Uploaded November 2020 | Updated September 2026, 2 weeks ago
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Question 1: 1974 CB550 1/8th throttle hesitation, trouble getting the throttle response smooth.
Answer: Important to know where your AIR SCREW mixtures are at. Look at stock spec for turns out. If you are needing to go way out or way in from specs then take into account the exhaust modifications that are done. The need to go up or down on the idle jet may be needed. More turns out on mix = larger idle (or a very clean circuit)
More turns in = Need for smaller
GET THE CARB SYNC DIALED IN!
Cody’s suggestion on sync kit : amzn.to/35YMchj
Pilot jet explained - howtomotorcyclerepair.com/how-to-size-your-pilot-jet-pilot-screw-explained
Question 2: 1976 CB750F Crank breather routing after airbox delete
Answer: A hose routed back and down attached to a mini pod filter attachment is most common. I have seen others leak it into an oil catch. Both require draining or cleaning regularly.
Question 3: 2004 VFR800 Poor throttle response at higher RPMS before V-Tech response. Insight on homebrew remedies like the “flapper valve delete and pair check valve modification”
Answer: Cody or Matt have not seen of a silver bullet answer or remedy for this issue. Make sure you have a clean airbox with a stock filter before any modifications. Check spark plugs and learn how the engine is currently operating. If any modifications are done. Try one at a time, not all at once. LET US KNOW WHAT YOU DECIDE/OUTCOME!
Question 4: 1999 CB750 Nighthawk, Jetting insight for a slight stumble off idle on acceleration. A K&N air filter is currently being used.
Answer: Three things you can try.
1. Go back to a stock air filter and see if any difference is made with the bike a proper operating temperature.
2. Turn all of your pilot mixtures (fuel trim) to a half or even full turn out. RPM may increase so adjust accordingly.
3. Bump the idle jets up to a larger size. If #35 is stock try going to a #38 or #40. You could also try a #4 washer shim tune on all of the vacuum slide needles.
*Full carb teardown/cleaning and modifications can be found inside of MotorcycleMD’s “Inline Four Carb Cleaning Workshop”
Here is the link. themotorcyclemd.com/pro-carb-cleans
Enjoying The Broken Moto Show?
You can now show your support by
BUYING US A BEER!
howtomotorcyclerepair.com/codymattbeer
Thanks!
Submit questions to: askbrokenmoto@gmail.com
motorcyclemd.com
howtomotorcyclerepair.com
Question 1: 1974 CB550 1/8th throttle hesitation, trouble getting the throttle response smooth.
Answer: Important to know where your AIR SCREW mixtures are at. Look at stock spec for turns out. If you are needing to go way out or way in from specs then take into account the exhaust modifications that are done. The need to go up or down on the idle jet may be needed. More turns out on mix = larger idle (or a very clean circuit)
More turns in = Need for smaller
GET THE CARB SYNC DIALED IN!
Cody’s suggestion on sync kit : amzn.to/35YMchj
Pilot jet explained - howtomotorcyclerepair.com/how-to-size-your-pilot-jet-pilot-screw-explained
Question 2: 1976 CB750F Crank breather routing after airbox delete
Answer: A hose routed back and down attached to a mini pod filter attachment is most common. I have seen others leak it into an oil catch. Both require draining or cleaning regularly.
Question 3: 2004 VFR800 Poor throttle response at higher RPMS before V-Tech response. Insight on homebrew remedies like the “flapper valve delete and pair check valve modification”
Answer: Cody or Matt have not seen of a silver bullet answer or remedy for this issue. Make sure you have a clean airbox with a stock filter before any modifications. Check spark plugs and learn how the engine is currently operating. If any modifications are done. Try one at a time, not all at once. LET US KNOW WHAT YOU DECIDE/OUTCOME!
Question 4: 1999 CB750 Nighthawk, Jetting insight for a slight stumble off idle on acceleration. A K&N air filter is currently being used.
Answer: Three things you can try.
1. Go back to a stock air filter and see if any difference is made with the bike a proper operating temperature.
2. Turn all of your pilot mixtures (fuel trim) to a half or even full turn out. RPM may increase so adjust accordingly.
3. Bump the idle jets up to a larger size. If #35 is stock try going to a #38 or #40. You could also try a #4 washer shim tune on all of the vacuum slide needles.
*Full carb teardown/cleaning and modifications can be found inside of MotorcycleMD’s “Inline Four Carb Cleaning Workshop”
Here is the link. themotorcyclemd.com/pro-carb-cleans
Enjoying The Broken Moto Show?
You can now show your support by
BUYING US A BEER!
howtomotorcyclerepair.com/codymattbeer
Thanks!
