What is with the POP STALL

[blackbetty]

Osteoderm, are you running stock bore? How many turns out on your mix screw are you?

I have attempted to drop the needle to try but it seemed to be too lean in the midrange; I haven't played with raising the needle at all since I'm already on the rich side of things.

I was definitely too fat on the main jet though because it seems to pull cleaner with the smaller main.

On my ride home yesterday my bike died in traffic like 10 times. I was so pissed because on my way to work it ran beautifully and I thought I had it licked. It just ups and quits when it's sitting at idle, doesn't seem to be doing the little soft shot like before, so I will raise the idle speed a bit and keep on tuning. This condition presents itself with even the smallest incremental changes on the carbs.

I played with the timing a little this morning and it seemed to help. I still need to take it on a ride.

 

[osteoderm]

Stock bore, long TC Bros intakes, Gordon Scott 2-1 exhaust, PAMCO, PMA... I expect that my overall fueling requirements would be a little less than your 750, but parallel enough to be worth sharing.

Made a heap of changes today, each followed by a mixture re-set and a test ride. Beforehand, I checked the timing, cam chain tensioner, and valves, and all looked good.

185 main, 27.5 pilot, 6F9/3, mixture 1-3/4 turns out, slide at 5/32" - Smooth off-idle and transition to midrange, but tends to die at stops if not blipped or idle held high. Won't take any choke without dying, but reliably starts with 1-3 kicks and a touch of throttle. Plugs black but not foul.

Same settings, needle dropped one notch - Very slight improvement in warm idle quality. Plugs checked, look a little rich. Timing checked with strobe, looks right on the money both retarded and advanced. Plugs still black but not foul.

I liked where your settings were going, so I headed thataway, raising the main and lowering the pilot... 190 mains, 25 pilots, 6F9/3 (back to middle position), mixture at 3/4 turn out - Idle much improved, can be brought down to 1600-1700. Only time it stalled out was at a stop-sign at the bottom of a steep hill (surging from float through pilots?). BUT... coarse popping on throttle-closed overrun, and an annoying off-idle hesitation. Will stand the choke, but didn't need it, at least when warm. Still starts like a champ.

Same settings, needle raised one notch, mixture 1 turn out - less popping on deceleration, off-idle to midrange transition still a touch hesitant. Had burnt my fingers enough already, so neglected to check plugs.

HOWEVER - in all the above settings, I have a crappy problem at approx 5k rpm; the bike starts missing and bogs. If I roll to WOT from a lower rpm, the carbs bellow and she just goes... until the revs build, then the missing starts. This had me thinking that it could be ignition rather than carbs, but timing checks out okay, and I'm trying not to adjust too many things at once.

Tomorrow I'm going to retard the timing a touch. I have 22.5 pilots to try, along with 195 mains. I'll clean the plugs again and recheck the floats.... anything I'm missing?

For what it's worth, I'll report back what I find out.

 

[osteoderm]

More changes today... Larger mains wasn't fixing anything for me, so I went the other direction, if for no other reason than to find out what would happen.

From yesterday's settings (190 mains, 25 pilots, 6F9/4, mix 3/4 turn out), I changed to 180 mains and retarded the timing a teensy bit. Had to dial the mix back in 1/8-1/4 turn. for idle. Off-idle hesitation gone, no popping on decel, no stalling. No hassle low idle. Throttle seems less responsive, but smooth. Midrange seems to have less oomph, but smooth. Starts good, takes choke (but does not need it). Feels like less power, but overall very docile; everything below 1/2 throttle and/or 4500-5000 RPM is like buttah. Pulls from lugging speeds without complaint (think lazy 2nd-gear roll-through stop-signs, etc).

I am both proud and ashamed to say that I have just tuned an excellent bike for under 40mph city traffic.

Panic's guide suggests mix screws less than 3/4 out means under-size pilot. For me, I'm thus looking at 25 pilots and a raised needle, or 27.5 pilots and a dropped needle.

Still with the %$#^$% missing and shit at high(er) RPM. Got onto some open road today and played around; I'm feeling more sure that the missing is tied to engine speed, not throttle position. This has me thinking ignition, not carbs... Left plug dark but not foul, right plug dark on exhaust side.

Well, the weekend is over, fairing is stripped off, and the bike is out of commission for the rest of the week with other modifications. Going to completely tear down the carbs and re-clean them, quadruple-check my timing marks, etc.

BTW Blackbetty: watched the vids, read the write-up on xs650chopper... your bike is effin' sweet!