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Discussion Starter · #1 ·
hi all new to the site and what a great site it is,and boy am i glad i found you guys..i just got a 1980 cx500c the bike did not run when i got it a week ago so far i have cleaned the carbs, did the old pine-sol trick like we do on the old cb's , replaced the plugs, hot wired the key switch, got the bike to start but runs a tad rough,heres the kicker soon as i touch the throtle it dies almost like theres a air leak sprayed alround the boots no leaks getting plenty of gas none adjustable floats but checked with a clear tube they both stop about 1cm from the top of the float bowl, i have not synced the carbs yet due to fact the wife put my meter upside down and it leaked out so waiting on that, but my next ? is the bike came with no air filter can that be my issue i have ordered one but wont be here till next week any help opr idea's will be greatful
 

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You should have an air filter,,but I think you may have other issues.



I am not sure but to me I think the gas level 1 cm below the bottom of the float bowl may be too low. As you said the floats are not adjustable.

When you had the carbs apart did you check to be sure the small spring loaded pins in the end of the float needles were not seized?
 

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Discussion Starter · #3 ·
You should have an air filter,,but I think you may have other issues.



I am not sure but to me I think the gas level 1 cm below the bottom of the float bowl may be too low. As you said the floats are not adjustable.

When you had the carbs apart did you check to be sure the small spring loaded pins in the end of the float needles were not seized?
yes the spring pins are free and clear go do down and spring right back, the rubber tips are soft when i said 1 cm from the top of the float bowl i meant it's 1 cm from the joint where the bowl meets the carb body... is there any only manuals on this site for downloading ?
 

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That level may be just a tad low, but that isn't what causing your problems. Have you inspected the vacuum pistons for ease of rising? You can just reach thru the choke butterfly and raise them with you finger. They should rise soothly and easily and return back to the lowered position smoothly.



You said you did the Pine Sol cleaning trick. Describe a bit more the things you did. Did you remove and clean the jets and the emulsion tubes under them? Did you remove and clean the idle mixture screws and make sure the washer and O ring were intact? Did you remove the "black banana" and verify that all the passages actually allowed carb cleaner and compressed air to enter at one spot and flow out of another? These carbs like a lot of attention if they get grungy. If you keep clean fuel and maybe a stabilizer in them they will remain clean for many years. But you have to get them that way first.
 

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Discussion Starter · #6 ·
That level may be just a tad low, but that isn't what causing your problems. Have you inspected the vacuum pistons for ease of rising? You can just reach thru the choke butterfly and raise them with you finger. They should rise soothly and easily and return back to the lowered position smoothly.



You said you did the Pine Sol cleaning trick. Describe a bit more the things you did. Did you remove and clean the jets and the emulsion tubes under them? Did you remove and clean the idle mixture screws and make sure the washer and O ring were intact? Did you remove the "black banana" and verify that all the passages actually allowed carb cleaner and compressed air to enter at one spot and flow out of another? These carbs like a lot of attention if they get grungy. If you keep clean fuel and maybe a stabilizer in them they will remain clean for many years. But you have to get them that way first.
removed all 4 air cut offs , removed the 4 jets 115 mains/78 slow ? not sure if them are the right size don't have the book yet, the floats and float needles, air mix screws, the vacuum pistons slides that black thingy that sits under the the piston cap, soaked them in pin-sol for 3 days, ran a e- string thru all the holes i could used carb cleaner came out all the places it should, cleaned and polished the needle seats the emulsion tubes are clean along with the jets, today i got my float level tool and the floats are sitting and 15.5 mm but the same thing happens starts up but soon as you touch the gas it dies

the bike sounds great long as you don't touch the gas and yes i blew them out with air
 

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removed all 4 air cut offs , removed the 4 jets 115 mains/78 slow ? not sure if them are the right size don't have the book yet, the floats and float needles, air mix screws, the vacuum pistons slides that black thingy that sits under the the piston cap, soaked them in pin-sol for 3 days, ran a e- string thru all the holes i could used carb cleaner came out all the places it should, cleaned and polished the needle seats the emulsion tubes are clean along with the jets, today i got my float level tool and the floats are sitting and 15.5 mm but the same thing happens starts up but soon as you touch the gas it dies

the bike sounds great long as you don't touch the gas and yes i blew them out with air
not sure why you have 4 acv,s......you probably have more money than us porpers


i think you have one of three issues

1 blocked airfilter

2 airleak at carbs or airbox

3 not enough fuel in the bowl.





hook a clear pipe[Blues tip] to your drain nipple,run up along side your carb and see where your actual fuel level is
 

