SOHC.co.uk Forums > CB750
Acceleration Misfire
Nurse Julie:
To this day Mark Paris is still insisting screw in for more air, screw out for more fuel. Anectodal and personal experience on 750's and all other non PD SOHC /4 carbs, is that out gives more air, in gives more fuel. If we had set the screws on our own builds and bikes as per Marks advice, the bikes wouldn't have run. Regular riding of all our bikes by ourselves and all our customers bikes, prove we have done it correctly.
McCabe-Thiele (Ted):
Sounds as if Mark Paris is getting confused between when an engine is running rich and when it is running weak.
If he has those concepts reversed then he is correct.lol
Back in my youth I used to think a hot tail pipe exhaust meant it was running too rich my Dad put me right it took me a while for the penny to drop. After all too much fuel it would burn hotter no?
He was right of course when it's rich the exhuast gases are cooler at the tail pipe - in a way it defies logic if you ignore what's taking place inside the engine and how the petrol actually burns.
Saesneg Shaun:
Haven't been out much on the bike but got the chance to ride today. I tried turning the air screws in a bit but no difference to the bogging down unfortunately. Slightly richer means it won't idle cleanly unless I up the tickover speed to nearer 2000rpm so i'm guessing 1 1/8th turns out is about right. Also tried spraying the inlets with brake cleaner but no air leaks either.
The I rule out the more i'm beginning to think its electrical and the boyer ignition is to blame. Its happening between 2000-3000 rpm in all gears.
Skoti:
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
Saesneg Shaun:
--- 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?
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