1980 Jetting help

[aperfcrcle]

Hey guys. I inherited a 1980 from my uncle who was no longer able to ride and I am trying to get it back to running correctly. I have done a bunch of research on the topic, but all posts seem to get differing opinions and never a real definitive answer.

The bike currently has a 6-2 Kerker with K&N pods (3 pods with chrome back) - I know this will be met with dislike but I want to keep to bike the same as it was my uncles and he loved it in its current state.
125 mains, 35 slows, appears to be stock needles stamped 55A with a shim washer on top, and mixtures screws out 2 turns.

I took the carbs apart and blasted everything out and everything is clean now. Upon inspecting the plugs, they are covered in black soot - so it is clearly running too rich. Funny thing is - 1 of the carbs mixture screws had 2 rubber o-rings in it, and that plug looked perfect!! I was in talks with Bill from Tim's and he has been super helpful on getting me parts. I ordered the Stage 3 kit from him thinking the bike wasn't jetted properly and that's why it was popping, etc. Now with pulling the plugs, I am skeptical about adding a 130 main if the 125 is clearly too rich.

My questions are:
- Should I keep the 125 Mains in the bike and just adjust the mixture screw to 1 and 1/2 as a starting point to attempt to match the good spark plug with 2 o-rings?
- Should I keep the 125 Mains and upgrade the slow to a 38 as I have read a few instances that has helped tremendously with pods?
- Should I add the Stage 3 Needles and keep the 125 mains and upgrade to a 38 slow?

Any help would be greatly appreciated! Thanks in advance.

[Rick Pope]

Do you know when the carbs were last removed and totally stripped down for cleaning and replacing all the rubber (Viton) bits? If not, start there. A bike that old will have lots of carb issues, and as fiddly as it is to get it right, chasing your tail with leaky carbs is an exercise in futility. The fact that you found two O-rings on one mixture screw is a strong clue that a complete teardown is in order,

If you're going to do the carbs yourself, get Mike Nixon's book and parts from Randakk or one of the other suppliers who support this forum.

[daves79x]

Rick's advice is good - you must verify that the carb bodies are perfectly clean and all passages are open. The pressed-in #35 jets need to be removed to clean them properly. With pods you can benefit from drilling them to #38 or replacing with #38.

I have jetting VB62 carbs for pods and started with 125 mains (Keihin). The bike ran very well, but was just too lean with those jets. I went to 130 Keihin and that is just about perfect. Two turns out on the mixture screws. No shims under the needle. That could be part of your problem.

I would not install the Dyno-Jet stuff. You can jet just as well with Keihin jets. I'd also verify that your choke is not hanging.

There are volumes written here about jetting carbs for pods. You can search to find the posts.

Dave

[aperfcrcle]

Hey guys, thanks for the answers. The bike was purchased from Mr. CBX in 2020, everything was cleaned out and rebuilt then. It was sent back to them twice to have the jetting done. The bike starts and runs no problem, just running rich but I still took them apart to give it a good cleaning. Slows have been tapped out and cleaned, I ordered new float needles as they were little sticky and not springy, etc. The reason I took them off was because it was popping and backfiring out of the back of the air filters under very slight throttle, and clearly running rich.

I am just trying to get a good starting point to put it all back together. It seems like the consensus would be to take the shim off the stock needle, go to 38 slows and keep the 125 in with 2 turns out.

[SanDogDewey]

You can try cleaning those float needles. I’ve had good luck with the ultrasonic cleaner. Soak in lacquer thinner.

[daves79x]

The popping and backfiring is rather an odd symptom of carb issues. It rarely occurs because of the carbs. Valves not seating or burned more commonly causes this. What do you know about the general engine health? The bike with pods should NOT be to rich with 125 Keihin mains. Now if they are aftermarket or Dyno-jet 125s, all bets are off. 125 Keihin and 125 Dyno-jet mains do not flow the same rate. It's hard to diagnose without knowing exactly what you have.

Dave

[aperfcrcle]

Just wanted to update / close this thread out for anyone in the future having similar questions - as I also hate when I am searching for answers and threads get left abandoned with no real answer.

The bike is up at running very well with TIMS dynojet kit. The needle clip is set on the 2nd from the top as suggested with the directions, mixture is 2.5 turns out. Main jet is the Dynojet 130, and I also stepped up on the the idle jet to a 38 which has really helped with cold starts in my opinion. Still running the K&N 2 into1 pod filters as well. I also synced the carbs using the digisync and all of the popping I mentioned in the last post is gone. Power delivery is very smooth, plugs are clean after a few hundred miles. Hope this helps anyone in future! Thanks to Dave as well for his advice.

Have a few more parts to throw back on - but here's how she sits today!

[daves79x]

Glad to hear it's working for you!

Dave

[NobleHops]

Great job, well done. That bike looks sweet.