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Weird splutter issue (over fueling?)

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Hi guys, a buddy of mine recently bought a gas gas ec 250, it was stored for approx 2 years, when he got the bike I cleaned the tank and put fresh fuel in, completely cleaned the carb with carb cleaner and put it all back together, started 2nd kick and ran really nice!

 

When he had it out for it's first ride he was complaining it would splutter/bog at certain places, I left him to it thinking it would go away after a few rides. 

 

I got on the bike myself a few days ago to find out exactly where it was happening, what I discovered was if you get the bike into the powerband it runs really nicely, the power is there with no issues however I found if I am trailing around not hitting the powerband once I rip the throttle back it will splutter a bit and then rip, almost like it's over fueling then it boggs/splutters as it is getting rid of the extra fuel.

 

One thing I am thinking is this was the first time I had properly cleaned out a carb and the float had come out of the carb accidentally when I was cleaning it, I put it back in but I didn't check/adjust it, would a badly adjusted float cause this?

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You wouldn't need to adjust the float after removing it, assuming the float height is within spec in the first place.

When the bike is on the stand, idling in neutral and you whack the throttle open, what happens?

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You wouldn't need to adjust the float after removing it, assuming the float height is within spec in the first place.

When the bike is on the stand, idling in neutral and you whack the throttle open, what happens?

 

Sorry I did not get around to doing that however if the biks is warmed up and you pull the throttle down it will rip and then bog and then hit the powerband and run nicely, same as general riding the powerband seems to run fine but it's getting to the powerband that is the issue.

 

Pilot: 42

Main: 172

Needle: #3

Needle type is "N1EF"

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You wouldn't need to adjust the float after removing it, assuming the float height is within spec in the first place.

When the bike is on the stand, idling in neutral and you whack the throttle open, what happens?

 

Today I WOT it while it was in neutral it does not splutter at all, does this prove it isn't the reeds and is definitely jetting?

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Doesn't necessarily prove anything, but that plus starting second kick means the reeds are probably ok. I like to start with fresh reeds, just because they can have large effects on jetting.

If it still sputters while riding, but passes the "whack the throttle" and "highest idle" tests, then try dropping (leaning) the needle by one clip position. N1EF might be too rich on the straight section for a 250, also.

Whacking the throttle open from the lowest possible idle is used to test the pilot and airscrew setting. You do it repeatedly at different airscrew settings until you get instantaneous response from the engine (while fully warm of course). Another method is to find the highest idle with the airscrew (with idle screw at lowest feasible setting).

Check this out: http://www.thumpertalk.com/topic/347305-is-your-two-stroke-running-rich-read-here/

Pay particular attention to the part with the air screw/pilot jet setup.

Edited by clappedoutkx

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Doesn't necessarily prove anything, but that plus starting second kick means the reeds are probably ok. I like to start with fresh reeds, just because they can have large effects on jetting.

If it still sputters while riding, but passes the "whack the throttle" and "highest idle" tests, then try dropping (leaning) the needle by one clip position. N1EF might be too rich on the straight section for a 250, also.

Whacking the throttle open from the lowest possible idle is used to test the pilot and airscrew setting. You do it repeatedly at different airscrew settings until you get instantaneous response from the engine (while fully warm of course). Another method is to find the highest idle with the airscrew (with idle screw at lowest feasible setting).

Check this out: http://www.thumpertalk.com/topic/347305-is-your-two-stroke-running-rich-read-here/

Pay particular attention to the part with the air screw/pilot jet setup.

 

I have ordered new jets that will arrive tomorrow, is it worth giving them a try before anything else? Can you give me some sort of order of what to go by, I really have no idea. It seems like I have so much to test but I'm not sure the best order to go by.

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What jet sizes did you get? What's your region like? Altitude, temp, humidity. Does your friend have the manual for his bike? It probably has a chart with a solid starting point suggested. Start there. Then read this:

http://users.conwaycorp.net/virtus/page2/speed/jetting.htm

Start by adjusting the airscrew. It will determine if you need a different size pilot jet. Then move on to the main and then the needle.

