My Norton runs badly...help!

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J

JD

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Hey all-
I have a small issue that I have seen some threads on earlier, but cant seem to find them. I was riding my Mk3 on a 20 mile jaunt around my town, all was right with the world for about 19 of those miles. A bit of history on the bike, I just finished the resto on it about a month ago and have been riding the legs off of it ever since. It has been performing flawlessly. Anyway, about mile 19 the bike fell on its face leaving a stop light. It was popping and sputtering like it was running on 1 cylinder. At the next stop light all I could think is oh, crap! These bikes are heavy! Pushing this home wouldnt be fun. But I got to the next light, the idle came to a nice rest at about a grand like it always does. I gave it a rev or 2 and it sounded beautiful. When the light turned green, though it was a different story. Same thing--flat on its face. I made it home thank goodness. I got it home and did all the usual checks. I checked plugs, checked spark, timing, wiring at the points--yes no Boyer on this cruise missile. I pulled carb bowls and jets and blew compressed air through, although they had been rebuilt and tuned. Slides fit as they should with no play. I have played with the carbs and have ridden it, swapped plugs for a known good set, etc. The result is still the same. the drivability doesnt change. Any ideas? Thanks for your help.
JD
 
JD said:
Hey all-
I have a small issue that I have seen some threads on earlier, but cant seem to find them. I was riding my Mk3 on a 20 mile jaunt around my town, all was right with the world for about 19 of those miles. A bit of history on the bike, I just finished the resto on it about a month ago and have been riding the legs off of it ever since. It has been performing flawlessly. Anyway, about mile 19 the bike fell on its face leaving a stop light. It was popping and sputtering like it was running on 1 cylinder. At the next stop light all I could think is oh, crap! These bikes are heavy! Pushing this home wouldnt be fun. But I got to the next light, the idle came to a nice rest at about a grand like it always does. I gave it a rev or 2 and it sounded beautiful. When the light turned green, though it was a different story. Same thing--flat on its face. I made it home thank goodness. I got it home and did all the usual checks. I checked plugs, checked spark, timing, wiring at the points--yes no Boyer on this cruise missile. I pulled carb bowls and jets and blew compressed air through, although they had been rebuilt and tuned. Slides fit as they should with no play. I have played with the carbs and have ridden it, swapped plugs for a known good set, etc. The result is still the same. the drivability doesnt change. Any ideas? Thanks for your help.
JD
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Bad gas? Rust come loose from inside your tank plugging the fuel lines? Plugged up fuel lines? Shouldn't be an issue if you just restored it though. Did you replace fuel lines? When I bought my Commando, it had been doing a lot of sitting around and the fuel lines were pretty gunked up. Had the same kind of experiences you describe.
 
Fuel lines are the clear original style and new. I pulled the fuel lines and cleaned what little there was in the screens. No rust from the tank. The bike is basically brand new. Some head work was rumored to have been done prior to my ownership and then the bike sat in an old, old Honda repair shop for several years. Its got to be something so easy that has been glanced over. Thanks for the help.
 
Is the spark a strong blue spark at kickover or is it thin and whitish?
If it is the latter then look to the ignition side of things.
You could have a problematic coil, condensor or
points, especially if they are Lucas pattern points made by Daichi.

I had a new set of these fail on my Vincent 430 miles from home. The Vincent has been modded with a Norton Commando point setup. If you have the Daichi or other pattern points in there, they are guaranteed to fail. I think the supplier I found recently still has a few sets of 10CA NOS Lucas points for the post 73 Commando if you need some. The original Lucas points are a very high quality item, they have been known to last up to 70,000 miles with a couple of filings (diamond file is best)

The 650SS that I just got had not run properly since it was totally restored in 1999. In researching the history of the bike, I learned that initially the complaint was lack of power, but over time it started to misfire at higher RPM. The previous owner was non-mechanical (he won the bike in a raffle) so he just stopped riding it after a few years. By this time it was pretty much as you have described your bike, it would rev up quite nicely in neutral, idle OK, but under load it sounded like WW3. That was how the bike ran when I first got it.
Eventually I traced the problem to the key ignition switch. As soon as I bypassed that all of the banging and popping disappeared and the bike took off like a rocket. So in addition to the other possible ignition problems mentioned, try bypassing the ignition key, it just might be the problem.
 
