GT550 center cylinder wet fouling at start up

[barncat]

or at least that's my analysis. i've tuned a number of vintage four strokes with Mikunis but this is my first smoker... thought i'd seek opinions.

a shot of ether in #2 carb gets all three to fire and run well, though bike is not registered yet so road testing has been limited. OEM 28mm (as i recall) Mikunis, pods, Strader 3 into 1 pipe, 102.5 mains in #1 and #3, 100 main in #2, probably stock pilot jets, needles 4th clip i believe, air screws out 1 1/2, points clean and adjusted, good spark all cylinders, #2 carb not overflowing so needle and seat must be ok.

maybe a smaller pilot on #2, lower needle, back out air screw in some combination?

save for a front brake that won't bleed this project is mostly done. designed/machined my way out of the starter clutch problem in the "repair" forum in addition to some other custom work...

[bill in okc]

Your bike looks great. I like the look of the cylinder head without the ram air scoop, and painted black looks good too. I had a similar problem with my left cylinder not starting right away. I am not sure exactly what fixed it but I found a passage blocked by old sediment in the bowl - a well that a brass needle -starter jet- fixed to the main body drops into. The blockage was preventing fuel (or enough fuel) from reaching the starter jet. It helped in my situation after I cleared that passage. I had cleaned the bowls with an ultrasonic cleaner, it is nearly impossible to visually inspect the passage. WD-40 passed through it, but I took a small drill bit and angled it in from the bowl and it broke up a concrete-like mass in there.

Could you tell me what shocks you used?
Thanks Bill

[barncat]

Bill- thanks for the input. i suppose it's possible that #2 cyl is not getting enough fuel- i'd guessed it was getting too much... i thoroughly cleaned every inch of the carbs prior to reassembly but as you point out it's still possible to miss something. guess i'll have to try both approaches and see which works. also still need to fab some sort of top seals for the slide lifter rods. the rubber boots were shot.

this bike is kick-only now, btw. one of the poorest kick lever designs i've ever used. i'm going to mod it to change the shape before too long- and it has a tendency to fold closed at the bottom of the stroke even though i welded the ball detent groove back up. also designed a folding footpeg/brake unit that the kicker would pass. the stock pegs and controls are heavy and clumsy.

shocks are those Ebay RFY Chinese units with 7mm spring wire, available in colors and various clevis/eye setups. they are plenty stiff for solo riding. don't buy the heavier 8mm wire shocks unless you're riding 2-up.

i will probably put the ram air scoop back on. sort of a signature piece and doesn't weigh much. just haven't polished it yet. painting the top end was really the only option with all those damper blocks in the fins...

[tz375]

That's good input from Bill. There are many tiny passages that are not easy to clean. Another possibility is that the slow jets may be worn out from too much poking with wires etc over the decades. It's easier to fit new slow jets and they are cheap as long as you get Mikuni originals.

[barncat]

thanks guys. so that's 2 votes for not enough fuel in the #2 pilot circuit as opposed to too much. will investigate that first.

[barncat]

bike fired nicely on all cylinders after re-cleaning the whole pilot circuit on #2 carb. i didn't find any obvious blockage, surprisingly, but so far so good. so you guys saved me some time by pointing in the right direction. thanks.

while i was in there i may have finally figured out a way to save leaky float needles. it doesn't take much of a surface imperfection to screw one up. carefully chuck it in a drill press and run some 600 grit wet/dry paper against the taper...

will put some more pics up in the Project section when it's finished. getting close. have never ridden a 2 stroke road bike before. i expected it to be quicker than some modded CB500T's and TX500's i've built but it seems similar in terms of acceleration. pulls very well with no dead spots once you spin it up off idle, and the Strader sounds great. will have to decide whether to sell it or keep it- i usually build them for resale. i know Jemcos add 6-8 HP.......

also, if anyone checks back in here- is there any good way to verify injector oil feed when the lines are too opaque to see through? i adjusted the oil pump correctly and bled the screw on top, and it smokes a bit out the pipe when you hold the pump lever full on, which i'd expect to see.

[bill in okc]

I'm glad you have it sorted. I used a dark colored oil, Klotz TC-W3, a dark red and it was easier to see in the lines. I was able to back-light the lines to look for bubbles.

[Suzukidave]

Very nice looking 550 ... were you able to get the front brake to bleed out ?

[barncat]

Bill- thanks for oil tip.

Dave- yes, i discovered a new favorite tool. a Mityvac, or similar brake bleeder that sucks the freaking air out of the line in about 60 seconds, and drops the fluid into a nice little bottle for easy clean up. i wasted a lot of time on that brake prior...

another pic added. bike is not quite done but close.

[bill in okc]

I used a small round dental-type inspection mirror behind/under the lines using a small flashlight. I did find bubbles in the left main line that didn't appear to be moving. I tightened the three screws holding the oil pump down, they were not as tight as I thought they were. That may have been what fixed it the bubbles have been gone a while.