Before I reinstall the slides I run the idle screw down till there is just a sliver of light under the butterflys, point them at bright light, adjust till they match, that will get you REAL close if the engine is healthy.
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need help from a carb guru...
- Thread starter chopitdropit
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- carburetors how to
chopitdropit
XS650 Addict
I tried the popsicle stick method and they looked good...just didn't know how accurate that would be. I'll double check with your method tommorrrow Gary.
In the meantime, since I know that I have a major "rich" problem on the left carb and no parts anyway...I think I will also pull the floats and needles again, switch them and see if the problem moves to the right side carb. If it doesn't, I've eliminated a float/ needle issue as being the problem, right?
In the meantime, since I know that I have a major "rich" problem on the left carb and no parts anyway...I think I will also pull the floats and needles again, switch them and see if the problem moves to the right side carb. If it doesn't, I've eliminated a float/ needle issue as being the problem, right?
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Your mix screws should dial in very close to one another and near the factory spec. If one carb requires a setting way different than the other, that usually indicates a problem in that carb or with that cylinder. It doesn't necessarily have to be a carb problem, it could be ignition related. Is the plug cap and wire good? Switching them side to side is a fast and easy check. Are you sure your float is set correctly? These carbs can be very picky about that. How about the condition of the needle jet? If it's worn or been eaten away by gas residue, the carb will run rich.
The factory never gave a spec for the mix screw setting on the BS34s. They were set to meet pollution standards then capped over so you couldn't mess with them. They seem to run best at between 3 and 3 1/2 turns out. If you happen to get a set with the factory plugs still in place and remove them, you'll usually find the screws set somewhere around 2 3/4 turns out. But remember, this setting was to meet emissions standards, not for best running.
The factory never gave a spec for the mix screw setting on the BS34s. They were set to meet pollution standards then capped over so you couldn't mess with them. They seem to run best at between 3 and 3 1/2 turns out. If you happen to get a set with the factory plugs still in place and remove them, you'll usually find the screws set somewhere around 2 3/4 turns out. But remember, this setting was to meet emissions standards, not for best running.
chopitdropit
XS650 Addict
Good info 5twins. Thanks! I did find a cracked spark plug cap on the right side a few days ago and replaced it.
Having the hose barbs in the carb holders gives you an easy place to hook up the manometer. I use the homemade yard stick, clear plastic hose one. Very sensitive. Once the carbs are synced, hooking the two barbs together with a hose seems to help the bike run smoother.
chopitdropit
XS650 Addict
I wanted to post up and say thanks for all the help guys! Betwwen this forum and being willing to jump in to something I knew nothing about, I have learned a great deal about carbs. Here is an update on my carbs.
After replacing the boots and diaphrams, going through carbs several times, The bike now has no air leaks and idles normally...woohoo! (adjusting the valves helped tremendously also, the exhaust on both sides had 0 lash...now at .006 w/ intake at .003).
The last problem I have to resolve is, even though both carbs are set up identical now, the right carb seems to run great, plug looks good, but the left carb is fouling the plug, and is rich as an international banker (plug is black in short order). I was suspicious of the float needle and seat in this carb, so replaced with new one from Mikesxs.
Running condition is good low idle and good 1/2 to full throttle response, but missing like a seive at light throttle which is my main riding condition in town.
I still have to pull the pilots again and get a magifying glass for the #,s and I only have my fuel mix screws out 2 turns because of the rich left carb. (3 1/4 was stock on the 1982 so this trips me out).
My sync is just popsicle stick method...but doubt this is my problem anyway, but still will try gggGary's method next time carbs are off. (They have been off so many times, I can now take them off without having to remove or loosen ANYTHING else!!!)
I ran a compression check and both cylinders were about 100 psi (this seems low compared to most bikes??), but at least they are the same, eliminating this as my left carb problem.
I found a chart here before that showed what jets controlled what throttle with overlaps but can't find it now...anybody Know the link? Of course, any other comments and suggestions are welcomed and appreciated!
Almost there!!!
After replacing the boots and diaphrams, going through carbs several times, The bike now has no air leaks and idles normally...woohoo! (adjusting the valves helped tremendously also, the exhaust on both sides had 0 lash...now at .006 w/ intake at .003).
