Another blooming jetting Q...

[Jung]

Apologies if this has been done to death. Is there a difference in main jet sizes running the Dave F mod vs stock?

I'm just about to start up my little home grown 350 - it has stock high tops, stock needles, y-boot with UNI filter, ported cylinders (exh raised a little and widened to 68% of bore. Transfers and boost raised and widened.) I recut the 250 heads for about 45% squish and a total volume of 22cc, squish is 0.95mm. Pipes are home made by me for about 8500 peak from a Mick Abbey design.

I've got a 32.5 pilot / 230 main in it at the moment, fine for some heat cycles and pootling but reading here, seems like the main might want to be bigger?

I'll probably try the Dave F mod at some point but don't have time to order the jets before a ride next weekend.

Cheers!

[m in sc]

w out porting w otherwise similar setup, mines sitting at 270 mains. 250-260 is sort of average though. the fpps on mine pull to the freaking moon so prob has something to do with it.   

[Jung]

Cheers chap. Got it running and heat cycled today, so will have a crack with jetting after work during the week. Sounds happy.

[Jung]

Yay - gave it a couple of good rips in 2nd and third this evening and it didn't blow up! Wheelies nicely in 2nd now on 15/40 gearing. Feels a bit rich everywhere, bit sputtery on the pilots, better on the needles and takes full gas on the mains, without bogging or sputtering. No sign of detonation, which was a bit of a concern as I'm up near 150psi. Hopefully that means my heads are working well!

I'll do a few more miles tomorrow and give it a proper plug chop. So far so good....