The Broken Moto Show: Episode 8

The Broken Moto Show - EP8 - Gas in engine oil/airbox and Engine modifications

Submit questions to: askbrokenmoto@gmail.com
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Question 1: 1976 CB550F my bike is running rich and there is gas in the airbox.
Answers:
Pressure check the float valves. This will help you see that even with the correct float height at spec, the float needle can still be compromised.
How to pressure check float heights with gas.
* https://youtu.be/Bxx5Iw1xoVw

If the air filter is really old and has rotted from gas going into the air box or from old age. A brand new air filter may breathe better allowing the bike to lean out with the better airflow.
- Check compression
- Sync carbs with a quality carb sync set.
- Cody’s recommendation on a sync set - https://amzn.to/3itFpAo
- Use quality parts for your carb rebuilds.
Carb rebuild video for the 550: https://www.howtomotorcyclerepair.com/cbcarbrebuild/

Question 2: 1982 CB750c Cam timing issue. TDCC vs 360 degree rotation.
Answer: We can all agree that going by the book is the best option. Double check that you are in the right stroke TDC vs TDCC. If you are checking on the exhaust stroke, valve timing can read “in spec’ on intake clearances and tight on exhaust.

Question 3: 1981 CB900c Induction has been modified to remove the four carb system to a 2 carb system, What are some ways to modify the motor to get more power.
Answer: Open up the wallet and pay someone for some quality head work. Port and polish the head to get better flow in and out. Look into cylinder boring and bigger pistons. You definitely need to fix the dead 105psi cylinder. That will also improve your power. Lightening up the bike can also help.

Question 4: 1979 Honda CM400A “Hondamatic” Gas in the oil as well as some ride-ability issues pertaining to throttle input.
Answer: You need to do a complete carburetor overhaul. Potential float valve issues, idle circuit problems, accelerator pump problems, ect. Rip those carbs out and clean them, replacing parts with as much quality stuff as you can get.