Topic: CB350F Won’t Idle, loses power and dies in first gear. Misfire?

[zcb350fb]

Hi everyone. I have a 1973 Honda CB350F that had a leaky carb. I cleaned and rebuilt the carbs and took it to a shop to have the carbs properly sync’d. I also cleaned the gas tank and rebuilt the peacock around this time. This happened a month ago. Ive had the bike since June 2017 and it has always ran great besides the leaky carb that it developed around Christmas time. Any ways, I got the bike back from the shop and it ran great. I took it on a 2 hour ride. At the end of my 2 hour ride, the bike started making a deeper exhaust noise and had a loss of power. The previous owner told me he had some trouble in the past with cylinder four not firing. I pulled over in an empty parking lot, unplugged the cord from the 4 cylinder spark plug and plugged it back in. I let the bike sit for 10 minutes. I fired the bike back up and it was fine. The normal exhaust note was back and it had all of its power.

A week later i went for a quick ride and 10 minutes into the ride, the deeper exhaust note returned with the loss of power. I attempted limping the bike home but the bike started to not idle. I would get the bike in neutral and give it gas to keep it idling. When i would put the bike in first, the bike would die. I waited on the side of the road for my brother to come pick me up. When he got there, he got on the bike, gassed the hell out of it in high revs and was able to make it through all of the gears but he really had to give it gas to do so and it still would not idle. We decided to trailer the bike home at that point since it was dark, even though it seemed that it had gotten a little better.

I am thinking this is an electrical issue since i just had the carbs cleaned. I am going to check the spark plugs, the timing, and even the vent on the gas cap. I just wanted to see what everyone else’s thoughts were on this issue. I am really hoping it is not a carb issue again. Thank you in advance!

[Mr. Mike]

Well Z,

If it were me, I’d start my investigation going backwards. The bike you say ran great last year despite a leaky carb. OK, that remedied, your troubles worsened in what sounds like a fuel issue to me. Your brother “gassing the hell out of it” to keep the rev’s up seems a clue. Have you opened the drain screws on all four carbs to see what shows? Quite possible a blockage in the connecting tubes, or, a clog in; 1) filter if one is used, or 2) junk in the carb somewhere seeing how they’ve recently been taken apart.
Did you “clean the tank” and “the petcock” after the sync job? If so, recheck those things.
Check each plug wire for spark. Put a good plug in the wire and ground it and crank the motor. Then check for fouled plugs.

Eliminate the fuel issue and spark, then move on. You do have sufficient fuel right?

[zcb350fb]

Thanks for the advice. I do have sufficient fuel. It is non ethanol 93 octane that I’ve always put in it from the same station. The tank was cleaned and peacock was rebuilt days before the carbs were cleaned and also before the carbs were synced. I will check the drain plugs on the carbs to see what comes out. There is a fuel filter in the line. Kits about a month old. It’s a little bit of a different design than the one i had on it prior. The new filter has only been ran on the bike the last month. I have read where guys had issues with filters and where some guys don’t even run filters on the bike. Ill let you know how it goes!

[zcb350fb]

The fuel filter is about a month old. “Kits” was a typo

[Mr. Mike]

Is the newer filter directional? Look for an arrow on the filter body. It points in the direction of fuel flow (to the carbs).

[zcb350fb]

Yep it’s directional and I’ve got it the arrow going towards the carbs. This filter has a golden spongy material rather than paper. The last one had paper. Maybe the spongy material isn’t porous enough?

[Mr. Mike]

Z,

Hopefully you’ve made some progress on your issue.
The filter; can you see into the plastic body? If so, is there any junk or weird colored material on the inside? Kinked hose anywhere?
If this filter is suspect in any way, just remove it and see if your trouble clears...you’ll know soon enough.

[zcb350fb]

Hey man. It was the fuel filter. I took the new one of and tried blowing through it on both ends and it wouldn’t let anything through. I read on here that the spongy filter material on the inside of it is actually metal. Maybe bronze? And it gets clogged up a lot faster than mesh or paper. Guess i better clean my tank again. I had a little flash rush=t after i cleaned it the last time and thought that it would be ok. Anyways i put a new filter on that was the same design as the old one and its working fine.

Thank you for the advice and guidance. I. Still going to put new plugs and points on the bike though. It cant hurt and who knows the last time they were changed

[Mr. Mike]

Thanks for reporting back...and on a positive note at that.
Sometimes the simplest of things bite us when we think we “did it right” and send us on a trip to Frustration Island for a short spell.

Yeah check/replace the plugs, but I wouldn’t get too crazy now, just enjoy it for a while, weather permitting (seeing how it “ran great” prior to this episode).