Engine bogging in rpm range at wide open

1

1972k1Candyyellow

New Member
Hi mates, i installed a yx140 on my ct70 and im in the tuning process of the carburetor . The carburetor is a Nibbi pe26 and it idle well for an extended period of time and the engine got a lot of power at top end. I have a problem when i’m cruising around (1/4 throttle to 1/2) and i suddenly twist the throttle , the engine is bogging (like a rev limiter) a bit (2-6 sec) before it revs out and make full power. I have tried several main jets and i have the same result if i use a bigger jet (118) or a smaller jet (110). If im progressive when i open the throttle i don’t have this problem. Also when im on neutral at idle and i suddenly twist the throttle the engine want to stall , i have tried a smaller pilot jet and it is worse so i will have to buy a bigger pilot jet i think. But i really dont have a lot of idea about my problem when im cruising and the bike is lagging when i twist throttle. Could it be a fuel line/starvation issue or a carb float issue or maybe a cdi timming issue ( i have a chinese 5 pin cdi from amazon without rev limiter) or is it related to the fact that i don’t have the right pilot jet?

thank you
 
Old Guy Too Many Bikes

Old Guy Too Many Bikes

Well-Known Member
I think you should try a larger idle jet. Since you have a smaller one that doesn't help, why not ream that one til it's slightly larger than stock. Also, have you tried playing with your needle position. Costs nothing and it will either make it better, worse, or stay the same.
 
1

1972k1Candyyellow

New Member
Thank you for your advice i appreciate. I tried to play with but i did not get a significant improvement with that. I will try a bigger pilot jet when i receive the jet kit this week.
 
1

1972k1Candyyellow

New Member
Hello guys , i tried a lot of main jet and pilot jet combination and always the same results. The engine is pretty new and i remember that with the carburetor straight out of the box it was not making bugging like that, i was using a shorter gearing and now i have a longer gearing but nothing really crazy so now i really think that it is a electrical problem since it was not always bogging like that. Im thinking about the CDI of maybe the stator . Does some guys have experience in these parts issue? As i mentionned i always have the problem at certain rpm when a accelerate or when i play with throttle in neutral.
 
H

Honda Hornet

Member
Both of the two small Hondas I have have a spot on the RPM that is a little less strong. This might just be the nature of single cylinder motor, but I found adjusting the needle position (for me it was allowing it to go in one notch lower, because I was rich) it got much less. I meant to go back and try moving it another notch lower, but never did. Pretty happy with it, even if every once in a while I notice that I am cruising at just below the weak RPM spot, so when I try and kick it up, it glurgs (technical term) for a moment before picking up.
 
1

1972k1Candyyellow

New Member
Honda Hornet said:
Both of the two small Hondas I have have a spot on the RPM that is a little less strong. This might just be the nature of single cylinder motor, but I found adjusting the needle position (for me it was allowing it to go in one notch lower, because I was rich) it got much less. I meant to go back and try moving it another notch lower, but never did. Pretty happy with it, even if every once in a while I notice that I am cruising at just below the weak RPM spot, so when I try and kick it up, it glurgs (technical term) for a moment before picking up.
Click to expand...
In my case my engine is a yx140 semi auto and my carb is a 26mm pe26 Nibbi. I will try change to needle position before changing the cdi, but in my definition of the needle position , i see a difference mostly when in cruising or slightly accelerating
 
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