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Discussion Starter · #8 ·
not sure why you have 4 acv,s......you probably have more money than us porpers


i think you have one of three issues

1 blocked airfilter

2 airleak at carbs or airbox

3 not enough fuel in the bowl.





hook a clear pipe[Blues tip] to your drain nipple,run up along side your carb and see where your actual fuel level is
lol sorry typed 4 instead of 2 i just got done with my cb 750 carbs so i must been think of them when i typed that the fuel stops just tad below the joint of the carb body and the bowl, no air leaks aroun the boots eng sid or airbox and well i'm waiting on a air filter from bike bandit but right now it dont have one in it
 

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You will find the downloadable manuals HERE The Quick Reference thread in the General Discussion section has tons of helpful information in it.



Joel in the Couve
 

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Does it make any difference if you have the choke on when you give it some throttle?



Have you ever got it to rev up beyond idle?



Did you check to see if air/carb cleaner or what ever you were using came out the 3 holes in the venturi of the carb when you sprayed it into the idle jet?



Sorry,,more questions, no answers, but this seems like a strange problem.




You could try running it with the sight tubes on the carb drains to see if fuel is getting into the carbs fast enough.
 

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Discussion Starter · #12 ·
Does it make any difference if you have the choke on when you give it some throttle?



Have you ever got it to rev up beyond idle?



Did you check to see if air/carb cleaner or what ever you were using came out the 3 holes in the venturi of the carb when you sprayed it into the idle jet?



Sorry,,more questions, no answers, but this seems like a strange problem.




You could try running it with the sight tubes on the carb drains to see if fuel is getting into the carbs fast enough.
it don't matter if the choke is on or off soon as i twist the throttle it starts spitting and sputtering for a sec then dies, yes the carb cleaner does come out the holes, the sight tube shows gas is at the joint, of the bowl and the body of the carbs they both are even, last night i glued the boots into the air box(nice thing about having the bike in your dinning room)you can work on it when you want but anyhow i'm leaning towards a air leak but i just dont know because the bike don't rev or die when i spray the boot rubbers, yes i did have it rev up twice by easying the throttle but it did not last long
 

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Discussion Starter · #13 ·
cancan someone tell me what the air mix screw should be set at everything on the bike is stock,when i got the bike it was set at 2 turns out from set but it's turning my plugs black then black and you can smell it running rich but glueing my boots did the trick as far as getting it to rev up,(even tho i hooked the throttle cables up backwards, bike sounds great will hit 9K in a hurry to but if you know off hand what the air mix shoulld be set at please help me out and thank you all for helping me with this
 

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cancan someone tell me what the air mix screw should be set at everything on the bike is stock,when i got the bike it was set at 2 turns out from set but it's turning my plugs black then black and you can smell it running rich but glueing my boots did the trick as far as getting it to rev up,(even tho i hooked the throttle cables up backwards, bike sounds great will hit 9K in a hurry to but if you know off hand what the air mix shoulld be set at please help me out and thank you all for helping me with this
general thoughts.......2 1/2 turns out is correct......to start with
 

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Ignore the reference to Electronic tacho.Just use around 1100 Rpm and turn out 2.5 times,not 2 times.



Note.Due to age anomalies sometimes the idle mixture screws are not linear so once initially set it''s best to go for a ride with a Plug spanner/wrench and check the plug colour and re-adjust.You are looking for a Tan coloured plug.



HTH
 

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I am beginning to have doubts that the carbs are causing this problem.




I think it might be time to start testing the stator or CDI.



It still could be a fuel issue but after reading everything you have tried I think you should be able to get it to rev above idle.



If it were me I would try unplugging the 3 yellow wires coming from the stator that plug into the RR under the seat to rule out a problem in the charging windings. If it works better with that unplugged, it is a stator problem.



If that makes no difference then I would test the AC voltage on the low speed winding, the white wire in the plug with the blue and white wire coming from the stator and plugged into the cdi.



Do a search for stator resistance test, there should be lots of posts.
 

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Discussion Starter · #17 ·
ok in fast past i lost my notes and forgot what jet goes where the jet under the emulsion tubes should be what? i got 78 and 115 jets
 

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The 115 goes in the brass fitting, the 78 goes into the other hole.
 

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Discussion Starter · #20 ·
OK got the carbs back on, runs great while sitting, still having a stumble issues around 3k rpms, switch gears it goes away, go to get on the throttle again about 5k she bogs down so bad that rpms drop to 2k let off she'll drive smooth but can't get her over 40mph? WHY check float level its 15.5 mm.......used wd40 to check for air leaks, no change of eng sounds
 
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