hard_y_rd
XS650 Guru
Thanks for sticking with me on this 5twins, I will try to get my idle sync adjusted better and go from there.
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How many turns is too much
- Thread starter hard_y_rd
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- carburetors
hard_y_rd
XS650 Guru
Another thing. I was watching a youtube vid on idle mix adjustments and if the screws are turned all the way in it should kill the engine. I had mine in 1/4 of a turn with no diff. Didn't turn them in all the way but if it doesn't kill the engine that means that it is running too rich. I will try that too to see if the jets are off.
XS650D
XS650 Junkie
5 twins,if after adjusting floats and idle sync and one side is too many turns out to get to the sweet spot is it ok to up the pilot on one side only or will that screw other parts off the fuel circuit,
CDNTX650
XS650 Guru
Not really, something is amiss with that pilot cct or screw or carb, need to figure out what.
Posted via Mobile
Posted via Mobile
Yes, something is amiss. Jets should be the same size and mix screws should dial in pretty much the same on both sides. I mentioned float level a couple posts up. This is critical. It's not something you usually need to mess with on a newer bike but these usually need it checked. Remember, you must check the float from both sides, measure twice, because many of these are twisted on the mounts. That can throw the fuel level all off. You may have one side at spec but if the other float "bulb" is sitting higher or lower, who knows what the fuel level will end up at.
hard_y_rd
XS650 Guru
Quoting myself now, kinda funny. Anyway, wasn't getting any change in idle with the mix screws even though the idle screws were a bit amiss like 5twins pointed out. So i cranked them all the way in to see if that would kill the engine but it doesn't. The idle runs better there which points to the jets being too rich correct? Just wondering where to go from where i'm at. Should i drop a jet size on both pilot and main and put my clip position to stock?
What i don't understand is why it wasn't fouling the plugs if it was too rich?
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XS650D
XS650 Junkie
What do your plugs look like,straps,any carbon on end ring,r they the same color after a run or afetr say 10min idle,have u fed some fine wire thru the pilot circuits ,carb cleaned and blown compressed air thru,did the air and fuel cleaner come out somewere or did it load up and shoot back at u,i had one float that ws totally clogged even though i installed a new pilot jet something was wrong,ran a wire and sure enough it was clogged solid on one side,the design on thease old carbs can cause issues very easy if any dirt/rust in tank or old fuel ect.I am having same problems with one side running lean even after cleanin them many times,somtimes clogs from a 40 year old bike in really small orfices can not be opened and cause major headaches.Have u cheaked the butterfly seals by spraying some starter fluid at both sides ect,Mine were totally shot and even after changing them the shafts must be worn as they still suck air on the inside,i thing oversize orings r in order now as new shafts arent available.A really good point by 5 twins regarding the possibly of twisted floats is something to look for and something i am going to look at on mine,goodluck.
You have to be pretty rich to foul plugs. You may just be a little too rich. The early carbs were set up richer from the factory. You may not need much, if any re-jetting for minor mods. Yes, go back to stock and see what happens. You also have to keep in mind that today's gas isn't much like the stuff from years back. That could make stock jetting too rich even.
hard_y_rd
XS650 Guru
I went back to stock jetting today, unfortunately i stripped a float bowl screw. The one under the choke body. Gonna patch it up until i can get the proper helicoils. I took the lock washer off and put some locktite on it. There were enough threads to catch. Haven't had time to get the carbs back on yet. Will post back with the results.
hard_y_rd
XS650 Guru
Stock jetting with needles at stock clip height. Mix screws in all the way still doesn't kill engine. Downsize on the jets?
Could be that your carbs are simply too open to be drawing fuel from the idle port, possibly drawing from the transfer ports instead. Can you back off the idle stop screw(s) to fully closed, then open with only a quarter turn, and get it to run?
Reference: http://www.xs650.com/forum/showthread.php?t=34864
Reference: http://www.xs650.com/forum/showthread.php?t=34864
hard_y_rd
XS650 Guru
I will try that tomorrow. P.O had 120 mains in there. I put them back to stock.Don't know which direction to run. Would high test gas be the culprit?
hard_y_rd
XS650 Guru
So your idle screws are 1/6th of a turn from closed? Even with my throttle cables detached, i can't get the arms to go back that far to touch the idle stop.
Attachments
Good! Yeah, you back-out that idle screw 'till the throttle arm stops. That's when the butterfly valve is fully closed and seated. From that fully-closed position, run the idle screw down 'till it just touches the throttle lever arm, then go an additional 1/4 turn, for starters.
From that fully-seated position up to about 1/2 turn of the idle screw, most of the fuel delivery comes from just the idle jet, controlled by your mix screw. Any more open than that and fuel delivery is mostly coming out the transfer ports (those other tiny holes between the butterfly plate and the slide). The transfer ports also get their fuel from the pilot jet (in the bowl), but are not affected by the mix screw. It only controls that one idle port, the one closest to the engine.
