Dominant Carb/Cylinder
- Thread starter cgguy09
- Start date
cgguy09
1971 CB350 K3
Negative-results.
So I really straightened the lines and it didn't seem to change (maybe not straight enough, right?) So Doctor'd up this little guy, drilled a hole in a cup, put the fuel line to it, then filled her up with gas....it's gotta work, right? Nope, same symptoms.
Next, I pulled off the carbs pulled out all the jets and the pilot. Everything was already clean, but I cleaned it anyway. I then switched all the parts, including the floats, float bowls and diaphragms from one carb to the other....Nothing!
I'm guessing its gotta be the valves...I mean, I hope its the valves!
cFogs out
BT
NNNN
So I really straightened the lines and it didn't seem to change (maybe not straight enough, right?) So Doctor'd up this little guy, drilled a hole in a cup, put the fuel line to it, then filled her up with gas....it's gotta work, right? Nope, same symptoms.
Next, I pulled off the carbs pulled out all the jets and the pilot. Everything was already clean, but I cleaned it anyway. I then switched all the parts, including the floats, float bowls and diaphragms from one carb to the other....Nothing!
I'm guessing its gotta be the valves...I mean, I hope its the valves!
cFogs out
BT
NNNN
Attachments
cgguy09
1971 CB350 K3
Also, let me describes these symptoms more clearly:
when I pull on the throttle, both butterflies both butterflies lift evenly. But the left cylinder is not "banging" until it gets a little higher on RPMS or until its running a little longer.
When I lift the butterflies one at a time (individually, not through the throttles), the right cylinder runs great, good consistent smooth bang bang. But when I lift the left it hesitates, then kicks in, and doesn't seem to run as smooth.
Compression on both cylinders is ~160. Right plug is a good tan. Left is soiled.
I've switched the coils and gotten the same results.
Any other ideas, other than valve gap?
when I pull on the throttle, both butterflies both butterflies lift evenly. But the left cylinder is not "banging" until it gets a little higher on RPMS or until its running a little longer.
When I lift the butterflies one at a time (individually, not through the throttles), the right cylinder runs great, good consistent smooth bang bang. But when I lift the left it hesitates, then kicks in, and doesn't seem to run as smooth.
Compression on both cylinders is ~160. Right plug is a good tan. Left is soiled.
I've switched the coils and gotten the same results.
Any other ideas, other than valve gap?
cgguy09
1971 CB350 K3
Redliner said:...you mean to tell us that you went on adjusting the carbs before even doing the chain tension and valve adjustment?!
Pick a corner and sit.
My friend has my feeler gauge! I'm making him bring it over when he's done with work. ( I know that sounds like my dog ate my homework, but I had the afternoon off & wanted to eliminate the jets/carbs/floats/etc)
Cam Tension is good...
Redliner
Over 1,000 Posts
1. Why bother trying to adjust carbs at all without cam chain and valves first? (in that order) Edit: Ah...
2. Fouled plug? Swap the jets from one carb to the other. Somebody may have bored one out.
Do your pilot screws have rubber o-rings on them? Is the choke butterfly on right? (just look at them and see. Trust me, shit happens) You should have two jets in each carb, the smaller of those two should have a plugged jet. Even and strong spark on both? Is the plug wet with oil? Stick your finger in each one and lift the slide a bit. Is the slide in the carb returning to the closed position and making a "knock" sound every time? If it's not knocking, there's too much resistance.
2. Fouled plug? Swap the jets from one carb to the other. Somebody may have bored one out.
Do your pilot screws have rubber o-rings on them? Is the choke butterfly on right? (just look at them and see. Trust me, shit happens) You should have two jets in each carb, the smaller of those two should have a plugged jet. Even and strong spark on both? Is the plug wet with oil? Stick your finger in each one and lift the slide a bit. Is the slide in the carb returning to the closed position and making a "knock" sound every time? If it's not knocking, there's too much resistance.
Remove both carbs, remove all jets. Spray carb cleaner through one jet and repeat on the same jet from the other carb. Do they spray the same or very different?
Repeat for other jets and then do the same thing with each drilling in the carb body or float bowl. Compare one to another. Repeat for each and every hole you can see in the carbs. One of the jets or passageways is blocked.
Repeat for other jets and then do the same thing with each drilling in the carb body or float bowl. Compare one to another. Repeat for each and every hole you can see in the carbs. One of the jets or passageways is blocked.
cgguy09
1971 CB350 K3
The cafe gods have smiled upon me (and were probably laughing). So my buddy was unable to locate my feeler gauge he borrowed 2~3 weeks ago, but as a good man he replaced my tool with a better one. I got everything in place, took off the alternator cover and the point cover, and loosened the hold-nut for the exhaust valve for the right cyclinder immeadately I noitced the nut was way too easy to move. When I loosened the nut, it of course moved the valve, so I was unable to determine the exact space dialed in but my guess is that it was about .15~.2mm out of spec (way way out of spec) from where I was able to test it...
Put it to spec, then tested the inlet and tested the left cylinder...everything else was perfect. I started it up and it ran like the day it rolled off the line in Japan.
When I first noticed problem I took off the point cover and gave it a quick inspection too look for any obvious problems with the points or valves & didn't notice anything. My guess is the nut shook itself loose enough that I it wasn't visably loose but loose enough to allow the valve gap to change overtime.
Admittedly, I probably would have checked the valve gap last anyway. But had I still had my feeler gauge, I would have defintely checked before pulling & cleaning and switching the carb parts or going to the lengths I did ensure fuel flow...The moral of the story is don't lend your tools out for more than 30 minutes at a time.
At the very least, I now know I have: good fuel flow, super-clean carbs, and a full swear jar.
Big thanks for the help guys, redliner, crazy PJ, Kanticoy, et al. I really do appreciate it. Someday, in heaven or hell I'll buy you guys a round.
Take care guys.
Put it to spec, then tested the inlet and tested the left cylinder...everything else was perfect. I started it up and it ran like the day it rolled off the line in Japan.
When I first noticed problem I took off the point cover and gave it a quick inspection too look for any obvious problems with the points or valves & didn't notice anything. My guess is the nut shook itself loose enough that I it wasn't visably loose but loose enough to allow the valve gap to change overtime.
Admittedly, I probably would have checked the valve gap last anyway. But had I still had my feeler gauge, I would have defintely checked before pulling & cleaning and switching the carb parts or going to the lengths I did ensure fuel flow...The moral of the story is don't lend your tools out for more than 30 minutes at a time.
At the very least, I now know I have: good fuel flow, super-clean carbs, and a full swear jar.
Big thanks for the help guys, redliner, crazy PJ, Kanticoy, et al. I really do appreciate it. Someday, in heaven or hell I'll buy you guys a round.
Take care guys.
cgguy09
1971 CB350 K3
Redliner said:
Yea, my bad for setting out without having all the toolds needed at my disposal. But you gotta work when you can find time, right?
(and again, I got a 6 pack and a new Sears Craftsman Feeler gauge out of it...for the old autocraft set that wasn't worth a 6 pack of PBR)
