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55 MPH + Hesitation/Misfire/Stutter

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Yesterday I encountered a stutter in 4th and 5th gear under constant throttle at speeds above 50mph. It is a 2008 drz400sm, has 8000 miles and has the full yoshi exhaust, 3x3, and was properly jetted. It was running perfectly last week. The misfire/stutter is still present under full throttle acceleration once it starts happening while cruising. I have not encountered it under 45mph. Ignition/Stator issue? Help?

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Yesterday I encountered a stutter in 4th and 5th gear under constant throttle at speeds above 50mph. It is a 2008 drz400sm, has 8000 miles and has the full yoshi exhaust, 3x3, and was properly jetted. It was running perfectly last week. The misfire/stutter is still present under full throttle acceleration once it starts happening while cruising. I have not encountered it under 45mph. Ignition/Stator issue? Help?

 

What do you call properly jetted?...Listing your settings may show us what's going on...

A stutter indicates richness and high rpm misfire indicates leanness...

Is the issue better or worse with the air box door removed..?

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As in when I rode friday, everything was still going great. Nothing had been changed for a whole season and the past two months. If i remember right it has a 155 main jet and 45 pilot jet. I have to ride it again to check the airbox as it was late and I needed to get to sleep for work.

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What do you call properly jetted?...Listing your settings may show us what's going on...

A stutter indicates richness and high rpm misfire indicates leanness...

Is the issue better or worse with the air box door removed..?

*25 not 45

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What do you call properly jetted?...Listing your settings may show us what's going on...

A stutter indicates richness and high rpm misfire indicates leanness...

Is the issue better or worse with the air box door removed..?

Took it out for a ride with and without the airbox cover and the two rides were identical in that they both had the stutter issue the same exact way.

So I drained the fuel system, no issues at all there. Double checked the plug, gap was perfect and was not black. Carb was great. Shiny clean. I found the breather on top of the air tube between the filter and the carb was half out of the rubber. I had to disconnect some of the harness to get it plugged back in. Put everything back together and took it for a 20 minute ride and now no issue??

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Took it out for a ride with and without the airbox cover and the two rides were identical in that they both had the stutter issue the same exact way.

So I drained the fuel system, no issues at all there. Double checked the plug, gap was perfect and was not black. Carb was great. Shiny clean. I found the breather on top of the air tube between the filter and the carb was half out of the rubber. I had to disconnect some of the harness to get it plugged back in. Put everything back together and took it for a 20 minute ride and now no issue??

 

you solved the lean condition :-)

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i had these symptoms last fall, and i just replaced the motor, and all was better

 

it would only do it warmed up,, and only do it after i got a minimum of 10miles or 15minutes of riding..guaranteed sputtering,misfireing,cutting out..ONLY above 55mph

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i had these symptoms last fall, and i just replaced the motor, and all was better

it would only do it warmed up,, and only do it after i got a minimum of 10miles or 15minutes of riding..guaranteed sputtering,misfireing,cutting out..ONLY above 55mph

Everytime? Did you figure out what the problem is?

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Everytime? Did you figure out what the problem is?

 

everytime evreyday, for 2 weeks, it had 50,000 miles though so i was expecting the motor condition to deterierate soon..

im glad with my decision because it didnt gredade, and im rebuilding it now ..

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Everytime? Did you figure out what the problem is?

 

everytime evreyday, for 2 weeks, it had 50,000 miles though so i was expecting the motor condition to deterierate soon..never found problem.

got whole bunch of used parts, and new p/rings slapped a new/used motor in and its at 6000miles now

im glad with my decision because it didnt gredade, and im rebuilding the original motor now ..

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Everytime? Did you figure out what the problem is?

 

everytime evreyday, for 2 weeks, it had 50,000 miles though so i was expecting the motor condition to deterierate soon..never found problem.

got whole bunch of used parts, and new p/rings slapped a new/used motor in and its at 6000miles now

im glad with my decision because it didnt gredade, and im rebuilding the original motor now ..

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