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can anyone diagnose this problem

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jyed
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can anyone diagnose this problem

Post by jyed on Sun 11 Dec 2016, 12:42 pm

just got my hands on a cb and absolutely stoked, looking to do a full rebuild. when started up with choke on and can hear a pretty rough rattling noise, turn choke off and seems to get worse then dies. 
i can't post the video link as  I'm a new member but if you youtube "cb500 engine rattling. dies when choke turned off"


any suggestions of where to start to rectify the problem cheers.
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teamster1975
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Re: can anyone diagnose this problem

Post by teamster1975 on Sun 11 Dec 2016, 12:51 pm

Is it firing on both cylinders? Check to see if both down pipes are getting hot for starters.
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eternally_troubled
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Re: can anyone diagnose this problem

Post by eternally_troubled on Sun 11 Dec 2016, 4:22 pm

Well I had a look at your video (I think it's this one https://www.youtube.com/watch?v=6k-WxETyILU ).

I'd guess that your idle carb settings are way off, which is why it needs the choke on to run - unfortunately I can't tell why your carbs settings are way off it could be a number of things (off the top of my head):

1. perished carb rubbers letting air in
2. perished carb seals/gaskets letting air in
3. throttle plates out of sync
4. gunked up petrol blocking up one or other air drilling or jet in the carb

If you don't know when the carbs have been last cleaned/overhauled I'd suggest taking the off and giving them a good clean/overhaul as per the workshop manual (if you haven't got one you should get one).  While you are there it might be worth replacing some bits by using an overhaul kit...

Also:  this forum is mainly for the '97 - '03 water-cooled CB500 :)

muttley1
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Re: can anyone diagnose this problem

Post by muttley1 on Sun 11 Dec 2016, 5:51 pm

What he said, clean the carbs / jets / floats
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jyed
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Re: can anyone diagnose this problem

Post by jyed on Mon 12 Dec 2016, 2:00 am

Appreciate the feedback and advice guys cheers! -@:9 didn't realise that about the forum! Will search for a more appropriate one cheers
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teamster1975
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Re: can anyone diagnose this problem

Post by teamster1975 on Mon 12 Dec 2016, 2:36 pm

jyed wrote:Appreciate the feedback and advice guys cheers! -@:9 didn't realise that about the forum! Will search for a more appropriate one cheers

We'll always help where we can, a bike is a bike after all.
If you don't get any luck else where please feel free to ask here Smile
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madsundaysurvivor
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Re: can anyone diagnose this problem

Post by madsundaysurvivor on Wed 14 Dec 2016, 7:22 pm

also look for cracks in rubber manifolds and  in the membrane of vacuum piston carburetor..... Rolling Eyes
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Vardypeeps
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Re: can anyone diagnose this problem

Post by Vardypeeps on Wed 28 Dec 2016, 12:21 pm

Posted the same when I got my 1995 CB500 around June/July and it was the faithful clutch rattle that most old CB's seem to have?
If it's really rough and loud it's most likely the clutch basket, if it's more tinny and metallic sounding (faster paced) it could be your cam chain tensioner.

May have just cut out as the idle needs to be increased?

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