Misc: Ignition Mysterious Meteor misfire - what am I missing?

greg brillus

Well Known and Active Forum User
VOC Member
I've had similar problems with the newer Amal Premier concentric's on a few different bikes.......Yes the needle fails to lift via the float.........had one bike were you could hold the tickler down and nothing would happen. Had to bend one of the float tangs to actually lift the needle off its seat when the float lowers........Never been a fan of concentics, they have always been a very poorly made carb in my opinion.
 

CoreyL

Well Known and Active Forum User
VOC Member
I had something similar and it was fuel starvation, I found the float was fouling the float bowl before lifting the float needle, but it was taking pressure off the needle so you would expect fuel to flow, it did, but not enough so I phoned AMAL.
They explained to me the brass viton tipped needle was too heavy to be lifted properly with fuel pressure alone and now supply an alloy needle for this problem, just something to check.

Strangely it came on suddenly, the carb had been on over 1500 miles before this started, I had other problems with it around this time and haven't used the bike for 2 years so can't remember if I used it much after or not.
I have the rubber tipped alloy float needle in there already.
 

LoneStar

Well Known and Active Forum User
VOC Member
Sediment in the float bowl, intermittently blocking main jet. Or bad gas - as you say, why would it take so long to manifest? But it's easy to replace the fuel and see for sure.
 

vibrac

Well Known and Active Forum User
VOC Member
There is a lot of 'folk law' on many threads here about the concentric carb I am not alone in disliking them beg or borrow another carb and just see what happens
 

CoreyL

Well Known and Active Forum User
VOC Member
Sediment in the float bowl, intermittently blocking main jet. Or bad gas - as you say, why would it take so long to manifest? But it's easy to replace the fuel and see for sure.
I drained and refilled the tank yesterday with fresh fuel - no improvement.
 

oexing

Well Known and Active Forum User
VOC Member
Your last check ride was allright for half an hour ? Seems time is the factor so my idea is to check sparks on the plug wire AFTER half an hour ride for max length . Electronics and coils are notorious for defects in hot state so no luck when checking at cold .

Vic
 
Last edited:

LoneStar

Well Known and Active Forum User
VOC Member
Does the misfire occur with a cold engine, or only after everything is hot? It idles well; does the misfire begin at a certain rpm, or with a certain throttle opening? Only under load, or revving in neutral?
 

CoreyL

Well Known and Active Forum User
VOC Member
It seems to worsen as the engine warms up. It doesn't seem to be RPM-related. I haven't tried revving in neutral. It doesn't seem to matter if the engine is under load or not.

My attention is focused on the BTH unit now. Maybe a bad earth connection or something like that? I'm going to remove the mag cover and poke around and see what I can see...
Does the misfire occur with a cold engine, or only after everything is hot? It idles well; does the misfire begin at a certain rpm, or with a certain throttle opening? Only under load, or revving in neutral
 
Top