I broke down.......again!

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Iand
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I broke down.......again!

Unread post by Iand » Mon Mar 26, 2012 9:16 am

I went out for a short run on the bantam, just up to Onyerbike near Waddesdon, on my '54 Bantam. It coughed and spluttered a bit on the way, after around 6 miles, but got there no problems. It then started up 2nd kick to come home after stopping for about 45minutes. I got about 500yds up the road when it coughed spluttered and refused to start.
Pulled over, no tool kit, 2 fellas I was chatting to stopped - one had a pair of pliers, so i pulled the spark plug, colour looked ok and it wasn't not too wet either. Checked for spark, yes but quite weak. Checked for fuel, yes running fine. hmmmmm......
One of the fellas who stopped was on an immaculate kawasaki H2 750, he has a spare set of plugs, which fit. Fires up 2nd kick again.

Why would my plug just suddenly stop working?

IanD
1960 lambretta Li125 sold; 2001 Honda CG125 sold; 2006 Yamaha FZ6 sold; 1980 Kawasaki Z500 sold; 1967 BSA Bantam D10; 2008 Aprilia Shiver sold; 2010 KTM Duke 690R; 1954 BSA Bantam; 1980ish Kawasaki Z200

Buckinghamshire, UK

Paul in NZ
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Joined: Thu Mar 22, 2012 9:51 pm
Location: Kapiti New Zealand.

Re: I broke down.......again!

Unread post by Paul in NZ » Mon Mar 26, 2012 10:07 pm

Assuming you have the mixture and oil content right, maybe the spark is weak? Especially when the bikes hot??

Don't they have some kind of flywheel magneto / ignition thing? They do get weaker with age.
He who hears not the music thinks the dancers mad....

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Iand
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Re: I broke down.......again!

Unread post by Iand » Mon Mar 26, 2012 10:21 pm

Paul in NZ wrote:Assuming you have the mixture and oil content right, maybe the spark is weak? Especially when the bikes hot??

Don't they have some kind of flywheel magneto / ignition thing? They do get weaker with age.


Yes I guess they do, but I still had a spark on the old plug, and a brighter spark with the new (2nd hand Kawasaki H2 750) plug? That's the bit I don't understand, my boss reckons it may have been running rich and just clogged the old plug up, reducing the strength of the spark.
1960 lambretta Li125 sold; 2001 Honda CG125 sold; 2006 Yamaha FZ6 sold; 1980 Kawasaki Z500 sold; 1967 BSA Bantam D10; 2008 Aprilia Shiver sold; 2010 KTM Duke 690R; 1954 BSA Bantam; 1980ish Kawasaki Z200

Buckinghamshire, UK

Paul in NZ
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Location: Kapiti New Zealand.

Re: I broke down.......again!

Unread post by Paul in NZ » Mon Mar 26, 2012 10:34 pm

Well yes of course which is why I said IF the mixture / oil content was correct.

The plug needs to get hot enough to be self cleaning (like on a 4 stroke). Modern 2 stroke oils are usually better so you can run a leaner mix and modern fuels burn slower than older fuels. I find all my old 4 strokes run rich on factory settings at low speed.

Its simple enough to check the carb has the correct jets, the air filter is clear etc so I'd start there. Also look at the exhaust amd check its not clogged up and never leave home on an old stroker without a spare plug and spanner...
He who hears not the music thinks the dancers mad....

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Iand
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Re: I broke down.......again!

Unread post by Iand » Tue Mar 27, 2012 10:18 am

I your probably right, I need to use a weaker mix, I'm still going around 30-35 to 1, speaking to a few people the other day they reckon I can go to 50 to 1, I'll give it ago to see how I get on.
It'll always give me an excuse to vote out and tune the engine if it goes pop!!

IanD
1960 lambretta Li125 sold; 2001 Honda CG125 sold; 2006 Yamaha FZ6 sold; 1980 Kawasaki Z500 sold; 1967 BSA Bantam D10; 2008 Aprilia Shiver sold; 2010 KTM Duke 690R; 1954 BSA Bantam; 1980ish Kawasaki Z200

Buckinghamshire, UK

DerryUK
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Re: I broke down.......again!

Unread post by DerryUK » Tue Mar 27, 2012 5:02 pm

<without a spare plug and spanner>
I’d agree with that.

I would change your plug and capacitor (condenser). Both can suffer when they get hot.

Also, not starting when hot can be a sign of a rich mixture. Remember you need a richer mixture to start when cold (choke or flood the carb) so when hot the reverse is true.

Playing around with your petrol/oil mix will also change your mixture strength. If you have less oil in your petrol it means more petrol will flow through a jet and give you a richer mixture.

Derry.

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