I have a stock -77 that does not rev nice between 7500-8500 rpm. Below and over it runs nice. Pilots are 30, main jet 270, 280 and powerjets 215. Primaryclutch 102 with N1 and 208228a spring. Does anyone have an idea what might cause this?
YAMMIEGOD3:16
Active member
WHATS YOUR SECONDARY SET AT. 3:16 (yammie tony)
4 and 120YAMMIEGOD3:16 said:
YAMMIEGOD3:16
Active member
TELL YA MORE I THINK ABOUT THIS THE OLD POWER JET MIGHT BE THE CULPRIT. I WOULD BLOCK IT OFF AND RUN A FIXED MAIN. 3:16 (yammie tony)
opsled
Active member
One problem I have encountered with P-jet carbs is wrong line sizing. The line that goes from the bowl up to the P-jet needs to be properly sized. I have had guys bring them in that had put all new lines on their sled thinking they were doing a good thing but the problem I have seen is that most will use cheap aftermarket line that doesn't fit well. The line that some have used for the P-jet has an ID that is too large. If thats the case then the weight of the fuel in the line is higher and the vacume produced to pull it up isn't enough to overcome that weight as fast as it should (if it will at all). You can get a lag in fuel transfer up the line to the P-jet because of oversized line which will cause the engine to starve and run lean during that period and a slowdown in flow which can keep it lean at WOT.
I had this with one guy that burned down one side on a Vmax 540 engine. He had changed the line on that side because it was bad but left the other alone. With the carbs off the sled and in hand I blew through them one at a time with compressed air. The bowls were full of fuel and the slides were open. The one with the OEM P-jet line pulled fuel up instantly and sprayed out perfectly. The one with the new (oversized ID) line brought fuel up very slow and it just sputtered out the nozzle. I fixed the cylinder, put 2 new OEM lines on the carbs and his problem was solved.
Just a thought, Phil (opsled)
I had this with one guy that burned down one side on a Vmax 540 engine. He had changed the line on that side because it was bad but left the other alone. With the carbs off the sled and in hand I blew through them one at a time with compressed air. The bowls were full of fuel and the slides were open. The one with the OEM P-jet line pulled fuel up instantly and sprayed out perfectly. The one with the new (oversized ID) line brought fuel up very slow and it just sputtered out the nozzle. I fixed the cylinder, put 2 new OEM lines on the carbs and his problem was solved.
Just a thought, Phil (opsled)