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MXwhit

Can't start my YZF anymore!

7 posts in this topic

I have a '98 YZF that has been a wonderful bike for the last few years. I bought it used from a guy that rode in Nevada at ~4000ft. I put an FMF exhaust system on it and changed the jetting to the recommended settings given by the FMF technician. Everything was working fine until I recently learned that excessive compression braking and backfiring during deccelerating was due to improper needle position. So I removed the carb and looked at my needle clip position. It was in the second position and was supposed to be in position four (standard). So I moved it down to the standard position and tried it out.

I struggled to get the bike started at first but thought nothing of it since I had just removed the carb and the fuel needed to get to the carb. Needless to say, I rode for about two hours and was able to start the bike with the kick starter only one time (and yes, I am an expert in starting this bike... I've learned). The only way I got it started was by bump starting it.

From what I know, the needle setting affects the 1/4 to 3/4 throttle acceleration. This range was acting perfectly.

Could this needle change have caused my starting problem? Or could it be a result of removing the carb and not setting the throttle cables perfectly? Anything? I'm at a loss.

Thanks.

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I noticed that the linkage for the accelerator pump is easily tweaked but if the bike ran good after it finally started you have to look elsewhere. The main reason my bike will refuse to start is if it is flooded. Perhaps the throttle cables are out of rig and giving it a little gas when it shouldn't be. Try loosening up the throttle cables till there is slack in them and see if your throttle pulley on your carb is returning all the way to off position (full counter-clockwise). If this doesn't work, try going back into the carb and try putting it at the 3rd notch and see if this helps remedy the situation. If the bike started good before you changed the needle, go back and undo what you did and that will atleast eliminate a problem you may have inadvertently induced. Keep us posted on what you find.

Pat

99 YZ400

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I agree with PK regarding the throttle cable adjustments and the accel pump.

Something else to think about...With the needle put back into the stock position you may need to lean the fuel screw settings as well as the pilot jet.

I have found over the years of owning the YZ-F's that the pilot screw has a tremendous impact on the ease of starting.

yzernie

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Originally posted by MXwhit:

I have a '98 YZF that has been a wonderful bike for the last few years. I bought it used from a guy that rode in Nevada at ~4000ft. I put an FMF exhaust system on it and changed the jetting to the recommended settings given by the FMF technician. Everything was working fine until I recently learned that excessive compression braking and backfiring during deccelerating was due to improper needle position. So I removed the carb and looked at my needle clip position. It was in the second position and was supposed to be in position four (standard). So I moved it down to the standard position and tried it out.

I struggled to get the bike started at first but thought nothing of it since I had just removed the carb and the fuel needed to get to the carb. Needless to say, I rode for about two hours and was able to start the bike with the kick starter only one time (and yes, I am an expert in starting this bike... I've learned). The only way I got it started was by bump starting it.

From what I know, the needle setting affects the 1/4 to 3/4 throttle acceleration. This range was acting perfectly.

Could this needle change have caused my starting problem? Or could it be a result of removing the carb and not setting the throttle cables perfectly? Anything? I'm at a loss.

Thanks.

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I had trouble starting my bike about a week ago, it wouldnt even start, so i figured it was a big deal, but i was wrong, just change the spark plug for a new one, it works wonders, heheh.

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Are you sure the needle was the stock code??Could it have been replaced with a different one?

Did you check the pilot screw setting? You should have reset it and leaned it out by turning it in. Was the pilot jet stock? If it was richer than stock then you may need to go back to a #45 for your altitude.

You richened it on the needle, but circuits overlap and will need some tweaking to get everything right.

James

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I will take a look into all your suggestions this weekend and let you know my results.

One thing to note is that my throttle cable is very tight. Since I purchased the bike and instantly put on Pro Tapers, the throttle has had no play at all. When I rode an '01 426 I noticed considerable play in the throttle on the bike. Each time I have tried to loosen the cable, the throttle does not snap back closed when releasing it.

Is this normal?

Now whenever I remove the carb, I need to be very careful when resetting the cable so that is operates properly. I'm thinking this could be a source of my problem.

Let me know if you have any ideas. Again, I will do some testing this weekend to try and solve the problem.

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