XJ550 Bogs on throttle snap

Hey guys, been a long time.

Long story, but bike started making lotsa chain noise last year. Compression test showed #2 low, but within spec. Leak test.... 50% air leakage from cyl 2. Took it apart and rebuilt it. Piston rings. That part was fixed, but then it started running all schizoid on me. Propane test showed 5 of the 8 shaft seal o-rings were leaking. Replaced em all.

Took it for a ride, and almost didnt make it home. Float valves and seats were toast and she started dumping fuel. None made it into the crankcase, fortunately. New float valves and seats for all. Would up having to adjust float levels because the floats were set super lean... wonder if the valves were slowly on their way out and I just kept on leaning em to keep the float level I want. I'll own that one.

Latest test ride much, much better than it has been in a long time. Starts well, idles, doesn't hang, synced up perfectly. My only issue is that when I snap the throttle from idle, or low power to WOT, it bogs for about a second, and then catches up, without easing off the throttle. Only under load - doesn't do it while in neutral. No bogging if you roll the throttle slowly on, but it is especially noticeable when you add power at the bottom of a hill... bogs, and then takes off.

I lost my colortune in the divorce (another long story), but each idle mixture screw is backed out 2 1/2 turns. Valves clearances perfect, took the carbs to church a month ago and clunking, float level on target.

Ideas? Im thinking vacuum diaphragm springs that are toast (replaced an action spring on an old shotgun, and its basically new again), but I am trying to avoid the confirmation bias simply because I replaced a 70 year old spring and got results once.

Trying not to spend money on it if possible, given that the next layoff with all the present insanity might be me. But definitely wanna get the bike back to her former glory.

Or do I just not know CV carbs that well, and it's normal?

Cheers,
Smack

 

I’d get another Colortune.......we gotta find out if it’s starving for a micro second, or if it’s swamping for a microsecond.

hmmmmm......what happens if you take your air filter out?

 

Cheapest I can find right meow is $175cad. But will keep on looking, as it is definitely the best way to figure that out.

Good call Dave, I'll give that a whirl... we've supposed to get a bunch of rain out here, so next sunny day I'll pull the filter and see what happens. Just went for a quick jaunt down the street and pulled the plugs. Textbook. I might try and make it bog and pull some plugs next.

 

is it worse the last 10 minutes of your ride or the first 10 min

 

Hard to tell. Did it cold, and hot. I'd say worse hot. Maybe.

 

Just had a thought... when I had the colortune (3+ years ago), only way I could get a constant blue flame was with the mixture screw back 1 turn. A mechanic buddy at the time convinced me that was bad, and I should put in pilot jets one size smaller. Wham, colortune at a little over 2 turns. Close enough for me (present me apologizes for idiot me). Stock is #35, I am running #32.5.

I have been thinking - what if the leaking throttle shaft seals and leaky valve seats both started to occur at the same time? Explains why I used to have such a hard time getting the right fuel level - I always just chalked it up to a sticky float.

Sourcing some 35's might be in order.

 

So you went to smaller jets which deliver less fuel rather than larger which give a little more

 

Correct

 

Put the original idle jets back in. Try it.

 

one turn out on mixture screw may indicate a problem.
could be the hole the mixture screw has been made bigger or the o ring is flat and hard.

if it works at 1 turn and plugs look good go with 1 turn

also go to stock pilot jets