Author Topic: Lumpy when Cornering  (Read 302 times)

Offline DazRR

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Lumpy when Cornering
« on: 15.06. 2022 22:14 »
My A10 has a 389 monobloc, when taking right hand corners it sounds like one cylinder becomes more prominent almost sounding like a single,  left handers she sounds normal, Firstly I thought it was just an illusion as there seems to be no drop in power however I tried leaning her whilst stationary and when lent to the right it definitely becomes lumpy, I'm presuming this can only be fuel related, any ideas ?

57 A10RR

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Re: Lumpy when Cornering
« Reply #1 on: 15.06. 2022 22:20 »
Maybe just the way the noise echos off the road surface.

Leaning the bike over while stationary is not the same as cornering.

Offline DazRR

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Re: Lumpy when Cornering
« Reply #2 on: 15.06. 2022 23:29 »
Maybe just the way the noise echos off the road surface.

No its not,

Leaning the bike over while stationary is not the same as cornering.

No but it proved there is an issue as leaning to the left had no effect but to the right it runs lumpy

57 A10RR

Online BSA_54A10

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Re: Lumpy when Cornering
« Reply #3 on: 16.06. 2022 09:32 »
That is what the concentric carburettor was invented to cure .
Get some extended float bowls or don't lean so hard into corners
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Trevor

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Re: Lumpy when Cornering
« Reply #4 on: 16.06. 2022 10:30 »
Remember, when cornering gravity / centrifugal forces mean the effect on the carb is virtually as if the bike is upright. Only on combinations does cornering have a profound effect on carburetion.
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Online Triton Thrasher

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Re: Lumpy when Cornering
« Reply #5 on: 16.06. 2022 11:53 »
That is what the concentric carburettor was invented to cure .


The Concentric was invented to be narrow and cheap.

Offline Clive54bsa

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Re: Lumpy when Cornering
« Reply #6 on: 18.06. 2022 01:17 »
DazRR, try this experiment, when the bike is idling at say a traffic light or Stop sign, if you lean it to the left slightly does the idle speed up and if you lean it to the right does it slow down? This is a condition I have experienced on my Golden Flash with a Monobloc 376 fitted. I have a Monobloc 389 on my Super Rocket and it doesn't behave this way. I've told by old racers a lot wiser than me that this is called "Amalitis". I have tried many things to try to mitigate this problem, and the only way I was successful was to fit a Concentric carb. It doesn't look right as it's supposed to have a 276 carb. but it cured my idle issue. Good Luck


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Re: Lumpy when Cornering
« Reply #7 on: 18.06. 2022 10:00 »
Quote
DazRR, try this experiment, when the bike is idling at say a traffic light or Stop sign, if you lean it to the left slightly does the idle speed up and if you lean it to the right does it slow down? This is a condition I have experienced on my Golden Flash with a Monobloc 376 fitted.
I've no doubt it would but, as explained in an earlier post, that won't happen when riding unless you're going round a corner pulling a chair. As such, this won't occur during normal use, so I can't see how this could be an issue.
'49 B31, '49 M21, '53 DOT, '58 Flash, '62 Flash special, '00 Firestorm, Weslake sprint bike.

Offline Slymo

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Re: Lumpy when Cornering
« Reply #8 on: 20.06. 2022 05:11 »
I'd check the float level which you can do with a bit of clear pipe over the pilot jet with the covering cap removed then lifted up beside the float bowl cover. There is a nipple in the middle of the cover that the fuel level should align with. Also check the plugs as if leaning it makes it richer or leaner on one side its likely that they will be different colours.
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Offline DazRR

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Re: Lumpy when Cornering
« Reply #9 on: 24.06. 2022 10:50 »
Thank you all for your help and info, I've solved the problem now, I found the gasket was missing at the base of the jet block, It must have been seeping fuel from the float chamber when cornering to the right, there is no difference in tick over now when I lean the bike whilst stationary and she sounds normal when out on a run cornering.

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Re: Lumpy when Cornering
« Reply #10 on: 24.06. 2022 11:22 »
Nice one!
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