb/engine run a little leaner and provide you with better results, but the real fix is the right jet
Your over jetted on the pilot try the 38.
Taking the airbox lid off will help your carb/engine run a little leaner and provide you with better results, but the real fix is the right jet
Last edited by RaceGass; 05-20-2018 at 08:10 PM.
#16
05-20-2018 | 08:12 PM
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Joined: Jun 2008
Posts: 1,360
From: So Cal
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I know this sucks but you should only do one adjustment at a time. That way you can determine if what you did worked. If you do two things at once you might find mixed results. It’s best to do one thing at a time. You’ll find suggestions like this in other sites
#18
05-20-2018 | 08:16 PM
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From: So Cal
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Usually I found that deceleration popping can be adjusted out with the fuel
mixture screw turning it out till
the problem is corrected. But after going 3+ turns out you risk losing the screw. That’s why I increased my pilot jet
mixture screw turning it out till
the problem is corrected. But after going 3+ turns out you risk losing the screw. That’s why I increased my pilot jet
#20
05-20-2018 | 09:05 PM
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One more question: is it possible my exhaust/muffler is clogged up with soot causing air starving?
The previous owner lives at same elevation, rides similar places, never messed with jetting after tuning, and said he's never fouled a plug in 10 years on that bike. so i'm a little hesitant to mess with the tuning until im sure its nothign else
The previous owner lives at same elevation, rides similar places, never messed with jetting after tuning, and said he's never fouled a plug in 10 years on that bike. so i'm a little hesitant to mess with the tuning until im sure its nothign else
Last edited by ldkr; 05-20-2018 at 09:12 PM.