September 15, 2019

Honda CV Carb – anybody know there way round them ?

Honda CV Carb – anybody know there way round them ?

Long story – kind of stuck on getting the Cb450 running right. She’s a ’72 bike;, with the original Keihin CV Carbs. Complex bloody things – made worse by 45 years of wear and tear. I’ve stripped the carbs and cleaned them – many times – and rebuilt them with new gaskets and jet kits.

Where they’re at currently is the bike starts and runs ok, pulls really well from the midrange and on up – but – the air mixture screw still isn’t working properly on one side. Makes it hard to get a smooth idle, and to me, the bike feels lumpy and generally unhappy pulling off idle. Not the worst problem in the world, but it’s bugging me that it’s not right,

According to the manual:

“Next, adjust your “air/mixture screws”. Usually, 3/4 turn out from full in will be a good place to start. Adjust back and forth for maximum rpm, on each carb. If you end up at some extreme, like all the way in or 3 or 4 turns out, you have a problem somewhere in the carb – probably indicates a good cleaning is in order. These carbs must be kept scrupulously clean to work properly.”

One side works as described above – but on the other, the screw does bugger all until it’s almost all the way home, and then you get maximum rpm when it’s fully closed.

I’ve swapped the needles around, put the old ones back in, tested the damn thing for air leaks by spraying carb cleaner on the outside, but can’t make any headway at all – the screw on that side just doesn’t seem to be adjust the mixture the way it should.

Anybody any pointers or steers on anything else to try from here ?


Source: Honda CV Carb – anybody know there way round them ?

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