Misc: Everything Else Misfire

nigsey

nigsey

Well Known and Active Forum User
VOC Member
Have a slight misfire, mostly when accelerating on my C twin, wondering if it could be a blocked carb jet. Carbs are Amal 276’s with Vokes air filters, currently running on Esso Supreme 99. Ticks over fine, new NGK plugs fitted, see photo, only done 90 miles on them. Any ideas please as to what might be causing the misfire.
 

Attachments

  • 12DEF05F-A7BA-45D5-804B-66B0E4E8CE6B.jpeg
    12DEF05F-A7BA-45D5-804B-66B0E4E8CE6B.jpeg
    168.3 KB · Views: 50
greg brillus

greg brillus

Well Known and Active Forum User
VOC Member
Do not run premium unleaded fuels with older carburetor engines. They will run very sooty pugs.........run 91 to 95 max octane fuels, definitely not premium.
 
nigsey

nigsey

Well Known and Active Forum User
VOC Member
Bill Thomas said:
Looks like one of mine !, I like them a bit rich /oily,
Have you got solid H.T. leads ?, What ignition are you running ?.
You only want about 20 thou plug gap ?.
If you have supresser caps ?, Take them off ?.
Click to expand...
Thanks Bill, I’m running a BTH mag with flexible leads. Plug gap is the factory set one 30 thou, so I’ll reduce that to 20. I guess it must be running rich, doesn’t appear to be any black smoke from the exhaust but I noticed a substantial sooty mark on the wall behind the bike when I started it up the other day.
 
Bill Thomas

Bill Thomas

Well Known and Active Forum User
VOC Member
I thought we had this before ?, 30 thou is too much ??,
After start up you are bound to have soot ?, After flooding or choke ?.
I have had a lot of trouble with NGK plugs,
I only use champion N5 or N9y, They put a c on them now , but that's OK, = Copper ?.
Do you drive very steady ? , Maybe needs a few rev's to clear it out.

If I have trouble with a plug, I put it in the BIN,
Not worth the worry.

I would do a plug test after a steady 70 mph ish ,
I don't like them weak !.
Most of the time your on the slide ?.
 
nigsey

nigsey

Well Known and Active Forum User
VOC Member
Bill Thomas said:
I thought we had this before ?, 30 thou is too much ??,
After start up you are bound to have soot ?, After flooding or choke ?.
I have had a lot of trouble with NGK plugs,
I only use champion N5 or N9y, They put a c on them now , but that's OK, = Copper ?.
Do you drive very steady ? , Maybe needs a few rev's to clear it out.

If I have trouble with a plug, I put it in the BIN,
Not worth the worry.

I would do a plug test after a steady 70 mph ish ,
I don't like them weak !.
Most of the time your on the slide ?.
Click to expand...
I bought the bike with NGK plugs in it, so carried on with them. I use choke on first start up and take it off more or less straight away, always flood the carbs but not excessively. Engine is always a little lumpy on first start up. I’m a steady driver, 50 for the first few miles then up to 60 or so but never over 70. Not sure what you mean about on the slide?
 
Bill Thomas

Bill Thomas

Well Known and Active Forum User
VOC Member
Sorry. Job to know how much people know.
The cutaway on the carb slide
Makes a lot of difference.
With a twin that's where the throttle is
Mostly. Up to 80 mph on mine
I have had to weaken the slides
With this petrol ie bigger cutaway.
But don't rush into anything yet.
 
Top