Originally Posted by jmarksdragster
At 4000 RPM are the secondaries even open? I would still plug the secondary PV and jet up. Put an 8.5 PV in the primary, if it still appears flat try a 9.5. It needs to open when the load is high enough to warrant the extra fuel. And don't worry about any effect on idle, the idle jet is much smaller than the main jets feeding them. As far as the sputtering at 1600, have someone hold it there and cover one of the idle air bleeds, if it gets better try covering two. That would tell you the IAB/IJ sizes are too lean for the transition circuit and need to be changed to enrich the circuit. If it gets worse, then it is too rich. As far as the idle, pull the carb now that the idle speed is set and see how much of the transition slot is showing. should have roughly .020 exposed with the blade set for the correct idle speed. What kind of timing curve do you have? Insufficient initial timing will make tuning harder and will run poor, with that much cam I would expect a minimum of 20˚ initial, and maybe up to 25˚
Hi Mark, so glad you're still here...and your feedback is greatly appreciated.
Just wish I was further along with this 850 vs where I'm at > not much boating time and with the season coming to a quick end, I may only be out 2-3 times more.
At 4000 I would think I'm into the secondaries > at least some, but don't know for sure.
Question > if the carb is into the secondaries, what would be the reason to go higher w/PV on the primary side? Unless you're thinking the secondaries are still closed? My concern would be overly rich at cruising rpm's 3-4000
I can certainly block the secondary PV but let me ask you this > (if) the 6.5 isn't opening until some 4800 RPM why not just leave it and still raise the secondary jets to maybe 86?
I will pull the carb tomorrow to have a look at the transition slot.
Timing > I'm running a MSD RTR dizy > if memory serves me I'm a little conservative on total timing > 32* with 12-14 initial > all in @ 3000 rpm.
I can take it to 35* total but would need to change out the advance springs for your suggested 20* initial > just hope it doesn't bump against the starter when starting hot.
I went a little conservative on total timing for fear of detonation.
Question > conservative timing would lead to higher vacuum readings, correct?
Again, thanks for your time and feedback, Ray