Misfire on primary side.

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Quick Update: While thoroughly cleaning the carbs I discovered that the internals were a complete mismatch. Different cutaway on throttle valves, different main jets, different needles etc. Im kind of amazed the bike was running as well as it was before I started having issues. I also found a broken electrical connection from one of the coils that leads back to the positive side of the battery. Also noticed significant gunk clogging petcock filters from fiber glass tank. I ordered new guts for the carbs. Corrected the broken spade connector and am looking at steel gas tanks. Looks like the reproductions from Taiwan ($475) are popular with CNW and Old britts. Haso anyone had any experience with one of these prepainted steel tanks on ebay from India ($325)? Seems like a deal so must be a catch. Thanks
 
Update: Turns out the carbs were totally mismatched. Different spray tubes, needles, main jet, pilot jets etc. After much investigation I learned that I have a 72 combat not a 73. One carb was set up for the combat motor the other was not. Lesson - check your VIN not your Title. Anyway I rebuilt the carbs to match and fitted a new emgo tank. Tuned the carbs per bushman and the bike ran well for the test ride. I fitted a k&n air filter and now the bike doesn't want to start. It will fire but won't run. Should I open the throttle valves more to compensate for the air filter? Any suggestions appreciated.
 
Mine has done this a couple of times last summer on the right side cylinder. Still not sure what the cause is. Seems like the pilot jet is the most likely, but I have pulled the glass tank and was using a steel tank toward the end of the summer. Time will tell I guess but I am leaning to the pilot jet.
Could be electrical as well I guess. Hope not,
 
Before jumping the gun on your carbs or electrical... Basic tune up procedure is to always check your intake/exhaust valve lash first. After you have verified those to specs do a compression check on each cylinder (with the throttle wide open mind you). If either of those are off it can throw everything out of whack.

Only then would I recommend moving on towards other things...
 
Well the first thing I would do is take the K 7 N off and put whatever you had on it when it ran well back on just to see if that is in deed the issue. However I doubt the K & N could make such a difference that it wouldn't start. Good luck, Let us know the outcome please.
 
Update: I determined that there was an issue with the carburetorsame. The bike would run so long as I kept tickling the carbs. I believe there was a small amount of junk in the new emgo tank that gunked things up. I should have flushed the tank. I cleaned the carbs and pilot circuit and I'm back in business.
 
tomspro said:
djsktr said:
I also noticed that the spray tubes are not identical in my amal 932s. Rhe PO replaced the drive side carb. It has a half circle spray tube. The timing side carb has a full circle spray tube. Could this have an impact at idle?
Click to expand...

Perhaps the PO was trying to 'solve' a problem with a band-aid instead of surgery to correct underlying issue?
Click to expand...

I heard that when I had plug-fouling problems after I resurrected the SS clone. Turned out to be float levels were too high.
 
First try a leakdown test to identify engine condition and what might need attention. By this time your original idea of a Mikuni sounds good. It also eliminates a lot of variables.

Unrelated...I once had a fiberglass Norton tank bought at a real bargain that I was going to use for test rides. After careful cleaning I took off down the road. About 3 miles later I noticed that the slides were slow to return so I came back home. Seems the lining material was bleeding into the gas and coating the slides making them sticky. Learn something new every day.
 
Issue with starting resolved. Not sure what it was but probably idle air circuit. Replaced throttle and choke cables while I had the tank and carbs off. New emgo tank working well. Just need body work and paint. Any suggestions for body and paint services? Not quite sure how to post picture here but I will work on it.
 
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