Hey guys, my roommate has a disc brake variant CB350 that we have been working on for a few weeks now trying to get it road worthy so he can learn to ride around in a parking lot before the cold season really sets in. It is his first bike and I feel bad at this point because he is very new to bikes and in fact has never even been on one. But instead we are always working on it and not doing what he really wants to be doing, which is learning to ride.
So, what we have done is rebuild the front brake system as the piston was seized in the caliper, works reasonably well, still need to bleed it again. Fit new tires and tubes, cleaned the carbs and replaced all rubber, needle and jets...except the one jet that is hidden under the little black plug, not sure which jet this is. And actually one of the little plugs is missing and one was stuck, also were not included in the keyster kits. Probably should have address that before reassembly... Then we correctly routed the throttle cables and turned the idle mixture screws 1 turn out from seated.
The bike fired up first kick after putting everything back together. However, the idle was high at around 3500, after some fiddling we adjusted the throttle cables so the idle is approx 1500, and the slides seem to rise at same time. The idle is kinda inconsistent and drops or raises slightly, just a few hundred rpms, especially after opening the throttle and watching the needle come back down, but then sometimes it is fine and stays right at 1500. After, we got it idling decently, I took it down the street to see how it would do, and it immediately started backfiring, especially on the left side. It will not rev past 4500 or so and acceleration becomes very poor. After turning it off the left header is hot but not as hot as the right...
Here's the rest of the story, I am sure it is very lean, as the p.o. has put some open shorty mufflers and had no airboxes at all, with stock jets. We have ordered some stock airboxes, instead of pods. So, I would think that a lean condition would cause the backfiring, but what about not revving past 4000-5000? Ignition timing or the advance mechanism? I remember my KZ would backfire and not rev past 3500 when I first got it and it turned out the ignition advance unit was rusted stuck.
What size jets do you guys run after putting on more free flowing exhaust, but with stock airbox? Thanks for any help!
-Joe
So, what we have done is rebuild the front brake system as the piston was seized in the caliper, works reasonably well, still need to bleed it again. Fit new tires and tubes, cleaned the carbs and replaced all rubber, needle and jets...except the one jet that is hidden under the little black plug, not sure which jet this is. And actually one of the little plugs is missing and one was stuck, also were not included in the keyster kits. Probably should have address that before reassembly... Then we correctly routed the throttle cables and turned the idle mixture screws 1 turn out from seated.
The bike fired up first kick after putting everything back together. However, the idle was high at around 3500, after some fiddling we adjusted the throttle cables so the idle is approx 1500, and the slides seem to rise at same time. The idle is kinda inconsistent and drops or raises slightly, just a few hundred rpms, especially after opening the throttle and watching the needle come back down, but then sometimes it is fine and stays right at 1500. After, we got it idling decently, I took it down the street to see how it would do, and it immediately started backfiring, especially on the left side. It will not rev past 4500 or so and acceleration becomes very poor. After turning it off the left header is hot but not as hot as the right...
Here's the rest of the story, I am sure it is very lean, as the p.o. has put some open shorty mufflers and had no airboxes at all, with stock jets. We have ordered some stock airboxes, instead of pods. So, I would think that a lean condition would cause the backfiring, but what about not revving past 4000-5000? Ignition timing or the advance mechanism? I remember my KZ would backfire and not rev past 3500 when I first got it and it turned out the ignition advance unit was rusted stuck.
What size jets do you guys run after putting on more free flowing exhaust, but with stock airbox? Thanks for any help!
-Joe
your pilot jets are below those plugs and have to be cleaned or replaced(a strand from a wire brush and soak it in wood alcohol might clear it)..the plug has to be in place for the idle circuit to work correctly,,,one thing you didn't mention was any adjustment to the air screws.....which control the mixture at idle!! are the diaphrams(top) still good and flexible and no cracks,,,DON'T worry about your jetting, 68-70 primary and 105 -110 secondary(105 stock will run any street exhaust and open carbs)......good luck
