On my 73 RD350, I noticed while the bike was idling, you could hear a distinct difference in the firing from the left cylinder, which seemed to hit harder, to the right. I also noticed a little hesitation at about 1/4 throttle only around 5k rpm.
I pulled the plugs and sure enough, the left color was a nice dark tan, and the right was a wet looking brown. I know its running on both cylinders, so the right isnt dead. I checked the points and botj were perfect, they are new daichi points and new hvc condenser. The carbs were synced a couple hundred miles ago.
I saw one topic talking about the old plug caps going bad, and I have new coil sets but was contemplating going to a vape ignition, so I havent put them on.
I also saw a post elsewhere a out drilling out the larger ball on the filter side of the carb to clean behind it, then tapping it for a screw to seal it up.
I cleaned the points, and was going to throw new plugs at it, and check the plug caps
Are there any other big things I could be missing? Could the things I mentioned be my issue?
When were the carbs last cleaned? When they were cleaned were they completely disassembled (were the needle jet tubes removed and thoroughly cleaned)?
Are the pilot jets new? If not, when were they last removed and cleaned?
Are the air screws set at the same number of turns out on each side?
Have you verified that float height is in spec and the same for both sides?
The carbs got stripped and cleaned when I bought the bike about a year ago. Since it had sat. They weren't super bad, but got totally pulled apart. The jets and needle are all new where I changed them for the chambers I put on about 8 months ago. Also has new viton tip float needle and seats.
I verified the air screws not long ago as well and they are the same.
I could double check the float height again.
With the carb bowls off it's super easy to pop out the emulsion tubes and give them a once over just to be certain they're spotless. :thumbs:
While you're in there might be wise to verify that the needle clips are on the same groove. Probably OK, but I've had bikes come to me for carb troubleshooting or carb cleaning that were different L to R.
So I pulled and cleaned the carbs. The left float level was a couple mm high. Pulled the emulsion tubes and checked all the passageways and they were clear. Threw in new plug too. I will update again once I get to ride it. I am chasing a drivetrain issue as well that I will likely post about elsewhere
Always fully disassemble the carb. Then either throw it in an ultrasonic cleaner or spray with carb cleaner and compressed air. I usually have a brass brush on hand to clean. Small wire bristles will help with small holes.
Quote from: quocle603 on September 16, 2025, 07:32:24 PMAlways fully disassemble the carb. Then either throw it in an ultrasonic cleaner or spray with carb cleaner and compressed air. I usually have a brass brush on hand to clean. Small wire bristles will help with small holes.
I dont have an ultrasonic, but I do always use carb cleaner. I keep an assortment of wiring and old cables for small passages.
Quote from: Vintagewannabe on September 16, 2025, 09:55:06 PMQuote from: quocle603 on September 16, 2025, 07:32:24 PMAlways fully disassemble the carb. Then either throw it in an ultrasonic cleaner or spray with carb cleaner and compressed air. I usually have a brass brush on hand to clean. Small wire bristles will help with small holes.
I dont have an ultrasonic, but I do always use carb cleaner. I keep an assortment of wiring and old cables for small passages.
Not everyone does. To be honest, I have always had good luck with just really cleaning it with some cleaner, wires, and taking my time on them. Then ultrasonic just helps by setting it and forgetting for a duration of time. Still need to clean them but not as much. Most people say they clean them but don't remove the emulsion tube, which can be a source of running issues. Good luck!
Started the bike up, and it sounded crisp, sounds better than before. My new problem is the left carb started absolutely pouring out of its overflow. I am hoping I somehow put something back in wrong, because this is the carb that I had to do the most adjusting on the float arm. I think it was at 17, and I brought them both back to about 16
Sounds like youre on the right track. Your float must be stuck, try tapping it or clearing out what is causing the gas to continue to flow. Your float height may be a factor, I would just check the fuel valve/plunger seat.
Quote from: quocle603 on September 17, 2025, 10:55:05 PMSounds like youre on the right track. Your float must be stuck, try tapping it or clearing out what is causing the gas to continue to flow. Your float height may be a factor, I would just check the fuel valve/plunger seat.
I tried tapping it, but I think I'll have to pull it. Just didnt have the time.
Ive never had luck with tapping it. Just something that everyone does, worth a shot. Youll be riding in no time.