when jetting the carb down how many sizes should i go down at one time.should i jet all four corners the same,or leave the back bigger.will the power valves be fine or do i need to go smaller.i do not have a vacum guage,so i do not know where the vacum is.the carb is 950 proform.the plugs where pretty black.
Without knowing about your combination its difficult to make a suggestion.In most cases you run 2 sizes larger jets in the secondaries.
You may have blown powervalves and are sucking too much fuel into the engine and it cant burn it all.
Does your engine blow out black smoke at w.o.t.?If so you could try dropping the jets down 2 sizes and recheck it.Its safer to be a little rich than run it too lean and melt a valve or piston
Recommended to change 2 jet sizes up or down. Check plugs and adjust. You can stagger the jet sizes according to the plug readings. Good info in the gearhead section on reading plugs.
Tech link section in gear heads. Great info.
it does not blow out black smoke.i had a 850 on it for two years and always ran fine.i am going to build a bigger motor over the winter so i bought a bigger carb.the air out here is real hot and dry,just trying to tune it for the weather.
As far as making changes, I'd make 1 or 2 at a time, equally on all 4 corners. The only way to tell on the PV is to bolt the carb on, run it, and see what your highest engine driving vaccumme is, and cut it in half (I believe that is correct) (aproximately half) and tune from there for a seamless, un-noticable transition. Just like on a Vac Secc carb, if you can notice the PV opening point, it is wrong.
I once tried to go without the primary PV (I don't have a secc. PV), and rejet to compensate. I'm sure some folks here have done it with success, but I didn't want to spend all summer swapping shooters, accel pumps, drilling air bleeds, etc, to fix the holes in response I created once I got to the ballperk for correct mixtures.
IMHO, all you are going to find with that 950 is you will burn more gas, but that's just my amateur opinion.
i took out the powervalves and put the plugs in. more consistancy sp? imho. anyways i always go up 2-3 sizes at a time. also i never do the primary and secondary at the same time.
it does not blow out black smoke.i had a 850 on it for two years and always ran fine.i am going to build a bigger motor over the winter so i bought a bigger carb.the air out here is real hot and dry,just trying to tune it for the weather.
IMO, if it ran "good" with the 850 on it...go bk to it & have fun for the summer!...the present motor u have prob can't handle the 950 no matter what u do & why not just save it for the bigger motor! instead of beating ur brains out trying to make it work!...i think u will be way ahead of the ballgame...just my .02 cents
fastrat
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