The last problem I have to resolve is, even though both carbs are set up identical now, the right carb seems to run great, plug looks good, but the left carb is fouling the plug, and is rich as an international banker (plug is black in short order). I was suspicious of the float needle and seat in this carb, so replaced with new one from Mikesxs.
Running condition is good low idle and good 1/2 to full throttle response, but missing like a seive at light throttle which is my main riding condition in town.
I still have to pull the pilots again and get a magifying glass for the #,s and I only have my fuel mix screws out 2 turns because of the rich left carb. (3 1/4 was stock on the 1982 so this trips me out).
My sync is just popsicle stick method...but doubt this is my problem anyway, but still will try gggGary's method next time carbs are off. (They have been off so many times, I can now take them off without having to remove or loosen ANYTHING else!!!)
I ran a compression check and both cylinders were about 100 psi (this seems low compared to most bikes??), but at least they are the same, eliminating this as my left carb problem.
I found a chart here before that showed what jets controlled what throttle with overlaps but can't find it now...anybody Know the link? Of course, any other comments and suggestions are welcomed and appreciated!
Almost there!!!
chopitdropit
XS650 Addict
i just read a thread where I should open throttle to full during compression test...plus I realized my tester had the glass collapsed right around the 100psi and up mark and may have been stuck...so have to redo the compression test. Saw where 150 would be optimim.
In the meantime..based on above post and what I have already done...still hoping someone will pop in with thoughts on why I'm having these fouling/rich issues with the left carb.
In the meantime..based on above post and what I have already done...still hoping someone will pop in with thoughts on why I'm having these fouling/rich issues with the left carb.
Yes, you should open the throttle wide open, some even prop the slides up. The book calls for 145 lbs as stock compression value. 150 is average, anything over 125 will run ok. Any less and the engine will lack power.
When I did the top end on my 75 the compression, on the engine stand, no carbs, kicking with kick start was 165 on both sides. After break in on a warm engine throttles held open was 155 each side.
The easier the air can enter the cylinder the higher the reading.
When I did the top end on my 75 the compression, on the engine stand, no carbs, kicking with kick start was 165 on both sides. After break in on a warm engine throttles held open was 155 each side.
The easier the air can enter the cylinder the higher the reading.
chopitdropit
XS650 Addict
Hey Leo! Yeah, that's why I know my compression test was jacked. I have plenty of power. 1/2 to full throttle this rig kicks arse. It's just below 1/3 throttle left side rich and fouling plugs. Rode awhile today and just shoved in a new plug about every hour or so of ride time
, because I was sick of working on it and had to get the wind in my face and some fog from thinking about it out of my brain
...I even packed extra tools and rechecked my valve adjustments under a shade tree on the side of the road. Just wrenchin and ridin.
Any new ideas on the left carb issue?
, because I was sick of working on it and had to get the wind in my face and some fog from thinking about it out of my brain...I even packed extra tools and rechecked my valve adjustments under a shade tree on the side of the road. Just wrenchin and ridin. Any new ideas on the left carb issue?
TeeCat
One-Mik Wonder
This is a good thread, guys. I'm learning a lot, as I have similar issue, though mine seem to be intermittent and idle/off idle primarily. So I'm thinking my bowls need dropped off and pilots cleaned again.
Question related to the original poster's: The three holes in the throat on the 38s... at what operating range are they active? Above off-idle? Are they transitional? At speed? I'm just looking for evidence (some of which I have found in this thread, thanks) to concentrate on the pilots.
chopit... sounds like you're getting there! Frustrating, isn't it??!!
Question related to the original poster's: The three holes in the throat on the 38s... at what operating range are they active? Above off-idle? Are they transitional? At speed? I'm just looking for evidence (some of which I have found in this thread, thanks) to concentrate on the pilots.
chopit... sounds like you're getting there! Frustrating, isn't it??!!
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The list is fairly long yet
An ignition issue
Oil fouling?
Have you done a clear plastic tube float level test? It is hard to do on some carbs but is definitive on float level / leaking float valve. With everything else you have done, and that the left runs good on higher throttle settings it has my high suspicion.
Compression / valve leak on the left.
An ignition issue
Oil fouling?
Have you done a clear plastic tube float level test? It is hard to do on some carbs but is definitive on float level / leaking float valve. With everything else you have done, and that the left runs good on higher throttle settings it has my high suspicion.
Compression / valve leak on the left.
