Author Topic: cuts out when hot  (Read 1331 times)

Offline oval57

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cuts out when hot
« on: 17.01. 2016 20:15 »
I have a 52 A10 that has had a restro and only done 300 miles. Everything has been rebuilt in the engine, mag overhauled, new everything but has ben fitted with a concentric carby. Problem is it starts easy, idles sweet, accelerates well everything nice. Once it gets hot when you come back through the gears at an intersection everything is fine until you nearly stop and then it cuts out. If you are quick enough a little throttle will keep it running. It starts again easy as but will cut out if you let it drop back to idle. A couple of revs for a second or two and it will idle. Plugs are burning nice, valves at 10 thou, as far as I know timing is right, carby has a 3 cut away,needle on third notch, tried second no different. Got me buggered

Started with a basket case, now got 3 BSAs and a shed full of bits.....mmmm feel another BSA coming on...whoops two more followed me home...

Online trevinoz

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Re: cuts out when hot
« Reply #1 on: 17.01. 2016 20:19 »
Did you set the idle mixture when it was hot?

Online muskrat

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Re: cuts out when hot
« Reply #2 on: 18.01. 2016 00:55 »
That's the first thing I thought of too Trevor.
No use doing any carb adjustments till it's fully warmed up. That may take 10 miles or more just to get the oil warm.
Getting it all sweet when first started (or the next 5 minutes) will be way too rich when hot.
Back the pilot screw out 1/4 to 1/2 turn.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Offline oval57

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Re: cuts out when hot
« Reply #3 on: 18.01. 2016 05:39 »
Will give that a whirl tonight and see how I go.

Started with a basket case, now got 3 BSAs and a shed full of bits.....mmmm feel another BSA coming on...whoops two more followed me home...

Offline Rocket Racer

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Re: cuts out when hot
« Reply #4 on: 18.01. 2016 08:32 »
as a baseline I'm assuming the carb has a tufnol washer to prevent overheating and the mag armature has sufficient end float to spin freely and not bind when hot. Neither the mag nor carb like getting too hot.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline oval57

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Re: cuts out when hot
« Reply #5 on: 18.01. 2016 12:20 »
How do I check magnet end float?  I went for quite a long ride and then reset the carby, it was better but still stalls as you back off at an intersection

Started with a basket case, now got 3 BSAs and a shed full of bits.....mmmm feel another BSA coming on...whoops two more followed me home...

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Re: cuts out when hot
« Reply #6 on: 18.01. 2016 18:23 »
What condition is the carb? Slide/body wear, flange warped, tufnol heat shield, fuel height correct. Then there's timing. Manual or auto advance? Same both sides? Plug colour?
Rings not bed in yet (should be after 300 miles), when backing off oil is sucked up past the rings and foul the plugs. A few twists of the wrist clears them.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Rocket Racer

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Re: cuts out when hot
« Reply #7 on: 18.01. 2016 20:23 »
How do I check magnet end float?  I went for quite a long ride and then reset the carby, it was better but still stalls as you back off at an intersection

That does sound more like a mixture problem than magneto
 I have come across mag's that were assembled incorrectly shimmed so they start binding the bearings, overheat and fade out.
Often a full rebuild where lots of things are changed so a time a number of things can conspire.

What carb are you running?
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline oval57

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Re: cuts out when hot
« Reply #8 on: 19.01. 2016 01:08 »
They fitted a new Wassel concentric, reckon I will rebuilt an Amal I have and change it over I think. Just a few clues keep steering me to fuel but you can get set in your thoughts. There appears to be plenty of spark as it kicks over first or second kick when it stalls. Problem is it doesn't do it every time

Started with a basket case, now got 3 BSAs and a shed full of bits.....mmmm feel another BSA coming on...whoops two more followed me home...

Offline Rocket Racer

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Re: cuts out when hot
« Reply #9 on: 19.01. 2016 01:59 »
what size concentric? 626, 627, 928, 930 ?
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline oval57

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Re: cuts out when hot
« Reply #10 on: 19.01. 2016 09:42 »
Wassel 928 carb 170 main jet 106 needle pilot bush 3 throttle valve.. On 3rd notch down from top...Amal is a 276GG 170 main jet 6/4 throttle valve .108 needle how important is the spacer everyone refers to ?
Checked timing all good points at 10 not 12 thou starting to wear me down🤔

Started with a basket case, now got 3 BSAs and a shed full of bits.....mmmm feel another BSA coming on...whoops two more followed me home...

Offline Rocket Racer

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Re: cuts out when hot
« Reply #11 on: 19.01. 2016 10:04 »
tufnol washers insulate the carb from the worst of heat transfer from the head, you still get some from the studs, but far less.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline chaterlea25

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Re: cuts out when hot
« Reply #12 on: 19.01. 2016 14:33 »
Hi,
Wassel jet sizes cannot be relied on  *angry*
There may be some "crap" loose in the pilot passageways ??

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Rocket Racer

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Re: cuts out when hot
« Reply #13 on: 19.01. 2016 20:46 »
But the bike is running nicely when cold and warmed up, just playing up when hot?
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline oval57

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Re: cuts out when hot
« Reply #14 on: 21.01. 2016 09:17 »
Reset points to 12 thou but found the auto advance was fairly tight, got it moving better and it seems to have sorted out the stall problem. Fingers crossed. Went for a long ride then reset car by. Hopefully I have sorted it .....thanks for your input

Started with a basket case, now got 3 BSAs and a shed full of bits.....mmmm feel another BSA coming on...whoops two more followed me home...