So I have had a couple of local folks look at the carbs on my 1980 CBX rebuild. The last complete carb rebuild got the bike running and it runs well past 3K rpm. Off the line the bike bogs down and stalls, but if I feather the clutch and get the bike moving it absolutely runs great.
Wondering if the group could throw some ideas out there to help.
Thanks in advance
Carb Rebuild Complete - Bike bogs on start
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bbrock585
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- Location: London Ontario Canada
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daves79x
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Re: Carb Rebuild Complete - Bike bogs on start
They need rebuilt correctly next time. The low speed circuitry is almost surely partially plugged and your accelerator pump likely does not work as well. Very few guys know how to get these right the first time - including your 'local guys'. They have to come apart again. I'll give this advice again - if you decide from the beginning that you are going to pay someone good money to do your carbs, for heaven's sake, why not have one of the proven guys do them? You'll be money and time and aggravation saved.
Dave
Dave
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bbrock585
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Re: Carb Rebuild Complete - Bike bogs on start
Dave appreciate your input - the journey of learning continues
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RJ CB650
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Re: Carb Rebuild Complete - Bike bogs on start
How does it respond to choke? Properly tuned, when you apply choke it should also have an rpm increase. If applying choke causes it to bog/stall on idle, it means that running too rich, not necessarily a "blocked circuit" which I have seen as the default answer and from my experience with CBX and other CV carbed bikes, not always the problem.
Either way, it is clearly the low speed circuit. As Dave said, this style of carbs need special expertise that only comes from experience working with them. Much like a tradesman, getting them working correctly is not a matter of teaching, but of experience. Having the hands on experience and ear to get them running perfect. It could be incorrect jetting and adjustment as well if that had been tweaked during rebuild or in the past. Did the service document or make log notes of them during the rebuild?
Other options can also include vacuum leaks or even a fueling issue. Add to that (this from personal experience) that a CBX can seemingly be running well down a cylinder or two and without a baseline of a solid engine, the above 3k running strong might not actually be strong! Have you had previous experience or was it running smooth in past? It could even be ignition off somewhere as well. Slightly fouled plug can cause problematic spark giving this as well.
Overall, lots of advice, but it does require a step by step diagnosis and inspection to verify the true cause. So back to the top, start with how does it idle (what RPM) and how does it respond to choke? Do all six cylinders warm up evenly or at all? This is most safely checked with a light spritz of water onto the exhaust header lightly. Won't harm anything, no different than hitting a small puddle. Start it up cold, and go down the cylinders. They should get sizzling hot evenly.
Either way, it is clearly the low speed circuit. As Dave said, this style of carbs need special expertise that only comes from experience working with them. Much like a tradesman, getting them working correctly is not a matter of teaching, but of experience. Having the hands on experience and ear to get them running perfect. It could be incorrect jetting and adjustment as well if that had been tweaked during rebuild or in the past. Did the service document or make log notes of them during the rebuild?
Other options can also include vacuum leaks or even a fueling issue. Add to that (this from personal experience) that a CBX can seemingly be running well down a cylinder or two and without a baseline of a solid engine, the above 3k running strong might not actually be strong! Have you had previous experience or was it running smooth in past? It could even be ignition off somewhere as well. Slightly fouled plug can cause problematic spark giving this as well.
Overall, lots of advice, but it does require a step by step diagnosis and inspection to verify the true cause. So back to the top, start with how does it idle (what RPM) and how does it respond to choke? Do all six cylinders warm up evenly or at all? This is most safely checked with a light spritz of water onto the exhaust header lightly. Won't harm anything, no different than hitting a small puddle. Start it up cold, and go down the cylinders. They should get sizzling hot evenly.