The BS38's have a threaded, capped vacuum port near the front of the carb. I had to turn down a couple of adapters in my gauge kit to clear a nearby carb bracket but after that was done the port is easy to use.
chopitdropit
XS650 Addict
The list is fairly long yet...hmmm...lovely...haha!
Not oil foul..black sooty and dry plug.
Have not done clear tube test, just set floats to specs...I will do it. (deep down, I'm still thinking float issue also)
Compression / valve leak on the left.[/ geez, I hope not.
P.S. mine are bs34's
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chopitdropit
XS650 Addict
TeeCat...if you are talking about the 3 holes on the butterfly side...two are bypass for idle and one is your air mix also for idle. All pilot circuit. This might help
http://www.xs650.com/forum/showthread.php?t=43
scan down for cutaway diagrams.
There is also a chart that shows overlap ranges of jet/slide operation posted somewhere by inxs, but I can't find it right now.
If they are the foam float ones the tube test is so easy. You HAVE to do it.
Have you switched the plug wires from side to side and seen if the black plug follows? That will confirm or eliminate ignition as the problem. When you cleaned the carbs, did you remove, clean, and inspect the condition of the needle jet? They can get eaten away inside by gas varnish. That makes the metering hole bigger and the carb runs rich.
My buddy's bike ran rich and blackened plugs for the last few years. He swore up and down that he totally cleaned the carbs and replaced everything that needed it. I finally got a look inside his carbs earlier this summer. They were all fucked up, lol. He had MikesXS plastic floats installed in '80 brass float carbs but he used the brass float setting. And also, probably the root cause of his problem, his needle jets were dirty and all eaten away inside.
My buddy's bike ran rich and blackened plugs for the last few years. He swore up and down that he totally cleaned the carbs and replaced everything that needed it. I finally got a look inside his carbs earlier this summer. They were all fucked up, lol. He had MikesXS plastic floats installed in '80 brass float carbs but he used the brass float setting. And also, probably the root cause of his problem, his needle jets were dirty and all eaten away inside.
chopitdropit
XS650 Addict
Thanks 5twins...two more things to check on my list this saturday. I have factory electronic ignition and it's a single coil...if its turned out to be an ignition problem, what would I be looking for?
You're looking for a bad cap and/or plug wire. Unplug both spark plug wires and simply cross them over to the opposite plugs. If the black plug switches sides, you've most likely found the problem. The stock plug caps go bad sometimes. The resistance in them climbs and that chokes off the spark.
chopitdropit
XS650 Addict
OK guys...I switched plug wires from side to side and went on a test run....no ignition probs. I have the carb apart again and the needle valve looks good...did need a little cleaning since I didn't know I could get it out through the throat before.
I am going to set up for a clear plastic tube float level test, as after I got back from the run and pulled the pods I noticed a dry right throat and a gas film in the left....
First I am going to reset the float height. So here is my...maybe...last question (yeah..right!)
With the carb upside down the right side carbs float needle (which has no issues) goes in and the little rod on the end of it goes in also. So then I set my height.
The left goes in but then I have to push down on the floats and when I let go the little pin springs back up. This is the side I just put new needle and seat in.
So when I set height on this side is it with the little pin up, or do I lightly push on the bowl and bottom it out???
Truth is, It is apparent it is spring loaded and maybe the right side has lost its tension...but I don't want to fawk with the right side...it took long enough to get it set right to begin with.
I am going to set up for a clear plastic tube float level test, as after I got back from the run and pulled the pods I noticed a dry right throat and a gas film in the left....
First I am going to reset the float height. So here is my...maybe...last question (yeah..right!)
With the carb upside down the right side carbs float needle (which has no issues) goes in and the little rod on the end of it goes in also. So then I set my height.
The left goes in but then I have to push down on the floats and when I let go the little pin springs back up. This is the side I just put new needle and seat in.
So when I set height on this side is it with the little pin up, or do I lightly push on the bowl and bottom it out???
Truth is, It is apparent it is spring loaded and maybe the right side has lost its tension...but I don't want to fawk with the right side...it took long enough to get it set right to begin with.
Sundie
Jabroni
If there is no spring - it's set wrong. That's just a simple fact.
No spring = replace. This would cause an issue.
Just get a rebuild kit, they're cheap. Come with float pin, float pin seat, o-ring and bowl gasket.
