Topic: How important is the air filter restriction on the carbs?

[Ved]

I'm working on a 1977 CB750A and the air filter box is missing so I ordered some POD cone type air filters that seem to have little to no air restriction at all. I literally had to tape off 80% of the surface area of the air filter surface area to create enough vacuum so it would pull fuel, and run. I can get it to start quite easily when choked with no problem, and it idles perfectly, but when I throttle her up to around half throttle it dies out like its starving for fuel. I checked each bowl and the floats are doing their job. Filling up nicely, and shutting off, no leaks. Upper and lower jets have been meticulously cleaned and are flowing fine. Pilot screws are at the factory setting of 1 turn out. I can't seem to find the sweet spot on the air restriction so it winds out without dieing.

Any thoughts?


~Ved

[campbmic]

Your going to have to rejet and possibly move the needle up or down. Theres a lot of threads on the forum about it. Its a real pain rthat I'm in the middle of going through right now. The best thing you can do is oull the bike until it starts to cut out, then pull the clutch in, hit the kill switch, and coast to your shop and take your plugs out.

If they are white its lean and if they are super dark and sooty/wet its too rich.

[Old Scrambler]

I would strongly advise to get the stock air-box.  The A-carbs are smaller than other models and very touchy to run smoothly at road-speed with the auto.  Pods are for go........not cruise!

[Ved]

Thanx for the quick response guys. I called a local motorcycle junker/collector here and he has an air box for me..10 bux.  I just need to get a filter for it he said. 

Also, on a side note... Could the accelerator pump be part of the problem too? When I cleaned the carbs all I did were the jets and the float needle, but  never did check the darn acc pump on the carb. The lower jets were completely clogged, but upper jets weren't so bad. I bet that acc pump on the carb has a clogged hole as well.

[scottly]

I think that solenoid you mentioned on another thread is for the accel pump on A models..

Edit: just looked at the manual; think I was mistaken. Sorry!

[Ved]

The solenoid valve does not connect to the acc pump.

Throttle opener solenoid


Throttle Opener to solenoid valve location


Accelerator pump.