Author Topic: one cylinder (running lean)  (Read 1831 times)

Offline lowbrowbsa

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one cylinder (running lean)
« on: 26.10. 2011 16:43 »
why ist that one pot can run lean on a single carb head if so how do you fix
 ???? ???? *dunno*

Online bsa-bill

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Re: one cylinder (running lean)
« Reply #1 on: 26.10. 2011 17:03 »
Quote
why ist that one pot can run leen
well the most common reason given here and elsewhere is simply that one pot draws more mixture in than the other, usual answer is to try a biased washer between the carb and the manifold to direct more fuel mixture to the side that's lean.
However that raises an interesting question, although the mixture drawn into either potmight be different in volume it should be the same in regard to the petrol/air ratio so maybe the term weak or lean in this instance is inaccurate, if indeed the mixture petrol/ air ratio is different then possible causes could be worn valve guides or air being sucked into one side of the carb gasket.

Anyway lowbrow thanks for allowing me to forward an alternative view, lets see what the wiser heads make of it
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline wardleybob

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Re: one cylinder (running lean)
« Reply #2 on: 30.10. 2012 12:55 »
I would have a look at your mag slip ring try to ballance the timeing

Offline duTch

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Re: one cylinder (running lean)
« Reply #3 on: 31.10. 2012 12:40 »
 Can't remember if I posted on this before, but maybe last year when I started cleaning up my head, I noticed that under the valve heads, in the inlet ports, around the area of the downstream end of the valve guides, had differing profiles, a bit the same in exhaust side.
 I already had a profile gauge, but bought a Dremel and did some 'sculpting/whittling/dental work', to make things even, carved out about 4mm from one area- am yet to know if I made a difference(detrimental).
    Thing is it never ran uneven, actually ran priddy sweet, except for the maggie/condenser, by which time I had repaired, the rest of bike had gone faecal, and haven't really ridden it for a long time, but when I saw those uneven profiles, wondered if it was a contributor to the dreaded 'bias' that it seems can't quite be otherwise defined..?
 Open to comment, and hopefully soon (before the end of the year) will have a road test.
  Cheers duTch
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline a10gf

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Re: one cylinder (running lean)
« Reply #4 on: 31.10. 2012 14:28 »
Some opinions, check L\R ignition for any differences in timing, check valves (closing properly, guides), then move on to investigating carb bias. Many topics on the matter, example: try searching for bias gasket

(& edited topic title to better reflect subject)

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Offline The pirate

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Re: one cylinder (running lean)
« Reply #5 on: 31.10. 2012 14:45 »
Hi there, I have been playing with A10's for countless years, mine and other riders, and have heard just about every argument for bias etc I dont know what is correct or not - but what I do know is the induction bias gasget between the carb and the head not only keeps the carby cool it cures sooting of one plug and evens out the color.

I use a very old gadget called a "colortune" (that you stick in the spark plug hole to show how the mixture in the cylinder is firing), and it shows up when the bias gasget is the wrong way around and shows correct when it is on the right way. Cant tell you why but it works.
The Pirate

Online stu.andrews

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Re: one cylinder (running lean)
« Reply #6 on: 01.11. 2012 10:24 »
Can really recommend the Colourtune which seems to be still available. Look on ebay if necessary. Good for checking the combustion in each cylinder, setting up worn carbs, checking for leaky valves etc, & an ideal addition to any toolbox.
2010 Yamaha TDM 900-Touring
2012 Triumph Bonneville SE-Fun


Online bsa-bill

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Re: one cylinder (running lean)
« Reply #7 on: 01.11. 2012 11:28 »
Looks like I'll be needing to use my colourtune, shifted the RGF from the garage (temp storage) to the shed, about three or four minutes running and one side ex pipes is now purple/blue the otherside not so bad.
Prefer the look of my Flash pipes a nice golden colour.

Done a few miles on the RGF without the pipes blueing, wonder if it could be the fuel gone off a bit, but then again more on one side.
Another strange thing, this is the bike with electronic ignition and voltage control, battery keeps going down and thought faulty VCU however I get a drain from the battery through the ignition on/off switch of .35 volt this with the switch off (thinking faulty switch must check when time allows).

Sorry to hijack your mail  lowbrowbsa  but somebody might suggest something that helps us both
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Triton Thrasher

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Re: one cylinder (running lean)
« Reply #8 on: 01.11. 2012 17:41 »
I would have a look at your mag slip ring try to ballance the timeing

Cam ring.