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I've just got a 1980 CX500 and it's my first, hence the question.



The bike was stood for quite a while before my purchase and ran/idled roughly under 1500 revs but ran much better above that mark.



I stripped the carbs down and found the usual gunk and also cleaned out the tank and added an in line filter from tap to carb.



Eventually, she fired up and seems a lot better. However, she still seems a little rough at idle but runs like a dream above 1500 revs.



Any ideas?



Ta.
 

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It can take several goes to get the carbs right.It's the low speed idle circuit that gives most problems in them.Two of it's venturi are underneath the infamous,"Black Banana" so click here,



http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=19&t=140



But the float heights and no carb boot leaks have to be right on as well as per,



http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=19&t=110



See this thread as well,



http://cx500forum.com/index.php?/to...__96690__hl__guitar__fromsearch__1#entry96690
 

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Welcome to the forum. Please take a few minutes and fill in your location and the model bike you have in your profile. It will help others that may be living near you if you ever need help.



The idle issue is a normal side effect of a plugged or restricted low jet. Carb spray won't clean it out enough to fix the problem. You need to use a micro drill bit to clean it. .018" #77 is the size you need to clean it out. Usually I recommend pulling the jet with an EZout. But it can be done without pulling it if you have something to hold the tiny drill bit.



This shows the low jet in the center between the two main jets.





This is the low jet that's effecting the idle issues.





It's also possible to solder the drill bit to a paper clip so you can get it down inside without pulling the jet out.





Again, welcome to the forum.

Larry
 

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Welcome to the forum. Please take a few minutes and fill in your location and the model bike you have in your profile. It will help others that may be living near you if you ever need help.



The idle issue is a normal side effect of a plugged or restricted low jet. Carb spray won't clean it out enough to fix the problem. You need to use a micro drill bit to clean it. .018" #77 is the size you need to clean it out. Usually I recommend pulling the jet with an EZout. But it can be done without pulling it if you have something to hold the tiny drill bit.



This shows the low jet in the center between the two main jets.





This is the low jet that's effecting the idle issues.





It's also possible to solder the drill bit to a paper clip so you can get it down inside without pulling the jet out.





Again, welcome to the forum.

Larry


Larry,



I too am experiencing the low idle blues with fluctuations of 500 rpm even after doing a "good" clean with ultra-sonic 5 months back.



Sometimes she'll start (always very easily) and idle at 1100 nicely until warmed up. Sometimes she'll start and idle at 1500 'til warmed up then fluctuate between 1500-2000 and 'Sometimes" drop back to a steady 1500 and sometimes fall to my desired 1100rpm. I just isn't consistent.



When I do run 1100 it feels as if the left cylinder misses, but not always. Plug color on L and Right are fine, maybe a tad rich, but better than lean. Valves are spot on, but still louder than I'd like.



Air leaks seem non-existent and I've also recently done the plug cap brass rod replacement



I would like to follow your expert advise and clean all air passages and low jet orifices with drill bits as you describe. HOWEVER, I am running a Gl400 with VB38A Carbs which do have a smaller venturi. Do you think drill bits of the size you recommend for the 500cc bikes are suitable for my carbs as well? Or am I going to have to go with a hit or miss situation and hope a cause no damage as these are fairly rare, at least around here (Thailand)



Thanks for the specific advise to my question and to all other general carb etc related question others post.



Regards,



Mark in Thailand
 

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Mark,

I would expect that the low jets for a 400 might be a bit smaller. The 500 and 650's use a #45 low jet. If you pull out the low jet and it's a #45 then it will be the same .018 drill bit. But if it's a #35 or smaller then you'll need to get a micro drill set and start at the smallest bit to clean it out slowly. Then go up to the next size drill and see if that one cleans out more debris. Don't force it. If it wont go in fairly smooth and feels like your hitting the brass from the beginning then it's too big.



If it were me I would pull the jets to see what size they are first. BUT, you need to make sure you get a good quality EXout. I wouldn't have a clue what company to send you to over there. So go with the best tool company you know of.



If you still have debris floating around in the bowls and it's blocking the low jet occasionally then it would account for the erratic idle speeds. You probably set the idle with the low jets still being slightly restricted or plugged. So when the idle goes down it's probably when one side is being blocked. When the idle is high it's passing all the gas it needs and is firing both cylinders.



Larry
 

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Mark,

I would expect that the low jets for a 400 might be a bit smaller. The 500 and 650's use a #45 low jet. If you pull out the low jet and it's a #45 then it will be the same .018 drill bit. But if it's a #35 or smaller then you'll need to get a micro drill set and start at the smallest bit to clean it out slowly. Then go up to the next size drill and see if that one cleans out more debris. Don't force it. If it wont go in fairly smooth and feels like your hitting the brass from the beginning then it's too big.



If it were me I would pull the jets to see what size they are first. BUT, you need to make sure you get a good quality EXout. I wouldn't have a clue what company to send you to over there. So go with the best tool company you know of.



If you still have debris floating around in the bowls and it's blocking the low jet occasionally then it would account for the erratic idle speeds. You probably set the idle with the low jets still being slightly restricted or plugged. So when the idle goes down it's probably when one side is being blocked. When the idle is high it's passing all the gas it needs and is firing both cylinders.



Larry


Thanks Larry for the timely reply.



I'll search around here for a proper micro drill set and EXout.



Wish I had an extra carb set to send to you to have them done up properly by the "Master" himself. Mail back here to me might be prohibitively expensive, but friends could bring in their baggage. Also, Customs would probably think they were new and not used and charge an arm and a leg just to get them out of their hands. Tax on postage too. Oh well.....



Thanks again
 
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