I’m breaking in my KA after top end rebuild. I’m gonna drive at full throttle and choke the airbox with my hand to keep revs down, try not to stay at constant rpm. Carb is set at 68 mins high and 68 mins low. Am I gonna foul the plug? Should I go leaner?
I was planning to break in at 68 mins and then lean out to 60 mins…
Did your motor rebuilder run it all? Some do, some charge more for dyno break in. I don’t think you can go too rich. Like 90 min especially on the high circuit. Even though the manual states 20:1, 16:1 is usually the norm. This is what the manual states for new and would work for rebuild too.
The running-in must be made following a few basic rules:
Carburation setting. Start with basic setting on the rich side.
Warm the engine gradually for 5 minutes, driving some laps at low speed, smoothly closing and opening the accelerator (if a tachometer is installed, never exceed 9.000 ÷ 10.000 RPM). Never keep the same RPM for a long time but alternate the speed.
Gradually increase the vehicle speed for about 5 minutes (with ¾ throttle opening). Never keep the same RPM for a long time but to alternate it.
Increase the speed driving some laps, for about 5 minutes (with acceleretor fully opened on circuit twisty parts and enrich the carburation at half straight (cover with the hand the inlet hole on the inlet silencer for an istant, keeping the throttle open).
Thanks. If you say I can go that rich, then 68 should be no problem.
Even though IAME states that setting, I have found some carbs are a little different and need to run a richer setting. In my experience, these carbs are more susceptible to lean bog (losing power when needles are too lean) than rich fouling, especially at race pace speeds.
Ya, I have definitely had lean bog in low speed hairpins. Didn’t experience that today. Motor was tremendous. Thanks again.
your spark plug colours can say a bit of a story also . but better to be rich in break in precidure .. than lean !