cb450 running too rich

305 nutt · Post by **305 nutt** » Tue Jun 09, 2009 8:37 pm

I have a cb450 that is running way too rich. I've rebuilt the carbs, soaking them in berryman carb cleaner over night, installed new points, condensor, timed, set valves. Fires right up, runs great until you get it under a load and it rolls black smoke, suits up the plugs on both sides. I have checked the jet sizes with the book and they are correct. This was a fairly unmoldested bike with 17k miles on it. Runs sweet above 3500 rpm, but below that she falls on her face and runs like crap. 2 possibilities I'm thinking after messing with the carbs for 4 days now, possibly valve adjustment, or slides installed in opposite carbs. The only thing I could see making a difference in the slides are they have 2 holes drilled in them down in the bottom, I'm assuming to control the lifting of the slides? I have never had a set of carbs stump me like this, but I need help this time. thanks nutt

Nomad · Post by **Nomad** » Wed Jun 10, 2009 9:05 pm

I dont have a suggestion for you but wanted to say you got me thinking about my own carb issue no idle and fouling one plug then the other , but your line about having the slides in backwards hit a note , you can not put them in backwards ... unless you put them in the opposite carb , BINGO! the generic Honda service manual states the side of the slide with the arch goes towards the air cleaner , checked mine today and yep they were wrong , swapped and OMG! it runs good again ! dang Keyster carb kits with no instructions ,, also it shipped with 86 jets not the 98 I was planning on ( they flipped them over when they packed them ) OkI do have some suggestions :
1 make sure the carbs are sealed to prevent air leaks , new O rings and gaskets help also if you have a crushed carb insulator remove and wetsand on a pane if glass (flat surface) .
2 make sure the petcock screen is clean ,seals are tight and gas flows freely , if using inline filters watch for tight bends and air bubbles also I have run into pinholes and cracks in the float bowl
3 sync the slides put the air cleaners on then adjust the carbs , they like the resistance of air cleaners
4 make sure the fuel cap gasket does not block the tiny vent hole , stops the bike dead, if it is rusty and full of crap use a compressor and blow into the vent hole , the cap will pop apart .
5 fill the tank with good gas , these old bikes are sensitive to ethanol gas that is old

as you can guess I ran into issues with each of the above , each one alone may not stop you but they do add up and all work against you .. the 450 is a sweet ride keep at it and you will be happy with the results . (<>..<>) Nomad