'73 850 won't start-need advice!

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Blue850

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My 850 has been a one or two kick starter and ran great until it sat for two months this past fall. Spark looked really weak so I replaced 2 new coils and condensers and checked all wiring as best I could. Super hot spark now and battery is only one year old. Guessed it might be clogged passages in the carbs so I removed them both and did what I hoped would be a thorough cleaning, carb cleaner, compressed air and super fine wire in the pilot/mixture passages. It has started twice over numerous hours of fiddling and kicking but once it does, that's it, won't start again. Valves are set correctly, compression is fine. New spark plugs, no ethanol gas. I'm at my wits end and it's too nice to turn into a living room conversation piece! Any advice would be greatly appreciated!! Thanks! Steve
 
Bypass your kill switch and see if that makes an improvement.
 
What those guys said. It's EXTREMELY unlikely ...to the point of being almost impossible...that coils/condensers/spark plugs went bad while sitting for two months. ;) In addition to the suggestions, bad gas IS possible.
 
Also try bypassing ign switch if original. Those can go bad giving flakey connections.

Did you confirm fuel is getting to carbs from tank?
What about the pick up passages bottom of float bowl all the way through body base to pilot jets? That passage hard to clear as two ninety degree bends.
 
If you are running points, clean up the points with a points file.
If they are too badly burnt, replace them.
One of the keys to a sweet running, points fired Norton is to keep the points cleaned and dressed.
 
elefantrider said:
Probably fuel/carb related. They don't need a powerful spark to start/run.
Click to expand...

They do, however, need spark. My kill switch went intermittent and left me stranded long ago until I finally put a jumper wire across it. It'd run and suddenly stop.
 
What I meant to say is it will run with a weak spark also. Make sure your plug gap is within the manual's recommendation, preferably on the tighter side of that range, if old points/wiring etc.
 
Test, don’t guess.

Put some gas directly into the plug holes. Runs for a second? Ok, keep looking for fuel delivery problems...
 
Are you using chokes?
If the bike is stored a damp environment that green current killer verdigris might well be growing in the ignition switch, fuse holder and connections.
 
Don't discount the bad fuel observation...too many times I have finally figured out, after trying everything else, it was moisture in the fuel, and it doesn't take but a tiny bit.
 
The kill switch on the handlebar RH control cluster is not well sealed from the elements. It is also vulnerable to any bleeding or spilt brake fluid. During a ride I had tagged the kill switch and the bike went dead and stayed dead. There was no time to figure it out road side so it was a transport back.
 
Bypass it under the tank. If you're still using points, unplug the white/blue (ballast resistor) from the white/yellow (kill switch) and plug it into one of the white (switched power) sockets.
 
concours said:
Test, don’t guess.

Put some gas directly into the plug holes. Runs for a second? Ok, keep looking for fuel delivery problems...
Click to expand...

concours and I always are on the same wavelength for this kind of thing, but with a slight deviation. He always says, "take the plugs out and squirt some fuel in and reinstall", and I always say, "pull the air filter off, twist the throttle open and give a squirt with a squirt bottle of fuel down each intake plenum...

In both cases, all you are doing is a test to see if you are going to follow the "fuel delivery" possibility OR the "faulty ignition" possibility. If it tries to run and then dies with either of our fuel tests, it's more than likely a fuel delivery issue!
 
Finally! After checking the ground, kill switch, and re-checking all the other stuff, it starts! I had already tried the gas in the spark plug holes and replaced the gas in the tank and carbs, all to no avail. When the spark was so weak, I added new coils and condensers since the originals were 46 years old, figured it wouldn't hurt. Still nothing when I'd kick it over. So today, after researching how plugs can have a bright spark laying on the head and not fire under compression, I installed a second set of NGK B7ES plugs. Like magic, one kick and it roared to life! If this rain would let up a bit I'd go for a ride. Thanks so much for all the ideas and input! Steve
 
o0norton0o said:
concours and I always are on the same wavelength for this kind of thing, but with a slight deviation. He always says, "take the plugs out and squirt some fuel in and reinstall", and I always say, "pull the air filter off, twist the throttle open and give a squirt with a squirt bottle of fuel down each intake plenum...

In both cases, all you are doing is a test to see if you are going to follow the "fuel delivery" possibility OR the "faulty ignition" possibility. If it tries to run and then dies with either of our fuel tests, it's more than likely a fuel delivery issue!
Click to expand...


The difference is, the ham can is lengthy to take off/put on. Not everyone realizes the FLAME ARRESTER built into most every OEM air filter. I’d feel terrible if someone burned their bike (and possibly garage) to the ground, based on my recommendation. That’s why I’ve said to gas it in the plug holes.
I’ve shot fuel/ether into the carbs of hundreds of engines over the years, to test for viability. But, I’ve also had them go on fire. And cranked car engines to suck the flame out, etc. (All in the heat of battle) This was all to get an engine running in minutes, not weeks. The same tests are valid though.

So... for bikes:
Fuel tank OFF
temp fuel supply.
Outside.
BIG fire extinguisher nearby
 
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