Author Topic: low float level symptoms  (Read 351 times)

Offline paulbaker1954

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low float level symptoms
« on: July 10, 2019, 08:11:43 AM »
Hi,
My bike has been not quite right since last rebuild for head gasket. I think it may be down to float levels but just wondered what the symptoms pf low float levels are.

My issue is pulling away from standstill I have to ramp up the revs or she tries to stall. Hill starts are even more of a challenge requiring me to gun it whilst slipping the clutch. I am confident pilots are clear as they are new and I also checked recently all the pilot air channels but I think float levels on 3 and 4 may be a bit low.
If you think there's light at the end of the tunnel it's usually another train !!

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Offline Erny

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Re: low float level symptoms
« Reply #1 on: July 10, 2019, 08:45:11 AM »
Paul, not sure I understand your issue, isn't it rather too rich mix on low rpm symptom? The same I'm facing?

When you try to engage choke that should make mix richer (at least partially) it helps of make it worse?
If it helps, your mix is too lean, if it is worse, it is too rich... I'm not expert but this is my exprience

In my case I have clearly too rich mix and still did not fixed that (you know my thread well :) )

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Offline paulbaker1954

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Re: low float level symptoms
« Reply #2 on: July 10, 2019, 08:54:15 AM »
Paul, not sure I understand your issue, isn't it rather too rich mix on low rpm symptom? The same I'm facing?

When you try to engage choke that should make mix richer (at least partially) it helps of make it worse?
If it helps, your mix is too lean, if it is worse, it is too rich... I'm not expert but this is my exprience

In my case I have clearly too rich mix and still did not fixed that (you know my thread well :) )

That may well be the case but  I just was asking what the symptoms of low float levels are that's all
If you think there's light at the end of the tunnel it's usually another train !!

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Online K2-K6

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Re: low float level symptoms
« Reply #3 on: July 10, 2019, 09:24:16 AM »
Lower float level should make it run leaner,  but it's a very, very fine effect and probably heard more at tickover than any real feel in response.  That's if it's in error by a small amount.  Within a couple of millimetres of each other or aim point I think you'd be hard pushed to detect the difference. 

It should easily be out weighed by any adjustments in idle screws as far as engine response is concerned.

It's worth verifying your idle circuits to ascertain if they are all functioning well (I know you've got new jets) as just one out kilter can give you the affect described if that cylinder doesn't fire cleanly.  Revving more just brings you more onto main jets and kind of points to idles as cause of problem.

If you warm motor and let it idle,  then just wind each idle screw both in and out in isolation it will confirm with cylinder response if you've got a fully clear idle circuit. The other three should remain at their normal running setting while you do this.  Your'e just looking for a linear response as you go through the screw range for each carb. It'll soon tell you if you've not got normal response.

If they all check out as even response,  then try settings of all idle screws out a 1/4 and ride it,  then all in a1/4 (both from your initial set point)  to see how it feels in use.

Offline paulbaker1954

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Re: low float level symptoms
« Reply #4 on: July 10, 2019, 09:54:46 AM »
Thanks K2-K6 thats very helpful.

Its also odd as since the rebuild I am getting an odd afterfire (popping in exhausts rather than a  true backfire) in cyls 1 and 2 that happens only every minute or so (ie not on every firing stroke) which goes away when I wind the idle screws out a bit.

Not sure
If you think there's light at the end of the tunnel it's usually another train !!

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Offline Rob62

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Re: low float level symptoms
« Reply #5 on: July 10, 2019, 01:19:28 PM »
HAVE YOU CHECKED FOR AIR LEAKS ON THE INLET SIDE..? ALSO CHECK THE COMPRESSION, CHECK THE IGNITION TIMING/POINTS GAP AND REPLACE THE PLUGS, CHECK THE AIR FILTER ISN'T BLOCKED. IF YOU DO ALL THAT AND STILL HAVE AN ISSUE YOU CAN START TO GO THROUGH THE CARBURETOR SETTINGS.

Offline paulbaker1954

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Re: low float level symptoms
« Reply #6 on: July 10, 2019, 01:22:27 PM »
HAVE YOU CHECKED FOR AIR LEAKS ON THE INLET SIDE..? ALSO CHECK THE COMPRESSION, CHECK THE IGNITION TIMING/POINTS GAP AND REPLACE THE PLUGS, CHECK THE AIR FILTER ISN'T BLOCKED. IF YOU DO ALL THAT AND STILL HAVE AN ISSUE YOU CAN START TO GO THROUGH THE CARBURETOR SETTINGS.

Done all of the above !!!
If you think there's light at the end of the tunnel it's usually another train !!

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Offline Rob62

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Re: low float level symptoms
« Reply #7 on: July 10, 2019, 01:26:28 PM »
I FORGOT TO MENTION TAPPET CLEARANCES.... BUT I GUESS YOU HAVE CHECKED THOSE ALSO. IN WHICH CASE THE CARBS BECOME THE PRIME SUSPECT. GOOD LUCK WITH IT.

