Misfire after sitting a few months-not fixed...

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I said this before on the first page of this marathon so maybe you forgot, our bikes are old but new technology really can help. Why fart around drilling through jets etc. when ultrasonic cleaning is widely available? It's not voodoo, it works and it won't damage anything and if nothing changes you can eliminate the carbs as the problem.
 
Fart around? Drilling and cleaning. i have used your ultrasonic method. after 1/2 hour of "fizzing" the jet was still blocked
. These cleaners work on cavitation but if the blockage is "soft" varnish they dont work . Its like trying to grit blasting rubber..same result.

pev said:
I said this before on the first page of this marathon so maybe you forgot, our bikes are old but new technology really can help. Why fart around drilling through jets etc. when ultrasonic cleaning is widely available? It's not voodoo, it works and it won't damage anything and if nothing changes you can eliminate the carbs as the problem.
Click to expand...
 
I am reworking the ground connections now. I thought of running wire directly from battery before, but didn't after checking that voltage was over 12 volts with key on, but motor was not running. This is the first positve earth vehicle I have worked on, and I am a little intimidated by the electronics. I suppose its the same as negative earth, just the opposite, if that makes sense.
 
I'm left handed so makes good sense for me to keep straight but various non red earth returns that make my brain smoke. My Trixie came with altered loom so she's still half factory with old bullets and half custom color coded and tangled enough I can't tell what/where the mis colored wire connect to originals- so only testing each out put w/o wire manual guide me on her. Trixies key swithc only acts as on/off power to ignition but from part of loom so screwed up I figured our a way to get tail and head light on/off switch in head lamp shell and the hi/low beam working. Thank goodness no trun signlas on Triixie to figure out or would just order new loom to start from scatch to save labor and mistakes. Btw if ya ain't found out already about 1/3 of the factory loom is useless dead end red earths and unconnected Y's and loops going nowhere w/o the police features active. Wes's '71 wired similar with just an ignition toggle switch and same for lights but no signals clutter to mess with us.
 
Hobot, Thank you for the wiring info. I do have connectors going nowhere under the tank, some not being used since I switched to electronic ignition. Over the weekend I did look at my head and tail lamp wiring, and it looks pretty clean. Mine has turn signals. One side works well, the other is slow. I could see someone was in the headlight working on wiring as they are marked with tape and writing. Tri Spark instructions advised to make sure wiring was good in those areas.

A few years ago I changed the head steady and lost that ground. So, I made a new one which worked well. But, it doesn't look so good now, so I am redoing it. It could be the culprit. Hope to find out tonight.
 
Ok James we got about same handling issues on scabbed up wiring re-connecting to workias expected for a tessing intervals. Alas no different than other old or even modern issued craft, expect easier to get too on vintage. Almost always bad return thru plastic chrome mounts and stem stalk that screw with blinkers and many including my have resorted to our on red return thru the stem. I rejoiced getting Trixie Combat w/o signals. I do not know half of how Trixie is rewired where I can't see and learned to live with the mystery till forced too. Oh yeah try slapping banging or kicking the weak winker, worked great for me plenty of times...before riding off carefree as road vibes automatically assisted. Got me some leasure time so off to bash something else on Peel to perfection.
 
My next test will be running wire from negative battery post directly to Tri spark. Although voltage shows 12.6 while not running, thought I would just see if any different wired direct.

Tomorrow going here:
http://www.bsaocnc.org/Clubmans/Halfsheet.pdf

Like to get it running right for their Sunday ride.
 
I hot wired the ignition, by passing the switch, no difference in misfire. I have the carbs off now, I see no problem with them. I drilled out the plugs leading to the air valve adjustment, looks clean inside. Is the pilot jet an actual brass jet that hangs down into the bowl area? Or is it an almost invisible itty bitty thing screwed up into those threads? If it hangs down into the bowl area, it will certainly suck up fuel.

While at Rabers yesterday, one of the people who works there showed me an assortment of pilotjets, but wasn't sure what size I would need for my 850 Commando. They looked to me like they would screw in and hang down below the carb body, rather than go into it. Any thoughts? Thanks.
 
The pilot jets in all later concentrics are not replaceable.
All the passages and drillings need to be clean and clear.

You said earlier, it now starts and idles OK.
That means all is now good in that dept.....

Did you try at any time to tug on the individual throttle cables to each carb, to see if each carb individually will rev up the engine.
It had developed to sounding like the carbs were not well synched, or one wasn't throttling up at all.
That test would have told you IF that was the case, and more importantly which one.