Just a thought - but it sounds like a low battery to me. The fact it happened at a stoplight suggests the battery ran down from idiling at the light - when you get the revs up there is more current.

I had a similar problem - with a low battery

Give the bat a good charge and see.

Glad to hear you are out riding! 8)
 
Agree on the low battery. Also check alternator for output.
Bike may be running on battery only.
Also, resistor plug wires with resistor plugs don't work well with low output ignition.
 
Thanks all for the help. I have not been shocked at all by the oddities that can sometimes plague these machines. It's love hate sometimes. To answer a few questions, though, the bike runs perfectly at idle. When the throttle is opened (in neutral) the bike revs fine and settles right back down. There is a big, fat blue spark coming from each lead when starting, idling and with the throttle open. Stock carbs and ignition system throughout. I will check battery voltage, though it may not be an issue. Being a MK3, I gauge the ability of the starter motor on the condition of the battery. The bike fires right up with the push of a button. I will for sure check the state of the charging system. I will also bypass the ignition system and give that a shot. I'll be sure and let you all know what worked. It's part of the fun old bikes. Who wants a predictable Japanese bike anyway??!!
 
Nortonruns badly

Just a thought, check that the fuel taps are not partially blocked by dissolving rubber seals.This could begin to starve the fuel flow,I had a similar problem on my '74 850. At idle all was well, but under acceleration the gas flow was diminished causing a lean mixture. New gas taps with good seals cured the problem -- full fuel flow on both taps. Good luck. Ride safely. James.
 
Well, after a few mis-spent hours with my British mistress, I think James' suggestion of the fuel taps being clogged may have been the issue. I gave the bike a bath and finished up a few tiny details that needed to be done, even if I never got the bike running right again. Just as a last ditch effort, I put the bike on the lift and removed the right fuel line from the tap. I stuck my funnel inside my 5 gal gas can to catch the spill when I opened the tap. Well, when I opened the tap there was a pathetic little trickle coming out. It takes the little light bulb in my head a bit of time to brighten some times. Long story short, I pulled both fuel taps and could hardly blow a stream of air through each. BRAND SPANKING NEW TAPS!! The "expensive" ones. I disassembled both taps and made the needed repairs and tested the flow again. 100% different. It's well after 11 pm here so I havent ridden the bike yet, but would expect it to be better. Thanks again and thanks in advance for the help next time. I'm riding it to work in the morning. Wish me luck!
JD
 
Long story short. The main jet holder in the right carb was unscrewing itself while I was riding it. Dont I feel like an arse because I had the bowls off to inspect the debris or lack there of inside. The clogged fuel taps did help a bit, but I guess my problems were compounded by a couple of issues. Just got back from my 20 mile loop and all is right with the Norton again.
Thanks all.
JD
 
Main point...problem solved. :D

Main jet happened to me too, bout five years ago, me and the son on his Suzuki went to Verdun to think about how humans could possibly be so destructive to each other and somewhere in France the Commando started to act funny. Stopped for a bit and looked the bike over and found nothing. Started every time, so although she was running a bit funny, continued on north, did a loop around Luxembourg on the Autobahn, with every truck trying to drive up the butt of me and my son because his bike was "governed" due to his age and it would only do a bit over 45 mph on the highway. Trucks would come up behind me, (who did the father thing and drove behind the son)... three or four feet behind me, and blow their horns at us. Butt holes to say the least. Anyway...long story short, two days after the bike started to run funny, we get home after the thousand miles at 45 mph or less, and I finally get a look at the the Commando in my own garage and not some farmers road in the countryside. Removed the bowls...and the jet was lying in the bottom of one. Stinker had still started...even that morning before I worked on it. LOL

Goes to show...
 
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