SOHC.co.uk Forums > CB750
Acceleration Misfire
Johnwebley:
If the needle jets are worn,it's likely to make it to rich,
Try dropping the needle by one groove, see what happens
I assume you have the standard air box and filter?
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McCabe-Thiele (Ted):
Have you eliminated the possiblity that its coil or plug lead related rather than suspecting the Boyer unit?
As has been said if it was worn needles that would make it run richer then you might expect that to be reflected in the spark plug colouring. Are you using resistor plugs or just resistor caps. Are the spark plugs relatively new?
If you have the points base & advancer might be worth returning the ignition back to standard temporarily - easier than having to take the carbs off. (Never seen a Boyer Unit so not sure they are)
Saesneg Shaun:
--- Quote from: McCabe-Thiele (Ted) on September 19, 2024, 10:06:50 AM ---Have you eliminated the possiblity that its coil or plug lead related rather than suspecting the Boyer unit?
As has been said if it was worn needles that would make it run richer then you might expect that to be reflected in the spark plug colouring. Are you using resistor plugs or just resistor caps. Are the spark plugs relatively new?
If you have the points base & advancer might be worth returning the ignition back to standard temporarily - easier than having to take the carbs off. (Never seen a Boyer Unit so not sure they are)
--- End quote ---
Yes, I checked them all and trimmed back and loose ones. I checked the connections on the boyer ignition and just to be sure the kill switch and ignition switch. I'm running resistor caps and non-resistor NGK plugs.
Unfortunately I had issues with the points cam running out of true hence going to boyer electronic.
Skoti:
--- Quote from: Saesneg Shaun on September 19, 2024, 08:31:54 AM ---
--- Quote from: Skoti on September 19, 2024, 07:13:00 AM ---On the other hand you may have the same problem that I had.
Needle jets worn and guttered out, giving a massive flat spot when accelerating.
Honda part number 16012 392 004
--- End quote ---
I hadn't considered that. The bike has 33k miles on it but their probably the originals in there. Is there any obvious visible signs of wear I can look for or just replace?
--- End quote ---
The originals in mines had done 23k.
Held up to the light along with the new ones you will probably easily see the wear difference.
Good luck.
Skoti
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