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misfire.

Submitted by peter_denham on Wed, 22/06/2016
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Commando

Bad misfire pops on over run .Clean carbs /Good mixture any suggestions gratefully received apart from buy a BSA from my brother.

Submitted by martin_freeman on Wed, 22/06/2016

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Sounds like you have a leak on your exhaust, so check tightness of all joins, I have found original silencer clamps not up to job;try some of thes, but measure silencer carefully for OD

http://www.ebay.co.uk/itm/MIKALOR-W2-Stainless-Supra-Heavy-Duty-Exhaust-Pipe-Clip-Hydraulic-Hose-Clamp-/271326260811?var=570217368578&hash=item3f2c4e2e4b:m:m_9MZJyXp3KuvXH7oK3SnVw

If you have exhaust with balance pipe they never seem to fit without leaking; mine improved when warmed up with the gas, but I don't mind the burnt chrome!

regards martin

Submitted by peter_denham on Wed, 22/06/2016

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Previously Martin Freeman wrote:

Sounds like you have a leak on your exhaust, so check tightness of all joins, I have found original silencer clamps not up to job;try some of thes, but measure silencer carefully for OD

http://www.ebay.co.uk/itm/MIKALOR-W2-Stainless-Supra-Heavy-Duty-Exhaust-Pipe-Clip-Hydraulic-Hose-Clamp-/271326260811?var=570217368578&hash=item3f2c4e2e4b:m:m_9MZJyXp3KuvXH7oK3SnVw

If you have exhaust with balance pipe they never seem to fit without leaking; mine improved when warmed up with the gas, but I don't mind the burnt chrome!

regards martin

Thanks Martin some things to check on a miserable wet day in June.

Submitted by peter_denham on Wed, 22/06/2016

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Previously peter_denham wrote:

Previously Martin Freeman wrote:

Sounds like you have a leak on your exhaust, so check tightness of all joins, I have found original silencer clamps not up to job;try some of thes, but measure silencer carefully for OD

http://www.ebay.co.uk/itm/MIKALOR-W2-Stainless-Supra-Heavy-Duty-Exhaust-Pipe-Clip-Hydraulic-Hose-Clamp-/271326260811?var=570217368578&hash=item3f2c4e2e4b:m:m_9MZJyXp3KuvXH7oK3SnVw

If you have exhaust with balance pipe they never seem to fit without leaking; mine improved when warmed up with the gas, but I don't mind the burnt chrome!

regards martin

Thanks Martin some things to check on a miserable wet day in June.

PS:- Clamps ordered.

Submitted by robert_tuck on Wed, 22/06/2016

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You said you have a missfire, a leaky exhaust will pop but also an excess of fuel in the exhaust from a missing plug will ignite in the exhaust too.Look at the plugs , one very sooty one?.

Submitted by peter_denham on Wed, 22/06/2016

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Previously robert_tuck wrote:

You said you have a missfire, a leaky exhaust will pop but also an excess of fuel in the exhaust from a missing plug will ignite in the exhaust too.Look at the plugs , one very sooty one?.

Yes one sooty one will change It tomorrow thanks.

Submitted by robert_tuck on Thu, 23/06/2016

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Might just be a bad plug, but equally may be bad plug cap or lead, coil ,coil connections, capacitor( if you have points ). Valve seal,etc. Whats the bike and the ignition system?.

Submitted by peter_denham on Thu, 23/06/2016

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Previously robert_tuck wrote:

Might just be a bad plug, but equally may be bad plug cap or lead, coil ,coil connections, capacitor( if you have points ). Valve seal,etc. Whats the bike and the ignition system?.

Many thanks Guys it was a duff plug two bad plugs in as many weeks and one an NGK!!!!!!! THANKS TO ALL Pete.

Submitted by dave_taylor on Sat, 06/08/2016

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Previously peter_denham wrote:

Previously robert_tuck wrote:

Might just be a bad plug, but equally may be bad plug cap or lead, coil ,coil connections, capacitor( if you have points ). Valve seal,etc. Whats the bike and the ignition system?.

Many thanks Guys it was a duff plug two bad plugs in as many weeks and one an NGK!!!!!!! THANKS TO ALL Pete.

Peter,

If the motor keeps fouling plugs you might need to fit a new pair one grade hotter until you fathom out the cause.

Dave

Submitted by peter_denham on Sun, 07/08/2016

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Previously dave_taylor wrote:

Previously peter_denham wrote:

Previously robert_tuck wrote:

Might just be a bad plug, but equally may be bad plug cap or lead, coil ,coil connections, capacitor( if you have points ). Valve seal,etc. Whats the bike and the ignition system?.

Many thanks Guys it was a duff plug two bad plugs in as many weeks and one an NGK!!!!!!! THANKS TO ALL Pete.

Peter,

If the motor keeps fouling plugs you might need to fit a new pair one grade hotter until you fathom out the cause.

Dave

Thanks Dave have two dissimilar heat range plugs in and is running sweet as a nut so just enjoying the ride!!!!

Submitted by les_howard on Mon, 08/08/2016

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I wonder what ignition system you have fitted?

Some electronic systems fire the plug every revolution which might be igniting some excess fuel on the over-run..

Otherwise it's an exhaust air-leak.

Les

Submitted by david_evans on Mon, 08/08/2016

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A leak in the exhaust should have little to do with popping on the overrun. More likely to be an intake system leak between the carb and the head. The popping is fuel being ignited drawn in by the suction created with a closed throttle valve, (via the pilot jet i.e. down stream of the throttle valve) prove it by brushing petrol on the joint with the engine running and see if the tickover rises. (stand by with a fire extinguisher)Cry

Submitted by peter_denham on Tue, 09/08/2016

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Many thanks for all the replies I think I have Her running as good as I can get with old carb bodies I will start saving!!!!!

 



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