Offline taysidedragon

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Re: low float level symptoms
« Reply #8 on: July 10, 2019, 02:27:18 PM »
I FORGOT TO MENTION TAPPET CLEARANCES.... BUT I GUESS YOU HAVE CHECKED THOSE ALSO. IN WHICH CASE THE CARBS BECOME THE PRIME SUSPECT. GOOD LUCK WITH IT.


All good advice, but why are you shouting!? 😊
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Offline Rob62

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Re: low float level symptoms
« Reply #9 on: July 10, 2019, 08:22:49 PM »
Haha... i was at work on my pc with caps lock on.... wasn’t shouting, honest.... 😄

Online K2-K6

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Re: low float level symptoms
« Reply #10 on: July 11, 2019, 07:08:09 AM »
Thanks K2-K6 thats very helpful.

Its also odd as since the rebuild I am getting an odd afterfire (popping in exhausts rather than a  true backfire) in cyls 1 and 2 that happens only every minute or so (ie not on every firing stroke) which goes away when I wind the idle screws out a bit.

Not sure

Usually your first suspect is air leak on the exhaust side of combustion chamber that causes any popping in down pipe / silencer.  Or drop out from firing cylinder cleanly so you get occasional unburnt mixture going out of cylinder.

Just a thought about uneven running,  and your initial problem of pulling away.  How confident are you of HT leads? Have you tried running it in the dark and looking for escaped sparks around the leads?

Offline taysidedragon

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Re: low float level symptoms
« Reply #11 on: July 11, 2019, 02:07:14 PM »
Haha... i was at work on my pc with caps lock on.... wasn’t shouting, honest.... 😄

Pardon? 😉
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Offline paulbaker1954

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Re: low float level symptoms
« Reply #12 on: July 12, 2019, 07:22:58 AM »
Thanks K2-K6 thats very helpful.

Usually your first suspect is air leak on the exhaust side of combustion chamber that causes any popping in down pipe / silencer.  Or drop out from firing cylinder cleanly so you get occasional unburnt mixture going out of cylinder.

Just a thought about uneven running,  and your initial problem of pulling away.  How confident are you of HT leads? Have you tried running it in the dark and looking for escaped sparks around the leads?

Could you explain what you mean by drop out from firing cylinder cleanly so you get occasional unburnt mixture going out of cylinder.
« Last Edit: July 12, 2019, 07:29:21 AM by paulbaker1954 »
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Re: low float level symptoms
« Reply #13 on: July 12, 2019, 09:56:16 AM »
By drop out,  I mean a non fire for one or more cycles of that cylinder.

To get a backfire of any size in the exhaust pipe you have to have some proportion of fuel left unburnt.  Depending how rich carbs are set up that can vary,  but add a little oxygen from an exhaust leak to it, making it more volatile,  and you get that characteristic pop.  That can be normal with just the exhaust leak as a fault,  without that the rich mixture can just pass right through and give you a petrol heavy smell at exit without popping.

Your pulling away cleanly problem though suggests you've got at least one cylinder not firing cleanly while running at lower levels of carb range. This would also have the potential to give those exhaust backfire results.

So linking the two trait together suggests you've got a no fire result some of the time on one of the cylinders while on idle circuit.

The question is,  what is causing that? 

The check of HT leads may show you some leakage which can do this as it can give sporadic sparks. 

The other is of course carbs,  hence the question of what response you get by turning each screw individually to see if you are getting a linear response from each carb idle circuit in isolation. 

Offline paulbaker1954

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Re: low float level symptoms
« Reply #14 on: July 12, 2019, 10:57:58 PM »
By drop out,  I mean a non fire for one or more cycles of that cylinder.

To get a backfire of any size in the exhaust pipe you have to have some proportion of fuel left unburnt.  Depending how rich carbs are set up that can vary,  but add a little oxygen from an exhaust leak to it, making it more volatile,  and you get that characteristic pop.  That can be normal with just the exhaust leak as a fault,  without that the rich mixture can just pass right through and give you a petrol heavy smell at exit without popping.

Your pulling away cleanly problem though suggests you've got at least one cylinder not firing cleanly while running at lower levels of carb range. This would also have the potential to give those exhaust backfire results.

So linking the two trait together suggests you've got a no fire result some of the time on one of the cylinders while on idle circuit.

The question is,  what is causing that? 

The check of HT leads may show you some leakage which can do this as it can give sporadic sparks. 

The other is of course carbs,  hence the question of what response you get by turning each screw individually to see if you are getting a linear response from each carb idle circuit in isolation.

Thanks that’s great input, I have managed to get rid of the backfire by adjusting the idle screws, HT leads are pretty much brand new as they were all replaced last year when I fitted the full Boyer kit so am still suspecting an idle circuit problem. That said I did a full ultrasonic clean of the carbs last year and all the idle circuits were fine then.

It’s a lot better now having adjusted the idle screws and have chucked some redex in the tank so think will just run it a while and see if things settle down
If you think there's light at the end of the tunnel it's usually another train !!

2016 Yamaha MT09 Tracer
1971 Honda CB500 Four K0