I have a little 1 liter tube frame runabout. It has always had a bit of hesitation when you mash the throttle at under 3000 rpm . I threw my AFR on it yesterday and saw 22.8 when it hesitated. Except
For that hesitation the AFR looks
Good under all driving conditions.
This told me it wasn’t a lean spot but a misfire. I checked the jets and overall operation and this confirmed the carb was setup correctly, except for idle
Mixture Springs that were too long and preventing me From screwing the idle mixture screws onto their seats. Bottoming the springs yielded just about the right idle mixture.
There are two ways to fix that misfire, lean out the accel pump jet and/or increase timing advance.
So, here is the reason for my post. I bumped my timing ahead by 6 degrees and the hesitation is gone, with no change to the carb adjustments.
Yes, I will probably get some pinging in hotter weather so I will modify the distributor to reduce total advance out.
This confirms (for a second time) that Steve’s advice about having more early advance with Weber’s that run a bit rich. It’s another good reason to get a 123 tune distributor.
John
For that hesitation the AFR looks
Good under all driving conditions.
This told me it wasn’t a lean spot but a misfire. I checked the jets and overall operation and this confirmed the carb was setup correctly, except for idle
Mixture Springs that were too long and preventing me From screwing the idle mixture screws onto their seats. Bottoming the springs yielded just about the right idle mixture.
There are two ways to fix that misfire, lean out the accel pump jet and/or increase timing advance.
So, here is the reason for my post. I bumped my timing ahead by 6 degrees and the hesitation is gone, with no change to the carb adjustments.
Yes, I will probably get some pinging in hotter weather so I will modify the distributor to reduce total advance out.
This confirms (for a second time) that Steve’s advice about having more early advance with Weber’s that run a bit rich. It’s another good reason to get a 123 tune distributor.
John