FH650 Restarting problem

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john.mitchell
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FH650 Restarting problem

Postby john.mitchell » Fri Mar 25, 2011 2:55 pm

I have a strange problem with my rebuilt FH. It starts when cold 1st kick with a tickle and on choke. It ticks over exceptionally well and rides perfectly. If I stop it when hot, it restarts easily.
However, if I stop it and leave it for 10 minutes it refuses to start again until the engine has cooled down. It has the same big blue spark on both plugs hot, warm or cold.
Neither the carburettor or magneto seem particularly hot to the touch.

Any ideas?
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adrie.degraaff
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Re: FH650 Restarting problem

Postby adrie.degraaff » Fri Mar 25, 2011 3:28 pm

Hi John,
try a heath blocker between the head and carb.

Adrie.
Last edited by adrie.degraaff on Sun Mar 27, 2011 5:50 pm, edited 1 time in total.

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charles.bulloch
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Re: FH650 Restarting problem

Postby charles.bulloch » Fri Mar 25, 2011 6:14 pm

I had similar problems with my VH. I kept swapping between a reconditioned and an old magneto with no difference. I tried Champion plugs which seemed slightly better. What fixed it, though, was a reconditioned magneto. The machine started first kick after the winter lay off.

I have been advised my an old motorcycle dealer not to use a resistor plug cap, as it can burn out the magneto.

I hope this is of use to you.

Charlie

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Postby admin » Fri Mar 25, 2011 6:32 pm

If it was the mag, then wouldn't there be bugger all spark ?? John reckons it's sparking strongly, even when it's not starting.
When my VB wouldn't hot start, and it was the magneto, it had a really, really rubbish spark...
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charles.bulloch
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Re: FH650 Restarting problem

Postby charles.bulloch » Sat Mar 26, 2011 6:31 pm

When I replaced my own magneto, the spark still looked OK on the old one, but no better on the reconditioned one. I even made a spark tester. The new magneto did not spark over a bigger gap, about 4-5mm. I have heard that the condenser is the culprit. Its properties change with temperature. Or something. My VH would start first kick when cold, but could need dozens of kicks after filling up with petrol.

A right nuisance and very embarrassing.

By the way my Guzzi needs to whirr on the button a fair bit before it starts from cold and the Ariel handles better. I hope you fix your problem soon.

Charlie

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Postby tony.barnett » Sun Mar 27, 2011 1:49 pm

admin wrote:If it was the mag, then wouldn't there be bugger all spark ?? John reckons it's sparking strongly, even when it's not starting.
When my VB wouldn't hot start, and it was the magneto, it had a really, really rubbish spark...


A weak mag will spark happily outside the cylinder but put it under working conditions and the spark will be feeble.

John - get your mag tested. Might be it needs an overhaul.
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Re: FH650 Restarting problem

Postby Wali.Badger.Taylor » Sun Mar 27, 2011 11:06 pm

If you do not have an insulating spacer twixt head and carb add one , it can do no harm but I am with the majority and put it down to your mag. Get Tony Cooper to fill it with sparks.


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