Bike bucking

[graggy]

My 66/80 bbr bike has been running pretty good. One issue I am having is when I first start riding it seems to run nice and smooth for about the first 5 miles or so then when I try to just cruise at one speed about 18-20 mph just giving it enough throttle to stay at that speed it starts bucking. If I give it a little more throttle so it’s pulling harder it goes away until I let off the throttle some and just try to stay at the same speed and it starts bucking again. The chain is adjusted good so it’s not slop in that. When it does start bucking and I pull in the clutch lever it stops bucking. Any ideas on what I should do? If I put it away and ride it the next day the same thing happens. Runs smooth for about 5 miles and then starts doing the same thing again

 

[ImpulseRocket]

Sounds like you are getting a bunch of hesitation or 4 stroking at part throttle. Clearing up by opening the throttle suggests it may be running a bit rich. Have you adjusted the needle at all?

 

[graggy]

Sounds like you are getting a bunch of hesitation or 4 stroking at part throttle. Clearing up by opening the throttle suggests it may be running a bit rich. Have you adjusted the needle at all?

No I have the clip in the center slot on the needle. That’s where I’ve had it since I put this bike together. If I raise the clip up a notch that would make it run leaner right? I guess I could look at my spark plug also. That would tell me if it’s too rich also right?

 

[GW's Motorized]

I had this problem but not too bad with my bike around 25. I tuned the carb and it runs perfect theough the rpm range now

 

[graggy]

I had this problem but not too bad with my bike around 25. I tuned the carb and it runs perfect theough the rpm range now

How did you tune the carb? by changing the clip on the needle?

 

[GW's Motorized]

How did you tune the carb? by changing the clip on the needle?

Yeah, that's all mine needed. I'm at 2000 ft and I had mine one notch lean with the stock air filter. When I changed it to a high flow I had to set it back to the center notch

 

[robe]

Mine was working great at warmer temps with the stock main jet and the needle one notch up, a bit rich at wot.
Now that it is much colder, it is too rich at wot, so I should go to a smaller main and probably have to move the needle back to the middle.

The pouring rains are back so I doubt I'll be riding much anymore for a few months.

 

[graggy]

So I just moved my clip up one notch and went for a ride it’s still bucking. Then I got home and took my spark plug out and this is what it looked like. Should I try leaving the clip where it is now and put a new plug in it?

 

[DAMIEN1307]

So I just moved my clip up one notch and went for a ride it’s still bucking. Then I got home and took my spark plug out and this is what it looked like. Should I try leaving the clip where it is now and put a new plug in it?

YEP...lol...And make sure you gap it to .025 thousandths...NGK-BR6HS

 

[graggy]

YEP...lol...And make sure you gap it to .025 thousandths...NGK-BR6HS

Going to get a couple plugs right now. Thanks!