The dark art of jetting - 397cc stroked

[yamagama]

Hi All,

OK so a long way off her running yet but the yamagama 31k engine is (well once it all goes back together) is:

31k engine - stroked by 4mm so a cc of around 397 (68 mm wiseco blaster pistons)
Stage 3 tune by stan
wicked torque head
v force
gp style pipes, of unknown origin
full zeel

Now as for carbs, I have a set of KR1s Keihn's which see to be favoured but no idea where to start with jetting.

I could of course go for standard 250cc set up, then multiply up 75% or so to compensate for the increased cc, but not sure that is science

So question is - any one out there done a stroked engine with a wild(ish) tune with these carbs, and if so where did you start !

Thanks all - and thanks to everyone that has been brilliant help on this site so far.

PS - I am now broke !

[nikfubar]

No idea about stroked engine but tuned 350 running PWK28s & pod filters 152 mains, 42 pilots, standard needles on middle clip. Maybe start richer than that & work back

[tobster]

IMHO the biggest influence on your jetting will be what air filters you use. I run quite a different filter set up to Nik so my jetting is way different

[yamagama]

Hey all - many thanks for the start point, much appreciated; not sure what filters to run yet, I have space so was going to get as long a run between the carb venturi and the filter to create still air; will take a look at the needles tomorrow and post back. Thanks again all, much appreciated !