10 mil gas cub jetting

[JCSO605]

Needing a starting point on jetting my 10 mil cub on race gas. It's drag ported 39pwk carbs 200ft asl 80degrees Thanks

[special06shee]

165m55p was what i was running my 10cub at

[JCSO605]

Thanks.

[JCSO605]

If I'm having to give it throttle to get it cranked what could be the cause? Jetting is 165 main 55 pilot.

[JCSO605]

It will not crank without giving it throttle and kicking it at same time

[RadarRacing]

165 is usually at the bottom end of jet size for 39mm pwks on the bikes I have jetted. I definately wouldnt start there. I would start at around the 175 range and go down if needed. If you have to give it gas to start it then it would either be one of 3 things

1. Needs to have the idle screws set correctly, carb syncing is very helpful.

2. Is lean on the pilot.

3. Is rich on the pilot, airscrew, needle

Usually they will start easy if they are overly rich down low.

You can probably tell if it starts easier if the chokes are needed all the time that it may be a bit lean on the pilot.

[JCSO605]

Ok so if idle is high and starts climbing is that possibly because its lean on the pilot?

[locogato11283]

Sounds way too rich to me. My 10mm Cub with 39PWK consistently ran 158-160 mains and 45-48 pilots. That was at 1,000 feet elevation.

[possum]

160-168 mains I have experienced

[RadarRacing]

Listen to those guys , I have usually seen 35mm pwks in the 145-158 range and 39s in the upper 160s,low 170s but we use CEL needles which are leaner than some and use different builders domes , higher ign timing etc. Thats all a factor in jetting.