wack wack wack at low speed

[skizman]

My YD100 is still breaking in, but at real slow speed the engine does a wack wack every time the piston goes up and down. If I start giving it throttle, the wack starts going away. It moves ahead pretty good but has little misses and sound of engine keeps changing, plus it won't go to WOT. I keep playing around with the needle setting and jet. Needle is set at 2nd notch from top....jet is 60 (I'll try a 70 next)...B6HS plug set at 25....and NT carb.
Your expertise is appreciated!!

 

[Greg58]

You may be trying to ride it too slow, try raising the idle rpm slightly and see if that helps. What kind of speed are you reaching? If you’re getting in the upper 20’s I would wait till it’s broken in and adjust then, often the power and performance get a lot better.

 

[skizman]

I know the speed gets up in the 30s. I keep speeding up and slowing down to help it break in. But raising the idle will only let it idle higher at idle but won't have any effect while running at a lower speed....right? Today I'll gap the plug to 30 and go up on the main jet to 70 to see what happens.
thanks

 

[Greg58]

The needle controls the mixture till about 3/4 throttle then it’s the main jet. Lowering the clip on the needle makes the mixture richer, raising makes it leaner. I like to tune backwards, I get the main jet size right first then adjust the needle for low end.

 

[Greg58]

26-28 with a NGK B6HS has worked well with all of mine, I have run the BP6HS in some , on one engine the piston closed the gap so the standard tip is recommended.

 

[skizman]

Ok thank you!!!

 

[Venice Motor Bikes]

These engine kits are geared to cruise at higher RPMs... you'll feel a 'chug-chug-chug' in the engine if you ride too slow.

Don't mess with the carb until the engine is fully broken in.... it'll start to run better the more it breaks in.

To break it in, I use 32:1 oil mix & ride it like you stole it.

 

[skizman]

These engine kits are geared to cruise at higher RPMs... you'll feel a 'chug-chug-chug' in the engine if you ride too slow.

Don't mess with the carb until the engine is fully broken in.... it'll start to run better the more it breaks in.

To break it in, I use 32:1 oil mix & ride it like you stole it.