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74' CB450 running on one cylinder?

2K views 7 replies 5 participants last post by  Sonreir 
#1 ·
The CB has been acting up, bogging and stalling. Initially thought it was fuel related but was just guessing, then left carb started dumping fuel from left carb overflow. Yanked carbs yesterday and got that stuff sorted, took it for a short ride today. Ran fine for about 3 miles or so then seemed to bog/lose power, stalled it once but it made it back home with it feeling as though only on one cyl. Got it back to the shed and the right muffler was much cooler than the left even though the headers on both sides was to hot to touch for long. Just looking for ideas or what I should check first. Typing this I am wondering if could be gas cap vent problem but probably not if a cylinder is dropping out. Thanks
 
#3 ·
I did pull that plug and it looked dry but maybe it was firing right before I shut it down so the gas burned off? I also had some backfiring when I was having the issues.
 
#7 ·
If it was running ok beforehand I'd say its unlikely to be anything other than the problem carb, or the fuel supply to it. Unlikely to be the tank vent if its only affecting one side - imho.

I'd recommend going back and having a closer look at the carb - check in particular the fuel lines and float valve, and float level.

If all looks good there, maybe also worth checking that the flow rates between left and right carbs are the same. Easiest way I've found to do that that on the 450 is to turn the fuel off, drop each float bowl in turn, place a suitable container (or funnel) below the carb, turn the fuel tap on and measure/compare the rate/volume of fuel collected for each. Anything unusual there, go back and strip the fuel tap to check for dirt, and then check the routing of the individual hoses.
 
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