9801srx
Member
hi, planing on putting machz 38's on my 780 soon and need to decide what needle and nozzle combo will be safest for my application.the engine has a race ported case ,mr viper cyl's,13.8:1 comp 7.1 corrected and big bore pipes. sled is used for trail riding also so lots of time spent on the needles. the three needle and nozzle combo's i have are 8aby1-40 with o-3 nozzle,8ady1-41with o-2 and 8agy1-xx with o-4. would one of these stock combo's work good or a certain needle with a certain nozzle be better.mr.viper,valin or others who have experence with this ? thanks neil.
valin
Active member
run the 8ady1-41 needles, and the o-4 nozzles.
13.8:1 CR? What fuel are you running with that? Out of curiosity, what is your cranking compression with that CR on those cylinders?
13.8:1 CR? What fuel are you running with that? Out of curiosity, what is your cranking compression with that CR on those cylinders?
9801srx
Member
thanks. 97 octane give or take.70%91-30%112. compression is low 150's. i got the nozzle rating figured out o-2 leaner o-4 richer but the needles not so sure.the way i got it figured is that all 3 have the same 1/4-1/2 fuel flow and the same full throttle flow but the rate at which it richens from 1/2 to full is different.the8aby1 being the most gradual 8ady1 a bit quicker and the8agy1 being the quickest increase in flow for a given throttle setting,would this be on the right track.