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CB750 Barn find project - First Timer
Underdog1:
--- Quote from: Rob62 on August 26, 2018, 10:30:57 AM ---This kind of fault can be difficult to diagnose.... if its fuel starvation and you go through all the various components to ensure they aren’t blocked or damaged you will eventually eliminate it. For an electrical fault it will also be a process of eliminating the faulty component. If an electrical component is damaged, cracked, broken etc as it warms up it can lose connection then as it cools it reconnects.... so the only real way to diagnose it is to replace components one at a time until you solve the problem. The condensers are so cheap they should be changed anyway, if that works then its a cheap result... i would suspect the coils but it could be anything. Does it stop dead or begin to missfire and die gradually?
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It dies gradually, seems like it’s not pulling properly and then stops acellerating but will maintain speed if I stay on the throttle, as soon as the throttle let off it dies.
I’m going to order new condensors, I assume the DS repro ones are ok? What about his repro coils?
Rob62:
The gradual thing doesn’t sound electrical to me..... I have new ds condensers on my k4, one of them failed after 50 miles (missfiring and spaarking like hell under the points cover) so I can’t recommend those... I’m wondering if its fuel or worse still mechanicsl. Have you checked valve clearances and compression?
Underdog1:
--- Quote from: Rob62 on August 26, 2018, 02:39:56 PM ---The gradual thing doesn’t sound electrical to me..... I have new ds condensers on my k4, one of them failed after 50 miles (missfiring and spaarking like hell under the points cover) so I can’t recommend those... I’m wondering if its fuel or worse still mechanicsl. Have you checked valve clearances and compression?
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Set the valve clearance when I rebuilt, haven’t checked compression but everything was within spec,barrels were honed and rings replaced.
Could be fuel flow as I’m getting random carb bowl overflows.. will have time tomorrow to check it all.
I’ve got a hondaman ignition module to go on but I want to have it running sweet before I add more things into the mix
Rob62:
Ps if you want repro coils try the ones from wemoto......much cheaper and work well i can vouch for those!
Rob62:
Check compression! Burned or leaky valves could be an issue.... build up of carbon on the stems can cause the valves to stay open once warmed up (i had this issue back in the 80’s)... a re-lap of the valve seats transformed the motor. A compression test will help, when cold and also at running temp... keep going, you will get there.
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