trojanjohn
CB750 New member
Hey there awesome people. John from little ole England here,
Im looking for a little help with a fueling issue to the carbs. So, my sons 1981 DOHC, he's on active duty in Afghan and I promised him Id get it running sweet before he returns in November. Its bored out to 823cc because I had to, Wiseco pistons. k and n pods, Delkevic 4 into 1 exhaust, not baffled. Dynojet stage 3 kit. whole engine re built. Carbs stripped cleaned ultrasonically twice. Acceloraters all new, as are floats valves needles and jets. Great spark on all 4, timing is good. great compression, great leakdown test results. Custom tank with 5mm petcock outlet (quality after market pet cock listed for cb750s) and as you know, 8mm fuel pipe into the carbs between no 1 and 2. Bench synced. Idles and revs in the workshop lovely. Valve clearances check and re checked.
No matter what i do i am constantly getting rich to very rich plugs at 1 and 2 perfect at 3 and lean to very lean at 4. could it be that I'm low on fuel delivery as I'm now asking for more than the petcock can deliver with the bigger bore and stage 3 kit ???.
I have a slight leak on carb boot no 1 and when sprayed with starter fuel she bogs down rather than increases in revs, as you would expect if rich. Also when I pull the choke while riding she bogs down. All fuel pipes checked, no blockages. Idle screws all at 3 1/2 turns.
Having never had an engine bored before, or fitted a stage 3 kit, i was wondering if fuel delivery is an issue?
Really looking forward to some knowledge from you good people. Much respect.
Im looking for a little help with a fueling issue to the carbs. So, my sons 1981 DOHC, he's on active duty in Afghan and I promised him Id get it running sweet before he returns in November. Its bored out to 823cc because I had to, Wiseco pistons. k and n pods, Delkevic 4 into 1 exhaust, not baffled. Dynojet stage 3 kit. whole engine re built. Carbs stripped cleaned ultrasonically twice. Acceloraters all new, as are floats valves needles and jets. Great spark on all 4, timing is good. great compression, great leakdown test results. Custom tank with 5mm petcock outlet (quality after market pet cock listed for cb750s) and as you know, 8mm fuel pipe into the carbs between no 1 and 2. Bench synced. Idles and revs in the workshop lovely. Valve clearances check and re checked.
No matter what i do i am constantly getting rich to very rich plugs at 1 and 2 perfect at 3 and lean to very lean at 4. could it be that I'm low on fuel delivery as I'm now asking for more than the petcock can deliver with the bigger bore and stage 3 kit ???.
I have a slight leak on carb boot no 1 and when sprayed with starter fuel she bogs down rather than increases in revs, as you would expect if rich. Also when I pull the choke while riding she bogs down. All fuel pipes checked, no blockages. Idle screws all at 3 1/2 turns.
Having never had an engine bored before, or fitted a stage 3 kit, i was wondering if fuel delivery is an issue?
Really looking forward to some knowledge from you good people. Much respect.