Runs well, plugs foul....

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I use tickle and choke to start my bike when cold. I also cut my fuel tap 1/4 mile from home when I put her to bed. But that just works for my bike.
 
Runs well, plugs foul....
Mwood7800 said:
Double check the timing.
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acadian said:
OP said he set timing via degree wheel, so I'm just assuming he's already verified the timing gauge marks are correct (or most likely off)
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Photo displays getting setup.
Timing good, thank you for the attention guys.

After I install new floats I am going out to the airfield and run some plug chops on a tank of 100 octane aviation fuel (no ethanol) with a hotter plug and needles in leanest setting. I can do this without getting into the main jets....
Should help get a better understanding of where it is and next step.
I’m still hoping it is just a straight forward float bowl adjustment at fault.
 
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Lineslinger said:
View attachment 9541




Photo displays getting setup.
Timing good, thank you for the attention guys.

After I install new floats I am going out to the airfield and run some plug chops on a tank of 100 octane aviation fuel (no ethanol) with a hotter plug and needles in leanest setting. I can do this without getting into the main jets....
Should help get a better understanding of where it is and next step.
I’m still hoping it is just a straight forward float bowl adjustment at fault.
Click to expand...

Great, when you set the degree wheel at 28 BTDC, where does the timing mark on the rotor land in relation to the gauge in the primary cover? In my case the primary gauge is 4 degrees off...
 
Lineslinger said:
A bit lengthy but please bear with me, just making info as complete and accurate as I can.

1974 850 Cmndo. The engine starts and runs well through full RPM range...until the plugs start to foul...within 30 miles.

I am running twin Amal 932's that I have overhauled. New slides, 3 position needles, main jets (standard 220's), floats and float needles. Synchronization between the two is good.


Thanks for reading.
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Well my 1974 850 Commando stock jets were 260 main jets and I have owned the bike since new, but with the work done to my motor I up the main jets to 270, in my workshop manual it said the same the M111s have 220 main jets so 220's aren't standard for the 74 850 Commando, but these days I am running PWK carbies but am thinking about going back to the Amal's.

Ashley
 
It seems you've done everything you should, all the logical things. Time to think about illogical things. I was once sold the wrong slides. Is the number on the bottom of the slide the same as the old ones? Could you have been sold richer slides?

Also, back to my previous comment about a small amount of oil burning turning the plugs black, is there any blue smoke? Just a hint of it when you give it a rev? Could be rings?
 
A good strobe shot on the ignition wouldn't hurt, either. Good way to check the advance curve.
 
Try running it without the air filter and see if it helps, there have been reports over the years of people having difficulty setting up the carbs with these filters.
 
acadian said:
Great, when you set the degree wheel at 28 BTDC, where does the timing mark on the rotor land in relation to the gauge in the primary cover? In my case the primary gauge is 4 degrees off...
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The inner primary reference gauge was off by less than 1 degree in relation to the rotor.
Hard to believe, maybe another comparison in order.
I used an electrical meter and a TDC reference indicator to locate my true TDC. Damn close if not dead on.
 
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pommie john said:
It seems you've done everything you should, all the logical things. Time to think about illogical things. I was once sold the wrong slides. Is the number on the bottom of the slide the same as the old ones? Could you have been sold richer slides?

Also, back to my previous comment about a small amount of oil burning turning the plugs black, is there any blue smoke? Just a hint of it when you give it a rev? Could be rings?
Click to expand...

I installed new slides during overhaul. Sizing matches.
No smoke. Head redone. Cylinders honed with new rings and properly seated.
It’s a mixture issue thus looking at your observation “illogical things” as where to go next if my little bit of testing doesn’t work out.
 
dave M said:
Try running it without the air filter and see if it helps, there have been reports over the years of people having difficulty setting up the carbs with these filters.
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Huh, the K&N is all about more air and I have not put any oil on it yet, too new.
Something to think about.
 
Lineslinger, I only mention this because it is such a quick thing to check and I recall that not all previous reported issues were related to too much oil in the filter.
 
You might want to do a side by side comparison of the slide cutaways or measure the slide cutaways. I’ve seen things mis-marked and incomplete manufacturing before.
 
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Runs well, plugs foul....
Runs well, plugs foul....
Runs well, plugs foul....
Measuring/comparing is a good thought which I did upon installing the new slides.

Thank you for the attention.
dave M said:
Lineslinger, I only mention this because it is such a quick thing to check and I recall that not all previous reported issues were related to too much oil in the filter.
Click to expand...
 
dave M said:
Lineslinger, I only mention this because it is such a quick thing to check and I recall that not all previous reported issues were related to too much oil in the filter.
Click to expand...

It’s a good idea.
When I first received it I blew out the filter from the inside with compressed air just to be sure too much oil was not impregnated in the filter medium. I over oiled a K&N dual quad filter once and this cleared it. The new Filter for the Norton was as as it should be.
 
Onder said:
What exhaust do you have installed?
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Post#10
you show only a muffler.
What is the exhaust system?
850 balance pipe? Carb tune is different than individual 750 style pipes. Air cleaner affect it too.

I run BP6ES in my MKIII. Same plugs for over 3 seasons. Runs like a top
 
Wish my carbs was that purty. That gremlin is fast running out of hideouts. There's something hiding in them. I don't know what or where, but I'm more than sure it's in them. Sorry for thinking out loud.
 
wow, this is a real problem to solve

I will take one more shot, maybe maybe the choke slides are not fully retracted and are letting in enough of a richer mixture to cause the fouling?

question: it is possible the choke is left on too long after cold start?
 
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