The purpose of the transfer ports is to provide smooth fuel delivery during the throttle transition from idle to lower mid-range (controlled by the jet needle).
Optimum carb setup is to have the idle fuel delivery provided by just the singular idle jet, with just barely enuff vacuum signal to keep the transfer ports on the edge of delivery, ready to jump in and prevent off-idle stumble. If everything's in good tune, with proper idle, the carb's will be in that position, as they were designed for...
From that fully-seated position up to about 1/2 turn of the idle screw, most of the fuel delivery comes from just the idle jet, controlled by your mix screw. Any more open than that and fuel delivery is mostly coming out the transfer ports (those other tiny holes between the butterfly plate and the slide). The transfer ports also get their fuel from the pilot jet (in the bowl), but are not affected by the mix screw. It only controls that one idle port, the one closest to the engine.
The purpose of the transfer ports is to provide smooth fuel delivery during the throttle transition from idle to lower mid-range (controlled by the jet needle).
Optimum carb setup is to have the idle fuel delivery provided by just the singular idle jet, with just barely enuff vacuum signal to keep the transfer ports on the edge of delivery, ready to jump in and prevent off-idle stumble. If everything's in good tune, with proper idle, the carb's will be in that position, as they were designed for...
hard_y_rd
XS650 Guru
Ok good. Understood. Seems like my cables "hang" when i give it throttle sometimes.You have to push the idle stops by hand sometimes. Might have to lube those cables better. Give er another go sometime today.
It's funny i was reading the clymer and on page 22 no.4 paragraph it says that stock high speed jet is 130. It says to install a 140 to enrich or 120 to lean it out. It doesn't mess around with in between or half sizes.
If i can't get any response from stock jetting, I might try the 120. Don't know if i can afford to take the float bowl off with my bad float bowl screw.
It's funny i was reading the clymer and on page 22 no.4 paragraph it says that stock high speed jet is 130. It says to install a 140 to enrich or 120 to lean it out. It doesn't mess around with in between or half sizes.
If i can't get any response from stock jetting, I might try the 120. Don't know if i can afford to take the float bowl off with my bad float bowl screw.
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The Clymer manual people probably weren't that 650 carb savvy. They put out many manuals and some of their advice or instructions is somewhat "generic". 130 up to 140 or down to 120 is 5 jet sizes. That's a lot. Sure, someone may need to lean or richen their carbs, but not 5 sizes on the mains worth. Re-jetting the stock 650 carbs for mods is pretty well documented. In most cases it only requires one to a couple sizes larger. If you have straight open pipes, that may make a perfect tune difficult.
hard_y_rd
XS650 Guru
I'm not trying to be a smart ass but my case kinda goes against the documentation. Is it common practice to downsize your jets from stock for mods like uni's and straight pipes? Thought it was the other way around. I just want to get this running right.
i'll have to round up some smaller mains and pilots and try that.
i'll have to round up some smaller mains and pilots and try that.
No, it's not common to have to downsize, but every case is different. Some things to keep in mind are you have early carbs that were set up richer than later sets from the factory. Also, those straight pipes. They don't call them "drag" pipes for nothing. They improve power only up near, at, or above red line, hurt it everywhere else. Needing to run smaller than stock jets is telling you that. You've de-tuned your motor.
Another factor could be worn needle jets. Over time, the needle can wear the hole in the needle jet oval. Or, if the carbs were badly gummed up at one time and sat that way for a while, that gas varnish can actually eat the jet away inside. In either case, the jet gets bigger and richer running.
Another possibility is you just haven't run the bike enough and far enough to get good color on both plugs. If the way it runs seems OK, you may want to just put a few hundred mile on it. When your jetting is very close, sometimes that's what it takes to uncover the little glitches. Running the bike under all conditions, slow, fast, hard and easy acceleration, etc. may show little trouble areas that one quick road test won't.
Another factor could be worn needle jets. Over time, the needle can wear the hole in the needle jet oval. Or, if the carbs were badly gummed up at one time and sat that way for a while, that gas varnish can actually eat the jet away inside. In either case, the jet gets bigger and richer running.
Another possibility is you just haven't run the bike enough and far enough to get good color on both plugs. If the way it runs seems OK, you may want to just put a few hundred mile on it. When your jetting is very close, sometimes that's what it takes to uncover the little glitches. Running the bike under all conditions, slow, fast, hard and easy acceleration, etc. may show little trouble areas that one quick road test won't.
That could be misaligned/catching butterfly plate, possibly caused by worn throttle shaft holes. Some info here, these oughta keep you busy:
http://www.xs650.com/forum/showthread.php?t=27566
http://www.xs650.com/forum/showthread.php?t=28547
http://www.xs650.com/forum/showthread.php?t=29452
http://www.xs650.com/forum/showthread.php?t=32499
http://www.xs650.com/forum/showthread.php?t=33692
Here's 5Twins procedure for clearing the pilot circuit:
http://www.xs650.com/forum/showpost.php?p=269253&postcount=18
