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Balancing Carbs

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geoffnorfolk
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Balancing Carbs

Post by geoffnorfolk on Mon 05 Sep 2016, 8:49 pm

Strange one this!  Thought I'd balance the carbs whilst I had the tank off....... I've a set of really old Carbtune with mercury columns. Well the columns move ok but there was a difference in height but when I moved the adjusting screw, all that happened was the revs went up or down depending which way I turned the screw. The vacuum reading hardly changed. ~The more I loosened the adjuster, the higher the revs went. If I tightened the screw, the revs went down.  In the end, I just ended up screwing it back to roughly the same setting it was at...... seems to idle ok.  Any ideas what I might be doing wrong?!!   Many thanks
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ashcroc
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Re: Balancing Carbs

Post by ashcroc on Mon 05 Sep 2016, 9:02 pm

Could the pipes leading to the gauges have perished?
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geoffnorfolk
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Re: Balancing Carbs

Post by geoffnorfolk on Tue 06 Sep 2016, 8:04 am

ashcroc wrote:Could the pipes leading to the gauges have perished?

Everything looked ok........ perhaps I missed something then. They are 38 years old though so maybe the fault is there.  Seemed a bit odd that the revs kept climbing the more I loosened the screw.... thought they might go up a little and then start going down again...... the highest rev point being when they're almost right?
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alanp
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Re: Balancing Carbs

Post by alanp on Wed 07 Sep 2016, 2:55 pm

I just wonder if you were turning the correct screw and not getting confused with the tickover adjuster? I only mention this 'cos I've done that myself Embarassed
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eternally_troubled
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Re: Balancing Carbs

Post by eternally_troubled on Wed 07 Sep 2016, 5:23 pm

alanp wrote:I just wonder if you were turning the correct screw and not getting confused with the tickover adjuster? I only mention this 'cos I've done that myself :oops:

I was going to ask this too! :)

Anyway, twisting the carb sync screw can make the revs go up an down but on my new (spring loaded) carbtune it also makes the vacuum reading change as well.

My other though was that the rubber bits betweent the carbs and the engine have perished and are letting air in which is screwing up the reading.... however I would have thought if this was happening you would have worse probelms!
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geoffnorfolk
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Re: Balancing Carbs

Post by geoffnorfolk on Wed 07 Sep 2016, 6:47 pm

it was definitely the balancing screw...... the one you access from above the carbs. The idling screw was the yellow one which I found incredibly difficult to access!  I'm beginning to think there was something amiss with the gauges....... they are VERY old!...... however there's not much that can go wrong with them really. The carb rubbers seemed ok...... a bit hard but ok..... and the bike seems to idle quite nicely so perhaps I shouldn't have even bothered to check the balancing. I'm amazed how Mr Honda managed to design the carbs/airfilter with such tight tolerances to get them all on and off.... you'd think they could have given it all a bit more room....... still.... I'm getting better at getting those carbs on and off now lol.
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ceejay
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Re: Balancing Carbs

Post by ceejay on Wed 07 Sep 2016, 7:18 pm

I bought some cheapo gauges for about 20-25 quid. I guess I'll never know how accurate they are but judging by the way my bike runs they seem to be good enough and playing with the adjustment screw will have the effect you'd expect it to on the gauges.

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geoffnorfolk
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Re: Balancing Carbs

Post by geoffnorfolk on Wed 07 Sep 2016, 7:50 pm

What make are they........ looks great value at that price. I paid £25 for mine in 1978! Mine have these mercury columns and you can do 4 cylinder bikes on it as well. Used to work pretty well though I suspect now that the columns that the mercury goes up/down in might be blocked somehow. When I bought them, they just posted the mercury through the post.... no health and safety regs in those days!
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alanp
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Re: Balancing Carbs

Post by alanp on Wed 07 Sep 2016, 7:51 pm

Whoa, that bike is clean under the tank. Mine looks like its been covered in a mixture of oil and cow pats! Very Happy
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ANDYC
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Re: Balancing Carbs

Post by ANDYC on Wed 07 Sep 2016, 8:06 pm

Take the plug out of the larger diameter tube at the back of the guages. Remember to relace it though or you'll lose all the mercury which is nigh on impossible to get these days.
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ceejay
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Re: Balancing Carbs

Post by ceejay on Wed 07 Sep 2016, 8:13 pm

They say BikeTEK on them but are probably just generic ones that are branded under different names. I just found them here for 32... I bought them a few years back, maybe they've gone up since or maybe you can find somewhere selling them cheaper. You can also get the 4 cylinder/gauge ones but they are nearer 50 quid.

If you are really feeling creative I'm pretty sure I remember a few youtube guides out there on how to make your own!

Whoa, that bike is clean under the tank. Mine looks like its been covered in a mixture of oil and cow pats!

It's a pretty low mileage bike, I've certainly never been scrubbing away under there!
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eternally_troubled
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Re: Balancing Carbs

Post by eternally_troubled on Thu 08 Sep 2016, 5:29 pm

ceejay wrote:
Whoa, that bike is clean under the tank. Mine looks like its been covered in a mixture of oil and cow pats!

It's a pretty low mileage bike, I've certainly never been scrubbing away under there!

Mine looks awful under the tank too! (so you are not the only one)

You can make a u-tube manometer with clear tubing, water and colouring which will measure the pressure between two places.... but you do need a bit of wood to mount the manometer.

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geoffnorfolk
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Re: Balancing Carbs

Post by geoffnorfolk on Sun 11 Sep 2016, 5:08 pm

Well I decided to leave the carbs as the engine ticks over nicely!  Anyway, replacement carbs are all fitted though something not quite right. Idles nicely and accelerates ok if done fairly gently. If I open the throttle quickly, the engine stutters badly and "holds back"  At higher speeds it also doesn't feel quite right and down on power.  If I'm ambling along at say about 40-50, runs fine... higher speeds its holding back. Guess I'll have to take the carbs off again............. every time I do this, I get quicker and quicker which is a bonus!!!  Is there anything in particular that is likely to be the problem? I would guess the main jets would be the first thing to check?  Many thanks

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