I still think you need to try that, it will tell you lots.
I know, the solution will probably be that the taillight is loose (joking),
or the tires need pumping up, but you never know.
A compression test - to see that both cylinders are good - may be useful if this goes much further.

Ain't old bikes fun.....
 
Thank you, Rohan, for replying. I will try the cable pulling. I had planned to make sure the cables are synched when I put it back together. I saw a number of Nortons yesterday at the show in San Jose running one carb. Made me glad to have my Amals.
 
They work good, when you get all the bugs out.
Its just sometimes its hard to figure out where that durned bug is....

Interested to hear what you find.
Hopefully its not that loose taillight...
 
jamesp said:
I hot wired the ignition, by passing the switch, no difference in misfire. I have the carbs off now, I see no problem with them. I drilled out the plugs leading to the air valve adjustment, looks clean inside. Is the pilot jet an actual brass jet that hangs down into the bowl area? Or is it an almost invisible itty bitty thing screwed up into those threads? If it hangs down into the bowl area, it will certainly suck up fuel.

While at Rabers yesterday, one of the people who works there showed me an assortment of pilotjets, but wasn't sure what size I would need for my 850 Commando. They looked to me like they would screw in and hang down below the carb body, rather than go into it. Any thoughts? Thanks.
Click to expand...
The parts hanging from the carb bottom into the bowl area is the main jet (brass) which is screwed into the jet holder, (steel) and screwed into carb body from the bottom. A needle jet (brass) is screwed into the jet holder at it's threaded end before it enters the carb. Put a wrench on that steel jet holder and it will all become clear.

Ignore the little threaded hole at in the bottom of the carb, nothing is meant to be threaded into it. If you have drilled out the thin plugs opposite the air screw, then, with the air screws removed, you should be able to see that tiny .016" air jet, the one that we're all talking about that MUST be clear. By the way, if you were too rambunctious with the drill you'll be able see through the carb with no trouble because you have drilled through the pressed in pilot jet and have opened up a new can of worms.

Still as a couple of us have said, if your bike starts easily and idles nice the pilot/idle mix circuit is (or was) OK.
 
Biscuit said:
The parts hanging from the carb bottom into the bowl area is the main jet (brass) which is screwed into the jet holder, (steel) and screwed into carb body from the bottom. A needle jet (brass) is screwed into the jet holder at it's threaded end before it enters the carb. Put a wrench on that steel jet holder and it will all become clear.
Click to expand...

Aha, Good comment.
If the 'bits hanging down' haven't been apart yet and checked for cleanliness, then they need to be.
The needle and needle jet are what fuels the bike at medium revs,
and if they are gummed up or not clean, then this may be where your problems are.
 
...And also jamesp, what the gentleman at Rabars showed you a variety of were most likely main jets with lots of choices ranging from in the high 100's to the low 300's in size. Not your problem, unless as Rohan mentioned, plugged. Or, what you were showed were needle jets, of which there are for all practical purposes only three,,, #105, #106, (the one you should be running) and #107. Take the jet holder out and inspect.
 
"Ignore the little threaded hole at in the bottom of the carb, nothing is meant to be threaded into it."

Quote above is what I was concerned about. Norton shop manual shows that there is a small jet that goes into this hole. I assume that its buried in there? I couldn't see anything.

I understand about the main jets and their holder. My bike came stock with a 230, I have tried a 260 but it was too rich. My main jets are all clear. I pulled them out from bottom of carb. while on bike and checked them early on.

I have drilled out the pilot jet plug, it was clear. I threaded the holes and just need to get a plugs for them. I have all new gaskets and will put carbs back together soon. As I said earlier, I did not see anything wrong with carbs.

Next on my list is to check valves, but they were also ok before problem started.

Thank you for all your feedback. This problem has started me on a journey through this bike that has me checking everything. Its good, I can dig it.
 
another thing to look at is a possible broken valve spring. 4500 RPM is about it will float a valve with the inner spring broken.

jamesp said:
Tonight was first time I've had a chance to ride it. It starts easy,idles great, but starts misfiring above 4000 rpm, closer to 4500. Also ran uneven at part throttle. Danged.
Click to expand...
 
bill said:
another thing to look at is a possible broken valve spring. 4500 RPM is about it will float a valve with the inner spring broken.

Ok, I will look for that. Will it be easy to spot? Thanks.
Click to expand...
 
Ran fine last season, so extremely unlikely a valve spring broke from just sitting. You've been jumping down enough rabbit holes chasing this problem, leave this one alone.

Did this bike run really well last year, or just OK but better than now?

Look for PM
 
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