1966AJS 250 CSR WEAK SPARK

[valori]

I'm intrigued by this problem. I've had a 1965 AJS 250 CSR for the last 2.5 years. It has always been a problem to start except when it has been running.It also tends to "pop" on deceleration. I haven't changed as many electrical parts yet and will check the ignition timing. I will certainly try any solution BofN finds.
Any further thoughts,please

[bag-o-nails]

some sucsess i went to battles bridge classic bike show today and got talking to a chap selling eleltrics when i told him about the problem he claimed it's the plug cap he produced a low resistence unsurpressed cap
made by NGK it cost £2.00 soon as i got home
on it went second kick the engine burst in to life i then left it for an hour and again sucsess!! YA hoo

[paul knapp]

G'day Robert,
Popping on deceleration is the unburned fuel detonating in the exhaust. Too rich a fuel mixture in the carburettor primary circuit, coupled to either retarded ignition/hot exhaust/air leaks are a probable cause.

Paul
...........
I note, the 'curse of the suppression plug cap' appeares to have struck again!

...Edited by - paul knapp on 02 Jul 2007 01:49:53 AM

[chris kelly]

Hi ,

"Short reach -- never "

Well, thats true, Long Reach it is.

I am pleased that Phil has got the solution but intrigued that some of our more expert members did not suggest this.

However, just this second ,looking in a book by David Frost, "Motor cycle care and maintenance"

He writes,"This suppressor eliminates radio interference . It will not affect the performance unless you happen to have a very weak spark for some reason or other, when removal of the suppressor will give you just that little extra spark that makes all the difference. But remember to replace the suppressor as soon as you can if you want to keep friends with your neighbours."

Well, the book was printed in 1961 !

Best wishes, Chris.

[valori]

Text
Thanks Paul & B of N - I'll give them a try

[Biscuit]

As a magneto devotee, I thought coil ignition (dammit) could handle suppressors. My magneto can handle the built in suppressor on iridium plugs. Perhaps there still is a fault there.

[bag-o-nails]

Hi Alan
when did they fit mageto's to 250's i am sure
the three coil's of the alt could not light up
an iridium plug even on max output
i have just fitted a new carb the plug is still
a bit sooty! any idea's, could it be the barrel
piston or head or all three are standard 250
and not csr how would i check that? i did not
see any number's when i had the head off
cheers

[Biscuit]

Magneto's were, of course, never fitted to lightweights I was merely pointing out that on my G11 and G3 the magneto adequately deals with surpressed iridium plugs, and if this is the case, coil ignition would have no problems.

It is not the alternator that 'fires up the plugs' it is of course the battery, so the method of charging, alternator or dynamo, has absolutely no bearing on the matter.

[bag-o-nails]

that's interesting l aways thought the battery
only stored current for initial start up d/c and then a/c is supplied from the alt through the rectifier and trickle charges the battery on three coils and then six for the
lights or emg controlled through the sw
must be where i am going wrong
the reason i ask about the head/barrel/piston
if it is only a 250 and not csr it will not cope with the mixture a csr carb will deliver, result sooty plug flooding, dirty plug leading to a weak spark i am sure it is not electric's all the
commponent's L/T H/T have been replaced
including the alt and rect.
cheers Phill

[itma]

the carb differs only on the jetting if at all .