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Post by kassrocket on Nov 29, 2011 1:22:08 GMT -5
Gday.. Since I changed my damaged tank to a brand newie from Mikes XS i seem to be having backfiring problem.. It seems to be also idling quite low and does stall at times depending on its mood.. The backfiring occurs consistently when i am deccelerating and when i am at idle at the traffic lights it pudders and sometimes stalls... I checked the vacuum tubes and they seem to be fitted fine.. Also the petcocks are on there ok it seems.. Never had this problem before so i am dumbfounded.. Any ideas would be great?
Cheers..
Josh
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Post by richard on Nov 29, 2011 4:53:12 GMT -5
What year is your bike again?
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Post by kassrocket on Nov 29, 2011 7:30:40 GMT -5
79 Special
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Post by grizld1 on Dec 2, 2011 9:37:24 GMT -5
OK, let's take this one step at a time. Set your petcocks on "Prime," go for a ride, and tell me what happens.
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Post by XS Rod on Dec 2, 2011 15:19:06 GMT -5
Griz... sounds like you been here before...
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Post by grizld1 on Dec 2, 2011 21:33:04 GMT -5
It could be a host of things, Rod. Instead of trying to list every possibility and barrage guys with troubleshooting drills, it's sometimes better to go one step at a time and hit the easy stuff first. I'll be surprised if the first check I suggested uncovers the grief.
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Post by kassrocket on Dec 3, 2011 23:17:46 GMT -5
Ok.. will try Griz.. Sounds good ruling these things out one by one.. Cheers.. Will get back to you..
Josh
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Post by kassrocket on Dec 6, 2011 23:23:48 GMT -5
Griz.. I turned both petcocks onto prime and rode it and it still did the same thing.. idled considerably low and stalled on me once at traffic lights.. They are not extremely loud backfires but they are consistent on deccelaration.. Kinda medium level backfires.
Josh
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Post by grizld1 on Dec 8, 2011 0:52:48 GMT -5
Sorry for the slow reply; been fighting computer glitches. Going to "Prime" eliminated failure of the petcock diaphragms as a cause of trouble, as the "Prime setting bypasses the vacuum-actuated valve and lets fuel flow even with the valve closed. So--your problem isn't in the tank or petcocks. As a next step, go for a ride, and with the engine running, spray a short burst of carb cleaner or WD40 at both ends of the carb boots (at several points) and the ends of the throttle shafts--both inside ends and outside ends. After each short, localized burst of spray, wait 3 seconds or so for the engine to respond. A change up or down in idle speed means you've hit a vacuum leak. Let me know the result.
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Post by XS Rod on Dec 9, 2011 10:07:55 GMT -5
Going after the source of it running so lean... cool cool... I'm just hung up on the tank being the only variable entered... Josh you sure no other changes were made... didn't touch the carbs or ignition bro? Did you find where it might be sucking air? Un-metered air that is
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Post by grizld1 on Dec 10, 2011 10:08:35 GMT -5
Maybe a lean condition, Rod, maybe not. If this step is negative for vac leaks we'll move on to other things.
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Post by kassrocket on Dec 22, 2011 17:52:43 GMT -5
Yeah i checked it out and it seems after spraying quick spurts of wd-40 into the carb boots their is no change to idle.. Hmmmm.. Head scratch.. Perhaps it could be something related to the ignition.. Think i have to start from the beginning.. I am quite sure i did not touch anything when replacing the tank but i could be mistaken.. I have one of those Boyer Branson ignitions on it so perhaps it may be something to do with that.. Although I am positively no bike expert so i could be totally wrong???
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Post by grizld1 on Dec 23, 2011 9:54:06 GMT -5
Right, Josh; the Boyer system needs a healthy power supply for its electronic advance function as it should, so be sure the box is getting full 12V power and its ground wire has a good, clean connection to the frame or the engine. At this point I'd advise you also to inspect cam chain tension, valve lash, and ignition timing, in that order.
If there's no joy after those steps, check to be sure that there are no leaks between head and headpipes or between headpipes and mufflers. If you don't find issues there, let me know. The next step will be to get into the carbies, but we'd be putting the cart before the horse to do that before the maintenance adjustments above are confirmed.
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pamcopete
Full Member
'78/E, '81/H, '82 XJ550, '74 CB750, '81 CB750, '73 CB450
Posts: 167
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Post by pamcopete on Dec 23, 2011 15:27:10 GMT -5
kassrocket,
Try putting the old tank back on.
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pamcopete
Full Member
'78/E, '81/H, '82 XJ550, '74 CB750, '81 CB750, '73 CB450
Posts: 167
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Post by pamcopete on Dec 23, 2011 21:23:25 GMT -5
Right, Josh; the Boyer system needs a healthy power supply for its electronic advance function as it should, so be sure the box is getting full 12V power and its ground wire has a good, clean connection to the frame or the engine. Here is a video of the PAMCO Ignition working with a 6 volt lantern battery: The PAMCO worked this way even when the lantern battery went down to 5 Volts.
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