The airscrew has a useful range of 0-3 turns out from lightly seated. It meters the air going to the pilot jet, thereby fine tuning the pilot circuit. Ride the bike for 30 minutes; get it fully warmed up first, before adjusting the carb. Then, to begin adjusting it, turn it all the way in until it LIGHTLY bottoms out, counting the turns. Write this number down, and then turn it out 1.5 turns. Start the bike again and listen to the idle. Use the IDLE screw to drop the idle really low so you can hear the difference as you adjust the airscrew. Now turn it out to two turns, pause and listen. Now one turn, and listen. You are basically just looking for the highest idle and turning the airscrew back and forth in smaller and smaller increments until you find it. If best idle is achieved with less than half a turn open, stop and install the next size richer pilot. If best idle occurs at more than 2.5 turns open, stop and install the next size leaner pilot.

After changing pilots (if necessary), set the airscrew back to 1.5 and start tuning it again. When you eventually have the airscrew set somewhere between 0.5 and 2.5 turns and its idling its highest while in that range, you know you have found the correct size pilot jet. Write down this airscrew setting.

Now you can fine tune the airscrew with the "whack the throttle" method. With the bike still warm and idling in neutral, whack the throttle open and then let it return closed. Let the idle settle and do it again. You are listening for a slight delay in revving after you open it up. Turn the aircrew an eighth turn either way and repeat. When you find a spot where there is no hesitation, you have found your airscrew setting. Write it down, but I adjust mine slightly every ride.

Just do one thing at a time. Its not as overwhelming as it appears initially. Setting the airscrew and pilot probably takes less time than explaining it.

Next, the mainjet.

Edited by clappedoutkx

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What jet sizes did you get? What's your region like? Altitude, temp, humidity. Does your friend have the manual for his bike? It probably has a chart with a solid starting point suggested. Start there. Then read this:

http://users.conwaycorp.net/virtus/page2/speed/jetting.htm

Start by adjusting the airscrew. It will determine if you need a different size pilot jet. Then move on to the main and then the needle.

The airscrew has a useful range of 0-3 turns out from lightly seated. It meters the air going to the pilot jet, thereby fine tuning the pilot circuit. Ride the bike for 30 minutes; get it fully warmed up first, before adjusting the carb. Then, to begin adjusting it, turn it all the way in until it LIGHTLY bottoms out, counting the turns. Write this number down, and then turn it out 1.5 turns. Start the bike again and listen to the idle. Use the IDLE screw to drop the idle really low so you can hear the difference as you adjust the airscrew. Now turn it out to two turns, pause and listen. Now one turn, and listen. You are basically just looking for the highest idle and turning the airscrew back and forth in smaller and smaller increments until you find it. If best idle is achieved with less than half a turn open, stop and install the next size richer pilot. If best idle occurs at more than 2.5 turns open, stop and install the next size leaner pilot.

After changing pilots (if necessary), set the airscrew back to 1.5 and start tuning it again. When you eventually have the airscrew set somewhere between 0.5 and 2.5 turns and its idling its highest while in that range, you know you have found the correct size pilot jet. Write down this airscrew setting.

Now you can fine tune the airscrew with the "whack the throttle" method. With the bike still warm and idling in neutral, whack the throttle open and then let it return closed. Let the idle settle and do it again. You are listening for a slight delay in revving after you open it up. Turn the aircrew an eighth turn either way and repeat. When you find a spot where there is no hesitation, you have found your airscrew setting. Write it down, but I adjust mine slightly every ride.

Just do one thing at a time. Its not as overwhelming as it appears initially. Setting the airscrew and pilot probably takes less time than explaining it.

Next, the mainjet.

 

Thanks for all of the advice, I originally made the thread as it was a family members bike but I have bought it from him, I can see quite a bit of light through the edges of the reed petals, so I am going to replace them asap. 

 

The bike was standing for 2 years, my family member bought it and we did all the usually stuff. Cleaned the carb completely, jets out of the carb ect. Fresh fuel ran through the bike and it started second kick and still starts very very well (always 1st/2nd kick). The bike is very boggy in low RPM but runs fine through the powerbands when it finally gets into it.

 

Does it sound like reeds are my problem?

 

I am running 172 main and 40 pilot right now, I've purchased a few jets both bigger and smaller ready to give a try after everything else. What else should I look at getting done?

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