Dead spot when hitting the throttle!

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#1
I was a great day for a ride! At last I took my KDX 220 out for the first time. I couldn't help myslelf I went to the nearest location which is a creek bed - pretty muddy. What a blast. Since this is the first time I rode I sure found a dead spot when hitting the gas in first. I've ordered a FMF pipe and hope this takes care of it. Has anyone else ever experienced this dead spot? If so how did you fix it??
 

MN KDXer

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#2
A 220 should not have any dead spots in the lower part of the powerband, IF it is healthy.

I would suggest (not necessarily in this order)-
a) Check the carb for cleanliness, especially in the pilot jet. (even if bike is new)
b) (if the bike is used) Check power valve operation. A quick check up short cut, is to remove the large flat-bladed screw on the left side of the cylinder. Next, use a socket to GENTLY rotate the hex nut. I forget CCW or CW, but it should go fairly easily, and then snap shut with enthusiasm.
c) If the carb is bored, install Boyesen reeds.
d) Adjust the air screw in a 1/4 turn at a time.

Also, if the gas is old, dump it and get some fresh juice.

Hope this helps!

------------------
-01 RM250
-Vet A Enduro and Hare Scramble Rider.

[This message has been edited by MN KDXer (edited 03-20-2001).]
 
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#3
Originally posted by MN KDXer:
A 220 should not have any dead spots in the lower part of the powerband, IF it is healthy.

I would suggest (not necessarily in this order)-
a) Check the carb for cleanliness, especially in the pilot jet. (even if bike is new)
b) (if the bike is used) Check power valve operation. A quick check up short cut, is to remove the large flat-bladed screw on the left side of the cylinder. Next, use a socket to GENTLY rotate the hex nut. I forget CCW or CW, but it should go fairly easily, and then snap shut with enthusiasm.
c) If the carb is bored, install Boyesen reeds.
d) Adjust the air screw in a 1/4 turn at a time.

Also, if the gas is old, dump it and get some fresh juice.

Hope this helps!

Thanks much for the advice! If it's jetted for a higher altitude could it also cause this problem??
 

Canadian Dave

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#4
MNKDXer has covered the bases. I'd add just one more thing :

Could you describe this bog in more detail? When you wick the throttle open does it hesitate before making power or is it more like the bike is miss firing and sputtering? I'm wondering if it could also be a jetting issue?

What jetting are you running and under what conditions?

In stock form the KDX is quite plugged up with a restrictive pipe and air box lid. What you're experiencing could easily be normal. The stock performance could be described as flat depending on what you're comparing it to. Its obviously hard to tell from here without a common reference point to compare it to.

David


------------------
www.justkdx.dirtrider.net
 
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#5
I had a similar problem this past weekend: bike all of the sudden wouldn't pull at slow speed. As soon as it would build some revs, it ran great again.

Turned out that the air screw was loose and had backed itself out about 3 turns too far.

My buddy fixed it by turning in the air screw while gapping the throttle until all hesitation was gone. It made an incredible difference. Bike runs great again. Good luck.
 
- a d v e r t i s e m e n t -

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#6
Originally posted by robertf97:
I had a similar problem this past weekend: bike all of the sudden wouldn't pull at slow speed. As soon as it would build some revs, it ran great again.

Turned out that the air screw was loose and had backed itself out about 3 turns too far.

My buddy fixed it by turning in the air screw while gapping the throttle until all hesitation was gone. It made an incredible difference. Bike runs great again. Good luck.
Thank much for the info! When I turned the throttle in first gear it would hesitate then take off. I'm not sure of the exact jetting but it's for high altitude 6 - 9 thousand feet.
 
- a d v e r t i s e m e n t -

Canadian Dave

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#7
Sounds like it could be a lean pilot circuit which is the same problem robertf was having and point d on MNKDXers list.

I'm guessing its still quite cool there right now and you're air screw needs to be adjusted to compensate. Turning your airscrew in will richen the circuit. Give it a try and see if it fixes the problem.

Check out www.justkdx.dirtrider.net click on tech tips then carb tuning for more details.

David


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www.justkdx.dirtrider.net
 
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#8
I have had this happen before and it turned out to be some grungies in the carb. I was on a day ride and decided to take the carb off at lunch disassemble/clean while I ate lunch.

If you like PB&J you should try it with a little premix on it. mmm mmmm good.

It took care of the problem.

The cleaning, not the PB&J!
 
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#9
Originally posted by GreenMan:
I have had this happen before and it turned out to be some grungies in the carb. I was on a day ride and decided to take the carb off at lunch disassemble/clean while I ate lunch.

If you like PB&J you should try it with a little premix on it. mmm mmmm good.

It took care of the problem.

The cleaning, not the PB&J!
Thanks much to all for the info, though, I'll pass on the premix with my PB&J.