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Runs rough until 4100 rom

21 May 2020 17:15
BDub
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Runs rough until 4100 rom #1
I have a ‘69 DT1-250 that runs rough until I hit right at 4100 rpm, 5th gear right at 45 mph. When I get there it immediately smooths out and takes off. I can’t quite tell if it is throttle position or the rpm range. A small opening or closing of the throttle right at that point is an immediate change between smooth and rough. I’ve gone through the carb a couple of times but it doesn’t seem to change anything. Any help is greatly appreciated. Thanks!

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21 May 2020 17:20
yamahahaha
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Runs rough until 4100 rom #2
hmmmmm Can you post pictures of your bike????

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21 May 2020 18:01
Swoop56
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Runs rough until 4100 rom #3
That sounds like roughly the transition point where the main jet is coming into play .
Check your needle and needle jet for numbers to confirm they are still the original parts .
The needle may have been changed out with a carb kit needle , or the needle and the needle jet
may be worn , richening the mid range mixture .

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21 May 2020 18:05
RacerClam
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Runs rough until 4100 rom #4
Its important to know throttle position to identify where the problem is . Most likely needle clip position will change it

Rich

racerclam
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21 May 2020 18:51
BDub
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Runs rough until 4100 rom #5

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