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Newbie
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Discussion Starter · #1 ·
Hey I gotta 86 Radian (yx600), so far ive removed the air box, changed out the factory main jets (97.5) and gone to a 125 across all four. Ive also changed the pilot jet from (30) stock to a 32 , whats happened is the bike was running like a charm after a carb sync, and fine colour tune on the fuel/air in the low to mid range and as soon as I hit high way speeds 105 to 106 Km an hour (roughly 65 mile hr) she would start to act like almost like its not getting enough gas, and if I added a passenger the bikes acts up even more naturally. Now after alot of fussing around I came to realize the low end of the bike seems to be to rich due to the smell of gas coming from it after a long ride and just sitting idleing, so the idea was brought to my attention check the needle jet inside the throttle piston for adjustable slots. So I took the carbs apart again for the 40th time so it would seem and must of got lucky found that the needle jets were adjustable and set on the middle setting of 6 so I moved them all up one reinstalled and ran a colour tune once again and took it for a drive, I noticed a few big things the low to mid speed ran way worse then before ( especially after it heated up to full temp being air cooled) but the high way speed was now normal no burping or acting up while I was riding. I didnt try a couple things I think I should have
1. I didnt resync maybe that had something to do with it il try it
2. I wasnt sure how much I was supposed to clamp down the screws holding the spring on top of the needle jet inside the throttle piston (<- could that have something to do with it? is the needle jet supposed to have a little play in it or be firm unmoveable?)
3. Would you happen to know if 125 is a good setting to go on the jets?
any suggestions or ideas would be much appriciated.
thanks
 

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Level III Kludger
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16 Posts
Hey NewtoCustoms! Welcome to CF.

I don't know much about the specifics of your bike's carb, but I owned and rode an 81 Honda CB650 for about four years. It also had tricky carbs. It does sound like a carb sync might help.

Some other basic things I might check:

Is there a separate idle circuit screw? Sometimes there's an idle screw that's separately adjustable-- usually you don't even need to take apart the carb to get to it. (On my bike, the PO had cranked these way out and made the engine idle too rich)

Is your air filter clean and in good working order? What happens if you take out the air filter and do a test run? Maybe it's a fuel/air mix issue.

Are the vacuum tube holes (where you might put a carb sync tool) plugged properly? If even one has lost its cap, you could have disastrous problems.

Have the valves been adjusted recently?
 

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Newbie
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Discussion Starter · #3 ·
hey thanks for replying man, first off my carbs are Mikuni BS30 C series carbs, the airbox is no more infact its in 10 pieces lol, currently I have it set with I think the equivalent of stage three jets, meaning my orginal factory jets were
main: 97.5 , pilot jet (or low speed jet) 30. There now at Main: 125 , pilot jet 32 , I ve also dropped the jet needle one notch to restrict the gas flow at full throttle or high ways speeds. with the c serious carbs or (constant vacuum) carbs, they pretty much rely on the air box to control and regulate the negative air around them but there has to be a way to jet these carbs and make them run faster I guess its just chase my tail time like ive been doing for about a month now lol. Before I dropped the needle jet a notch the bike was running great at the low to mid range (a little rich but great) but as soon as I got into the high range or highway speeds it would start to almost make a blurp blurp noise once in a while but as soon as I came onto the gas it would pick right up confusing now that the needle jets been dropped down a notch the high way issue seems to be fixed but the low to mid has been affected and seems to run a little worse especially after the bikes warmed up, Naturally since the engines tend to be a little lean apon first running then start to go towards a bit rich after heating up. Im more or less looking for suggestions, as far as I know the vacuum on the carbs are fine the diaphragms on the top of the carbs looked fine no cracks or wear the boots that meet from the engine to carbs look good and all the caps on vaccuum parts of the carbs where you would sink seems to be in place properly lol as I said im really confused :-S
 
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