goatman123 Posted September 20, 2011 Share #1 Posted September 20, 2011 I am trying to do a carb sync on my 93 that I am trying to bring back from the dead. I am using a Carbtune, and can't get a reading on it. I assume that is from lack of vacuum. I can't find any vacuum leaks by spraying carb cleaner around the carb boots, and the carb diaphragms look good to me. The bike only has 18,700 miles on it, so I wouldn't think the valve train would be out of adjustment. I can get the bike to start and run using the choke, and eventually it will idle without the choke, but if you give it throttle, it will die. With the choke on, it will rev up to 5-6k easily without giving it any throttle. I did find out today that number 4 cylinder is not firing, but I didn't think that would make the Carbtune not move. I get spark at #4, but loosened the carb drain screw, and nothing came out. Carbs will have to come off again, I already cleaned them once and they looked good except the idle jet was gummed shut. Obviously this bike sat for most of its life with only 18,700 miles on it, and I'm sure that's where all of my problems are coming from, but it sure looks nice, so I want to get it going. It has a woodgrain dash that appears OEM, I had not seen one of those before. Thanks for any help. Link to comment Share on other sites More sharing options...
MiCarl Posted September 20, 2011 Share #2 Posted September 20, 2011 It's amazing how much the vacuum will drop with just one cylinder out. Gotta get them all firing before you can sync it. Link to comment Share on other sites More sharing options...
Condor Posted September 20, 2011 Share #3 Posted September 20, 2011 Have you checked your diaphragms yet?? And adjusted the idle jet screws?? Link to comment Share on other sites More sharing options...
Marcarl Posted September 20, 2011 Share #4 Posted September 20, 2011 You'll need to have the choke open to get proper vacuum reading. Also check to make sure that the chokes themselves are in the open position, although you may have moved the lever back to off, the choke plungers may not have made it all the way back to open. Link to comment Share on other sites More sharing options...
SilvrT Posted September 20, 2011 Share #5 Posted September 20, 2011 Dumb question ... have you got the carbtune restrictors at the correct end? (closest to the carbs) Link to comment Share on other sites More sharing options...
Steveroge Posted September 20, 2011 Share #6 Posted September 20, 2011 You might check the compression, if no compression no vacuum. Link to comment Share on other sites More sharing options...
goatman123 Posted September 20, 2011 Author Share #7 Posted September 20, 2011 Thanks for replies. Diaphragms look good. Choke is operating correctly. Carbtune is hooked up properly. I have not checked compression, need to go to Harbor Freight and get a tester. What about the #4 cylinder not firing, would that cause no reading on the Carbtune? Maybe that is the whole issue? Link to comment Share on other sites More sharing options...
utadventure Posted September 20, 2011 Share #8 Posted September 20, 2011 In past threads there has been discussion about making sure the vacuum ports on the carbs aren't plugged from sitting. Also, I think it was Condor, help a member and mentioned making sure all of the sync screws were backed out so that the reading weren't effected, as well as setting the mix screws to a base setting. Help me out here Jack.... do I remember your advise correctly? Dave Link to comment Share on other sites More sharing options...
JoeKanuck Posted September 20, 2011 Share #9 Posted September 20, 2011 You can do a quick check for vacuum just by using your finger...or tongue. If you prefer your finger, just wet it and place it over the end of the vacuum port. Your finger should 'stick' to the port. Or...if you have especially insensitive fingers, get a piece of hose, (clean), which fits snugly over the vacuum port, get the bike running and close off the end of the hose with your tongue...don't worry...it won't peel the skin off of your tongue. At least it is possible for you to know if there is any vacuum at all at any of the ports. If yes, then it has something to do with the carbtune. Link to comment Share on other sites More sharing options...
Abbe Posted September 21, 2011 Share #10 Posted September 21, 2011 beware of backing screws on the right side to much, it will affect carb 2 and make the syncing quite a weird experiance... If stuff has been changed to much, pull the airbox and use a thin metal string and check the butterflies for similarity first. Carb 2 should be able to close with the use of the idle screw. If not, sync screw C on the right side is back out too far... Link to comment Share on other sites More sharing options...
Condor Posted September 21, 2011 Share #11 Posted September 21, 2011 beware of backing screws on the right side to much, it will affect carb 2 and make the syncing quite a weird experiance... If stuff has been changed to much, pull the airbox and use a thin metal string and check the butterflies for similarity first. Carb 2 should be able to close with the use of the idle screw. If not, sync screw C on the right side is back out too far... Agree'd. Don't back them off until they fall out, but do back them off a few turns. IF a PO has tried to set the idle using the #4 sync screw the whole sync will be screwed up and the carbs will be next to impossible to resync. You really don't need to get into the venturies. Just back off all the synch screws and start from scratch..... Link to comment Share on other sites More sharing options...
MiCarl Posted September 21, 2011 Share #12 Posted September 21, 2011 What about the #4 cylinder not firing, would that cause no reading on the Carbtune? Maybe that is the whole issue? Already answered in post # 2 Link to comment Share on other sites More sharing options...
goatman123 Posted September 24, 2011 Author Share #13 Posted September 24, 2011 Well I got the #4 cylinder running, and low and behold, the Carbtune showed some action, but only on #3 cylinder. I adjusted the sync screws from there(they were waay out of wack) and got it running pretty smooth and balanced. I still need to replace the rusty spark plugs and the questionable air filter, but progress is being made! Thanks for the help. Link to comment Share on other sites More sharing options...
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