Fresh rebuild - no fun running

[ChopperRobb]

hey all, i figured its my turn now, lol.
I just started the motor for the first time after a fresh rebuild. A 1977 rephased, 4th oversize with rebuilt bs38 carbs (27.5 pilot, 135 main, needles leaned one step all as recommended by 5twins as a good starting point) airpods, straight pipes, pamco,....all she will do is start and idle (roughly)...if i try to rev her she sputters and pops and cuts off. cam was adjusted and valves adjusted properly...
Any help would be so appreciated.

 

[timbeck]

I doubt you are running 127 pilots......
tim

 

[ChopperRobb]

Oops...27.5 lol
Oh, and the needles are leaned one step (all this as 5twins recommended as a good place to start for my setup)

 

[westonboege]

Sounds like with oversize, pods, and straight pipes you are going to look at richening rather than leaning out... Try upping the pilot by a size or two. Might even richen that needle too..

 

[gggGary]

What happens with some choke applied?
Likely suspects?
orifice in float bowls blocked
float leaks
float valve leaks
blocked pilots
other air leaks, intake, throttle shafts
choke seals fuggled
diaphragms
advance rod, timing issues.
IMHO It'll never run "great" set up like that but it should run "reasonably well" if everything is right.
Pods on BS38's just won't work well, I've tried a few times, always end up with air boxes back on. But I'm kind of fussy about carburetion and smooth running.

 

[ChopperRobb]

So...the culprit was two things...the pods can not be pushed on all the way down or they block a few small air intake passages on the lip of the carb intakes...the other is the threads on my sync adjustment screw are stripped smooth and wont hold the bench sync.

 

[ChopperRobb]

Now i need to figure out what size screw it is for that. Cant find any info about it...anyone happen to know??? Talking about the screw that is on the shaft for the butterflys that adjusts the right carb to the left.

 

[gggGary]

It's a special, really fine thread but same as the throttle stop screws?

 

[ChopperRobb]

Wonder how i go about getting one??

 

[5twins]

Yamaha doesn't list it as being available anymore, but it's probably just as well. They wanted like $13.50 for the thing, lol. Scrounging is probably your only option. Here's a list of models you can score one from .....

http://www.boats.net/parts/detail/yamaha/Y-256-14922-01-00.html

 

[ChopperRobb]

Gary, you’re a genius! I swapped the main idle screw with the adjuster screw and viola! Worked perfect...she’s-a-runnin!

 

[mrtwowheel]

Good thinking CR. That is a hard thread to find, think I have chased after that thread a few times, only to realize, hey, I've done this before.

Scott

 

[5twins]

Pods may not work as well as the original airbox, but the wrong kind of pods barely work at all. Sounds like you may have those.

 

[ChopperRobb]

The pods are good they have a ribbed section that is supposed to be the part that gets clamped over the carb intake...i had them pushed way farther on than that. Now they’re on fine and it goes vroom vroom
I also had to adjust the (pilot screws??? , cant remember what they’re called at the moment) but i had to back them out another 1 1/4 turn from the base setup of 1 1/2 out from just touching bottom.

 

[5twins]

2 3/4 turns out on the mix screws is an awful lot for the '76-'77 carb set. That may indicate another step higher in pilot jet size is needed (#30). As far as the pods go, what kind do you have? The straight foam UNI kind or the pleated K&N style? The pleated style, even if they are clamped on correctly, just don't work that well on CV carbs. The pleats in the filter surface disrupt the airflow, making it "rough" or turbulent. CV carbs rely on a smooth air flow to properly and smoothly lift the slides. The slides bouncing around instead of lifting smoothly makes tuning more difficult.

 

[ChopperRobb]

I have the uni pods. I’ll try the #30, havent done that yet.

 

[ChopperRobb]

So, can these motors be timed without a timing gun?? I have a 277 pamco and hughs pma...i cant rev the motor anymore (im guessing carb issues), so it’ll have to be static timing or timing at idle. Any help i could use badly. Im starting to get the feeling that no one actually has a running, timed, well adjusted bike with these mods and that i’ve been duped.(Or im dogshit fucking stupid, which is probably the case)
Also both carbs have gas around the float bowl drain screws/overflow nozzle area with the left side being worse and it seems it’s only after i shut the motor down. Carbs were freshly rebuilt less than a month ago and kept wrapped and clean.
Edit: float bowl gas leaks fixed...needed to be tightened a little more.
Tomorrow ill try timing it with a timing gun and we’ll see how it goes.

 

[ChopperRobb]

So another issue is cropping up...putting a timing light on my bike kills the motor. Like it draws more juice than the system can handle and that doesnt seem right to me. Any ideas on what could be the problem???

 

[figure8]

Capacitor or battery?

 

[ChopperRobb]

Battery, ballistic 4 cell rated at 2.3 amp hours and 30.36 watt hours