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Carb sync troubles, different, and I searched...

  • Thread starter Thread starter MatBirch
  • Start date Start date
M

MatBirch

Guest
I'm sure it's been gone over before, and I apologize, but among all the threads available, I can't find specifics on this.
I'm having a buggar of a time getting these things to do anything but go "back and forth". As soon as I get one moving the right direction, it won't stop. Just keeps going right past the other. At times it feels like I haven't even turned the screw, just began to put pressure on it. But if the oil in the tube in question changes direction, it won't stop traveling until I make another adjustment. For several hours now, I've been wasting gas in a constant state of adjustment! The idle is also all over the map. It will change by 300-600 rpm with even the slightest touch of the screws, especially on #2. It will also change on it's own at times which will of course throw the levels off even more!

For reference- I'm using a homebuilt manometer with 90 wt oil/atf in it. I made threaded adapters out of .035 welding tips.
Carbs are cleaned, dipped, new o rings, new boot o-rings, valves adjusted, been over and over the maintenance stuff, and it should be spot on.

Please help!
 
MatBirch said:
I'm sure it's been gone over before, and I apologize, but among all the threads available, I can't find specifics on this.
I'm having a buggar of a time getting these things to do anything but go "back and forth". As soon as I get one moving the right direction, it won't stop. Just keeps going right past the other. At times it feels like I haven't even turned the screw, just began to put pressure on it. But if the oil in the tube in question changes direction, it won't stop traveling until I make another adjustment. For several hours now, I've been wasting gas in a constant state of adjustment! The idle is also all over the map. It will change by 300-600 rpm with even the slightest touch of the screws, especially on #2. It will also change on it's own at times which will of course throw the levels off even more!

For reference- I'm using a homebuilt manometer with 90 wt oil/atf in it. I made threaded adapters out of .035 welding tips.
Carbs are cleaned, dipped, new o rings, new boot o-rings, valves adjusted, been over and over the maintenance stuff, and it should be spot on.

Please help!
Click to expand...

There is your problem.
 
Hi, this is my first post since joining the forum. Many thanks to you all for an excellent source of info. Just for the record I have recently bought a '79 GS 850 as a general run around based on the fond memories I have of the one I owned 20 odd years ago.
I also made a manometer and found it really easy to balance my carbs, I'd stripped and cleaned them and set them up on the bench with a drill a bit as a gauge. I have used transmission fluid for the oil, I fitted the plastic pipe in a double figure of eight configuration to a board so I have 6 ft. of pipe filled with oil before the longer tails go to the carbs. This double figure of eight is about 18" high and the intention was to add a little more resistance than a straight U would give to slow down the movement of the oil.
The carb connectors I made are drilled 2.5 mm. In use I found the same as you, touch the adjusting screw and the tick over will drop drastically from the slide being pushed down by the screwdriver. Move the screw driver away and it goes back up again to normal. From many years of adjusting push rod tappets I used the method learnt for adjusting the carbs. Slacken the lock nut the bare minimum, to unscrew the adjusting bolt slightly, allow the screwdriver to move a fraction with the lock nut as it starts to loosen. Then hold the screw driver in the barely moved position as the lock nut is re-tightened, with tappets now re-check the clearance, with the carbs, move the tools away from the adjuster and check the reading.
To screw in the adjusting screw, as soon as the lock nut has loosened a fraction of a turn, put pressure on the screw driver to tighten the adjuster (the lock nut should still be a bit too tight to allow the screw to turn) and tighten the lock nut. The adjusting screw will turn a fraction as the lock nut tightens. Then same again, move the tools away to allow the tick over to be unaffected.
I've always found that adjusting the screw to the correct position before tightening the lock nut, the action of tightening the lock nut will alter the setting, slack in the threads etc.
None of my carbs needed more than a mere fraction of a turn to get them balanced, although the oil sucked up one sided on every one so they needed adjusting. I was amazed just how much smoother the bike runs in all throttle positions with just this fraction of adjustment, and it ticks over like a sewing machine.
Never shy away from home made tools and equipment, sometimes they need a little re-thinking/tinkering, but get them right and they can often be better than shop bought ones.
Colin
 
Thanks guys-
I have obviously no experience doing this, so I'm limited to the internet as my source knowledge. I know everyone has their own opinions, but I've read many, many times of successes with this type of manometer. And... As many negatives against gauges... For gauges, etc. I have read recommendations that straight ATF or similar is too light and will react too quickly. That's why I went with the 90 wt, and just enough ATF in it to darken it up a bit.

I kept at it for another hour or two this afternoon. I did find one old post recommending to completely remove the the throttle linkage and get it out of the way. Doing this almost eliminated the erratic idle. For some reason, it also seemed to help things balance?? The liquid bounced more than before, but the four tubes came together much easier. I stumbled upon the technique similar to what Artful Bodger describes, and by using more locknut, and less screwdriver, got them pretty close. I couldn't get the cool look like the photo with the two outsides just a hair higher than the insides, but they're all pretty close, and it runs well.

After all I've been thru on this bike, I'm just gonna stand pat, and let it be ridden for the remainder of the season. :cool:
 
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