Author Topic: Hot starting problem  (Read 7719 times)

Offline bullrush

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Hot starting problem
« on: June 22, 2015, 06:31:45 PM »
My 1957 Thunderbird starts great when cold but when the engine is hot it just does not want to know. I tried a plug change but no difference. There is a good spark and compression.
« Last Edit: June 22, 2015, 06:35:09 PM by bullrush »

Offline mini-me

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Re: Hot starting problem
« Reply #1 on: June 22, 2015, 07:01:05 PM »
check tappets, are they tight?

or condenser failing

Offline mark2

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Re: Hot starting problem
« Reply #2 on: June 22, 2015, 07:50:18 PM »
coil ?

Offline JFerg

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Re: Hot starting problem
« Reply #3 on: June 22, 2015, 11:28:09 PM »
Magneto.  An open circuit in the HT winding build a small track of carbon.  This has a low resistance when cold, but a high resistance when hot.  Great spark and easy starting when cold, but weak when hot.

Offline R

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Re: Hot starting problem
« Reply #4 on: June 23, 2015, 05:03:02 AM »
Great spark and easy starting when cold, but weak when hot.

Exactly the same symptoms/behaviour from a failing condensor in the magneto also.

These neat little new fangled brightspark condensors that sit in the points housing (with original condensor disconnected) seem to be the answer to many an ailing magneto. Unless the wiring itself really is kaput, ot course, a much less common problem it seems though.

P.S. NOS condensors are to be avoided like the plague, they can degrade sitting on the shelf.

Offline mini-me

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Re: Hot starting problem
« Reply #5 on: June 23, 2015, 08:24:50 AM »
1957 6T  should be coil ignition.

Offline R

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Re: Hot starting problem
« Reply #6 on: June 23, 2015, 09:21:56 AM »
Duff coil or condensor then.

Covered all the possibilities now.
Hopefully....

Offline mark2

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Re: Hot starting problem
« Reply #7 on: June 23, 2015, 06:26:53 PM »
is the bike fitted with Amal or SU carb ? has it the insulation block fitted

Offline R

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Re: Hot starting problem
« Reply #8 on: June 25, 2015, 05:45:59 AM »
Could even be limited fuel flow out of the fuel tap(s), or a blocked breather in the fuel tank cap.
Any pause, and a slightly limited fuel flow catches up ?

Offline iansoady

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Re: Hot starting problem
« Reply #9 on: June 25, 2015, 11:20:06 AM »
Always worth fitting a new condensor / capacitor IMO as they're hard to test and very cheap.
Ian
1952 Norton ES2
1986 Honda XBR500
1958-ish Tre-Greeves

Offline 33d6

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Re: Hot starting problem
« Reply #10 on: June 27, 2015, 01:36:39 PM »
You were right first time R, it's failing ignition. It's a no-brainer. Given it's a '57 T'bird the chances are very high at least parts of the ignition are still original and very tired. Not unless the owner can afford a professional restoration anyway.
Cheers,

Offline mini-me

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Re: Hot starting problem
« Reply #11 on: June 28, 2015, 09:05:25 AM »
Do people just questions and bugger off? what was the result?

Offline murdo

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Re: Hot starting problem
« Reply #12 on: June 28, 2015, 10:47:31 PM »
It appears so.

Offline cardan

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Re: Hot starting problem
« Reply #13 on: June 29, 2015, 03:38:05 AM »

Stay calm - he's probably out in the shed studying the ignition on the Thunderbird. In a busy world it's sometimes hard to reply to every post.

Leon